COMPOSITES THEORY AND PRACTICE

A refined, fully analytical rheological modelling of thermosetting polymers and unidirectional monotropic fibrereinforced thermoset matrix (UFRT) composites is presented. New polymers and composites under normal conditions, fully relaxed from curing and post-curing stresses, are modelled. The theory includes quasi-static short-term/medium-term/longterm reversible rheological processes. Thermosets are isotropic materials exhibiting linearly viscoelastic shear strains and linearly elastic bulk strains. Fibres are monotropic (transversely isotropic) and linearly elastic materials. A generic function well reproducing the viscoelastic characteristics of thermosets and UFRT composites is a Mittag-Leffler fractional exponential function in an integral form. Coupled/uncoupled standard/inverse constitutive equations of linear rheology are formulated for thermosets and UFRT composites. The equations are mutually analytically transformable. New rheological models (coded H-R/H) for thermosets and UFRT composites are described by the smallest possible number of material constants. The thermoset is described by two independent elastic constants and three independent viscoelastic constants. The homogenized UFRT composite is described by five independent elastic constants and four independent viscoelastic constants, whereby two viscoelastic constants are common to the matrix and the composite. An improved homogenization theory of UFRT composites, based on analytical solutions of the selected tasks of the theory of linear elasticity, is formulated for monotropic fibres and positively validated experimentally. The viscoelastic constants of the thermoset are calculated analytically in an iterative loop using a long-term unidirectional tension creep experimental test. The viscoelastic constants of the UFRT composite are calculated analytically employing H-R/H shear/quasi-shear storage compliances and VECP (the viscoelastic-elastic correspondence principle) shear/quasi-shear storage compliances. The H-R/H rheological model was validated numerically for selected UFRT composites. The validation tests were performed on the enhanced reliability UFRT composites reported by Soden, Hinton, and Kaddour (Composites Science and Technology, 1998, 2002).

This paper is the first of two parts of a pioneering study to evaluate the effect of the strain rate of a GFRP laminate on the stress response. The assessment concerns the elastic range of deformation only. The publication contains the assumptions and methodological description of the conducted experiments. The non-destructive bending tests and the methodology for determining the modulus of elasticity and the energy of the load-unload cycle are presented in detail. The full set of test results is presented in the appendix. The results and conclusions are discussed in the second part of the study, which is a separate publication.

This article presents a comparison of the properties of composites based on aluminum or aluminum alloy (Al4Cu) reinforced with silicon carbide SiCp. The main objective was to analyze the possibility of producing an Al + Cu alloy matrix by basic powder metallurgy methods and its influence on the final properties of the composite. The composites were produced by pressing and sintering, basic powder metallurgy techniques, in order to reduce the manufacturing costs. Sintering was carried out in nitrogen due to the favorable effect of this atmosphere on the sintering of aluminum-based materials. Silicon carbide SiC was used as the reinforcing phase. The study clearly showed that the use of a matrix made of a mixture of Al and Cu powders results in an almost twofold increase in hardness (from 32 to about 60 HB) and a more than twofold increase in flexural strength (from about 200 to more than 450 MPa). Observations of the microstructure confirmed the diffusion of copper into the aluminum and the facets of the Al2Cu phase.

In the contemporary research community, hybrid composites with improved performance are merging as a trend, overcoming the drawbacks of conventional composites and satisfying needs in tribological applications. In this work, Al-MHA-Si3N4 hybrid composites reinforced with various weight percentages of mustard husk ash (MHA), 0, 2.5, 5, 7.5% and 10%, produced by powder metallurgy techniques at 300, 400, 500, 600 and 700 MPa compaction pressure were analysed. The microstructural characterization of the metal matrix hybrid composites, followed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) investigations show the homogeneous distribution of the reinforcement in the metal matrix. A sliding wear study without lubrication was performed on a pin-on-disc wear testing machine under the following sliding conditions: sliding velocity (SV) of 1.5 m/s, sliding distance (SD) of 300 m and applied loads of 25 N and 35 N. The deformation of the worn surfaces was also investigated. It was found that the tribological characteristics of the composites were enhanced by increasing the weight percentage of MHA and the compaction pressure.

This paper is the second part of the study aimed at evaluating the influence of the strain rate of the plain weave reinforced GFRP laminate, in the non-destructive static three-point bending test, on the material’s stress response. It was found that the stress level during the entire course of the deflection increases with the increase of the strain rate. The relative change in the stress level is comparable for the 0/90 and 45/45 fiber orientations. As the loading speed increases, the elastic modulus of the material also increases. For an increase in the strain rate from 1.11∙10-3 to 5.57∙10-1 1/s, the increase is 10% for the 0/90 fiber arrangement and 17.7% for the 45/45 fiber arrangement. The dependence of the modulus on the strain rate is logarithmic. Based on the theoretical analysis, the cause of the observed effects of the strain rate on the material response was attributed to the viscoelastic behavior of the matrix (cured polymer resin) and the viscoelastic behavior of the fibers system at the level of the laminate mesostructure.

The present study focuses on the fabrication and characterization of novel hybrid Al matrix composites with a combination of two ceramic reinforcements, i.e. Al2O3, SiC and one solid lubricant, i.e. WS2. This hybrid composite was fabricated by means of the powder metallurgy process. The impact of the hybrid combination of reinforcements in different wt.% on the properties of the hybrid composites was studied. The density of the composites increases from 2.689 to 2.796 g/cm3 with an increase in wt.% of WS2. Uniform distribution of the reinforcing particles in the matrix phase was determined by SEM. The results of, for instance, density measurements and microstructural analysis indicate significant improvement in the physical and mechanical properties with the increase in the wt.% of WS2. The microhardness of the as-fabricated composites rises from 98 HV to 119.7 HV with the increase in the wt.% of WS2 from 0 to 6 wt.%. The novel combination of Al with SiC, Al2O3 and WS2 can be used to create a suitable and sustainable hybrid metal matrix composite for the automotive industry as a replacement for single ceramic and single solid lubricant composites.

A study was conducted on selected nanoclay fillers, i.e. montmorillonite (MMT) or halloysite (HNT) in polylactic acid (PLA) pellets for the manufacture of filaments for 3D printing. A 1-3 weight fraction of the filler was used. In order to compatibilize the nanofiller with the PLA, two methods were employed to facilitate dispersion of the nanoclay particles: using prewetting of the nanoclay in dichloromethane (DCM) and introducing a short-chain plasticizer (polyethylene glycol, PEG200) during the homogenization process. The effectiveness of filler dispersion was verified by performing thermal analysis, i.e. thermogravimetry and differential scanning calorimetry (DG/DSC), as well as by microscopic observations. The processability of the obtained nanocomposite filament was verified for the finished products manufactured from both of the materials by FDM printing. Mechanical strength and impact tests were conducted on the printed samples. The results showed that the prints made from the nanocomposite filaments have better tensile strength (by 25 and 10% for PLA/HNT and PLA/MMT, respectively) compared to prints made from the pure polymer filament.

Lightweight aggregates developed on the basis of hydraulic binders and mining waste were investigated in the study. Original technology was utilized to obtain the aggregates. The synthetic aggregate materials obtained in the work satisfy the basic requirements for materials used in construction. Granulates were obtained by granulating raw materials with a counter-current high intensity mixer having a nominal capacity of 30 litres. A rotary tube furnace was selected as the most appropriate to sinter the produced granulates. The process combined two operations: burning the combustible fractions (sewage sludge) responsible for porosity, and sintering (consolidating) the granulate. The sintering process was conducted at the temperature of 950°C in the presence of air. The working reactor tilt was about 2°. Initially the rotational speed for the quick tests was 4.28 rpm, which yielded a granule residence time of about 7.3 minutes in the heating zone (a variant was applied for the tests). The obtained aggregates were subjected to strength testing, and their crushing resistance was determined based on standard PN-EN 13055-1. Depending on the proportions of the individual raw materials, the aggregates are characterised by high crushing resistance from 4.1 to 6.5 MPa, which confirms the potential for their industrial application. These aggregates may be used for purposes such as lightweight building and pavement concrete production due to their relatively low bulk density.

Natural fibres are used to develop green composites due to their environmentally friendly nature, ease of availability, low cost, higher strength, as well as good thermal, acoustic, and insulating properties. In this study, jute fibre (JF) and sisal fibre (SF) were considered as reinforcement and a biodegradable polymer, namely polylactic acid (PLA), was selected to fabricate the composites by the injection moulding process. The fibres were chemically treated with sodium hydroxide (NaOH) at a concentration of 2% to improve the characteristics of the fibre. The effect of the injection moulding parameters like injection pressure (bars), injection speed (mm/s), and melting temperature (°C) on the tensile and flexural properties of the sisal fibre/polylactic acid (SF/PLA) and jute fibre/polylactic acid (JF/PLA) composites were investigated. Taguchi’s L9 orthogonal array was chosen for the design of experiments, and analysis of variance (ANOVA) was performed to find the significance and contribution of the selected parameters. The optimum levels from the main plots of both the tensile and flexural strength of the JF/PLA composite were found to be the injection pressure of 90 bars, injection speed of 60 mm/s, and injection temperature of 165°C. Meanwhile, the optimum level of tensile strength for SF/PLA-based composite was recorded as the injection pressure of 70 bars, injection speed of 40 mm/s, and temperature of 165°C. For the flexural strength, the optimum level was determined as the injection pressure of 90 bars, injection speed of 60 mm/s, and temperature of 165°C.

This current paper, which is the first part of two parts of a complete article, presents the theoretical and finite element formulation developed and proposed by the authors to obtain the stress concentration factors (SCFs) and the first ply failure (FPF) loads of composite laminated plates. The numerical studies are performed using a quadrilateral finite element of four nodes with thirty-two degrees of freedom. The present finite element was previously developed by the authors to study the bending and buckling of composite plates. The present finite element is a combination of two finite elements. The first one is a linear isoparametric membrane element, and the second one is a high-precision rectangular Hermitian element. In the second part of the paper, several examples will be considered to demonstrate and affirm the accuracy and the performance of the present element, as well as highlight the effect of some parameters on the stress distribution. The FPF strengths and their locations in laminated plates with and without holes are calculated by adapting the Hashin-Rotem, Tsai-Hill, and Tsai-Wu failure theories.

This paper presents the process of manufacturing bimetallic composites in the shell-core system. Al17Si5Fe3Cu1.1Mg0.6Zr alloy powder was used for the shell. Pure aluminum was used as the core of the composite, respectively, in the form of a cast and then rolled rod, and in the form of a semi-finished product obtained from aluminum powder. The semi-finished powders were produced by means of the uniaxial hot pressing method. From the components prepared in this way, an extrusion charge was made by machining in an alloy shell-core system. Permanent bonding of the components and forming the required shape of the composites was carried out using direct hot extrusion under isothermal conditions. It was confirmed that the application of powder metallurgy technology for the production of one or both component materials makes it possible to conduct the extrusion of the components with significantly different plasticity without violating the cohesion of the layers. This approach made it possible to produce layered composites with high-strength properties of the outer layer and with a ductile core. The microstructural state of the components was evaluated, focusing on the continuity of the transition zone between the components. Observations of the separation lines between the layers revealed that the zone between the components was continuous, which was found for both composites, regardless of the examined cross-section. On this basis, it was concluded that the direct hot extrusion process, carried out under the adopted parameters, made it possible to combine the components very well. Selected properties of the layered composites were also determined. It was shown that the proposed method, combining powder metallurgy and hot forming technologies, makes it possible to obtain a continuous connection of components and produce products with properties significantly differentiating in the core and shell zones. These properties can be controlled by appropriate selection of the components, as well as by the method of manufacturing the core. Potential applications of the studied materials include the manufacture of bimetallic components for operation in conditions where significantly different properties of the outer zone and the core are required.

The stir casting process was used to produce AZ91D magnesium alloy hybrid composites reinforced with boron carbide (B4C) and zirconia (ZrO2). The microstructure of the composites revealed heterogeneity in the reinforcing phase distribution. A pin-on-disc test was conducted to investigate the tribological features of the fabricated composites such as the wear and coefficient of friction under dry sliding conditions. Increased hardness was observed for the composites due to the dispersion of the reinforcement. The composite with 2 wt.% ZrO2 + 3 wt.% B4C exhibited a higher yield strength and increased tensile strength compared with the other specimens. It was observed that the addition of B4C and ZrO2 improved the wear resistance of the AZ91D alloy as reflected by the lower wear rate. Among all the specimens, the composite reinforced with 2 wt.% ZrO2 + 3 wt.% B4C has the highest wear resistance. Hence, it can be concluded from the present work that incorporating B4C and ZrO2 is a promising way to achieve better mechanical properties and wear properties of AZ91 composites.

This paper, the second part of two parts of a complete paper, presents the analytical and numerical results of stresses around circular cutouts in anisotropic and isotropic plates under shear loading. The main aim of this study is to understand the effect of the presence of cutouts on the stress concentration and failure mechanisms in composite laminates. The numerical investigations are performed by means of the quadrilateral finite element of four nodes with thirty-two degrees of freedom. The present finite element is a combination of two finite elements. The first one is a simple linear isoparametric membrane element and the second one is a high-precision rectangular Hermitian element. The analytical and finite element formulations were presented in the first part of the paper. Several new examples are considered to demonstrate and affirm the accuracy and the performance of the present element and to highlight the effect of some parameters on the stress distributions. The numerically obtained results are found to be in good agreement with the analytical findings. On the other hand, first ply failure (FPF) strengths in laminates with and without holes are calculated by adapting the Hashin-Rotem, Tsai-Hill, and Tsai-Wu failure theories. Finally, the numbers of the figures are obtained, using various E1/E2 ratio values, for the maximum positive and negative stresses values located in the vicinity of the cutout versus the angular location of points, and for various fiber orientation angles.

In the past few decades, natural fiber reinforced polymeric composites have gained significant importance for various structural applications in different sectors like the automotive, aerospace, sports and building construction industries. However, hybridizations make the composite more versatile in term of strength, weight and its processing for many engineering applications. In the current study, a polyester resin matrix was reinforced with two different natural fibers, namely kenaf and palmyra palm leaf stalk (PPLS) and hybridized with glass fiber. Four layers of two different fiber mats, kenaf/glass and PPLS/glass with different stacking sequences were employed to fabricated laminates by the hand lay-up technique. In this case, an attempt was made using the numerical approach to investigate the influence of glass fiber on the mechanical characteristics of the laminates. To substantiate the results of the numerical approach, experiments were conducted. Enhancement of both the tensile and flexural strength was observed due to hybridization of both the kenaf and PPLS fiber with glass fiber. The tensile and flexural strength improved by 68.91 and 37.63% respectively when the kenaf fiber was hybridized with glass fiber. Similarly, enhancement of 54.42% of the tensile strength and 15.92% of the flexural strength were noticed when the PPLS fiber was hybridized with glass fiber. Through the use of ANSYS software, finite element analysis (FEA) was employed as a simulation method to examine the tensile and flexural strength. The numerical findings were found to be quite close to the experimental results, with a variation of less than 3%.

The bimaterials applied in various fields of industry consist mainly of ceramics and metal. Their damage is mainly due to the presence of residual stresses generated during their manufacture. The damaged area is closely related to the high production temperature. The aim of this study is to analyze the effect of these factors on the behavior of an interfacial and subinterfacial crack in the volume of alumina material. This behavior is studied in terms of variation of the stress intensity factor (SIF) in Modes I, II and III. A study by means of the finite element method (FEM) was carried out. This work demonstrates that the risk of sudden propagation of these cracks is all the more probable when the bimaterial is produced at high temperatures. The elastoplastic behavior of the metal considerably minimizes this risk by plasticizing the metal, which allows strong relaxation of the residual stresses.

In this paper, hollow glass microspheres (HGMs) were surface treated using a silane coupling agent to coat the surface with an amine functional group. Modified and unmodified HGM filled polycarbonate (PC)/acrylonitrile butadiene styrene (ABS) (70/30 wt.%) composites were prepared using a twin-screw extruder and then injection moulding. By means of FTIR spectroscopy, it was found that the modified HGMs containing the amine group formed an aminolysis compound with the PC phase. Scratch studies were performed at low load to avoid fracturing the composites during the test so that deformation of the material only happened in order to understand the influence of HGMs and modified HGM on the scratch behaviour of the composites. The silane modified HGM filled PC70/ABS30 composites exhibited improvement in scratch behaviour as compared to the composites containing unmodified HGMs. The 5 wt.% HGM-NH2 filled PC70/ABS30 composites demonstrate good improvement in scratch resistance as they attained the the highest values of scratch force, coefficient of friction and scratch hardness among all the compositions of composites.

In this work, the compression strength of bamboo reinforced low-density polyethylene waste (water sachet waste) composites was predicted. The composites were produced using the compression moulding technique with the following formulations: LDPEw, 5, 10, 15, and 20 wt.% filler. The hardness and compression strength of the examined composites were found to increase when the amount of filler was raised, with the formulation containing 20 wt.% filler having the highest hardness and compression strength values of 59.37 HV and 12.72 MPa, respectively. The control (LDPEw) gave the lowest values of hardness (41.57 HV) and compression strength (8.6 MPa). Multiple regression (MR) and artificial neural networks (ANN) were utilized to predict the experimental compression strength of the produced composites with the hardness and filler composition as independent variables. The mean squared error results indicated that when compared with the multiple regression forecasts, the artificial neural network predictions not only had smaller errors but were also closer to the experimental compression strength values. It is recommended that other methods of producing composites, such as the pulverization process with a 40% higher filler content than what was used in this work, should be studied to ascertain if they provide better composite materials.

The current study aims to investigate at the tribological properties of Al7050 reinforced with TiO2 and BN particles utilising a pin-on-disc apparatus. By means of the stir-casting process, MMCs were fabricated with three different weight percentages of TiO2 particles: 1, 3, and 5%, as well as various weight percentages of h-BN particles: 2, 4, and 6%. The volumetric wear rates and coefficients of friction were continuously recorded under normal loads of 20-40 N, sliding speeds of 2-4 m/s and for sliding distances of 1000, 1500 and 2000 m. Microstructural analysis revealed that the TiO2 and BN particles were uniformly dispersed throughout the Al7050 matrix with minimal agglomeration. The experimental data reveals that the tensile strength and Vickers hardness of the cast hybrid composites gradually improved by increasing the weight percentages of the TiO2 and h-BN reinforcing particles. The worn micrographs reveal that abrasion and delamination are the dominant wear mechanisms in the case of the hybrid composites. The composite containing 6 wt.% h-BN particles had the lowest coefficient of friction and wear rate at a normal load of 40 N, sliding speed of 4 m/s and for the sliding distance of 2000 m when compared to other composites. On the other hand, the composites with 2 wt.% h-BN particles had the highest coefficient of friction and wear rate. The XRD analysis showed the generation of strong interfacial reactions, which contributed to the hardness of the hybrid composites.

Thermally insulating lightweight plasters are urgently needed for the development of sustainable energy-saving buildings. The creation of such a material is possible because of the use of lightweight fillers, which are of interest to many researchers. As a result of their porous structure, it is possible to lower the density and thermal conductivity of various materials. The aim of this work is to analyze the influence of hollow glass microspheres in two granulations and expanded glass on the parameters of polymer plaster. Composites containing various amounts of lightweight fillers were prepared. Then, their parameters were compared in terms of the mechanical properties, thermal conductivity, vapor permeability, and water absorption. All three lightweight fillers successfully reduced the density of the polymer mass and improved plaster insulation. The best effect was achieved with both types of hollow glass microspheres. The weight of the polymer binder was reduced by up to 80%. In the case of expanded glass, the density was only reduced by 38%. At the same time, the composites were studied in terms of their mechanical and moisture properties. The specimens with the highest amount of lightweight filler showed significant deterioration in elasticity due to disturbance of the pigment:binder ratio. They cracked at lower deflection angles. By not exceeding 20% of the filler, no effect on flexibility was observed in any of the three investigated fillers. Interpretation of the research results indicates that the studied lightweight fillers allow a plaster mass to be obtained with an extremely low thermal conductivity coefficient, less than 0.086 W/mK. However, while ensuring the optimal proportion between fillers and polymer binder, it is possible to reduce the coefficient to 0.261 W/mK without noticeable deterioration of the mechanical properties.

This paper presents a description of the temperature changes that take place in the curing system of polymer concrete. The research used polymer concrete composed of 30% by volume unsaturated polyester resin acting as a binder for powder fillers. Among the powder fillers, ground glass waste and sand in a volume ratio of 1:1 were used. The investigations were carried out for three volumes, 10, 100 and 1000 cm3, respectively. The temperature in the central point of the volume (the highest temperature) was measured by the ATD method using a NiCr-NiAl thermocouple, and the temperature on the polymer concrete surface was measured using a thermal imaging camera. The temperature-time course recorded for both the measuring points allowed evaluation of the curing system parameters (gelation time, maximum curing temperature, time to maximumtemperature), important for the processing of polymer concrete. Additionally, the knowledge of the temperature curves enabled a mathematical description of the heat flow between the measuring points. The conducted studies proved that the volume of the mold is important for the maximum temperature and curing time. The work is a continuation of previous research focused on polymer concrete and is an extension of information oriented to the industrial aspect. Knowledge of the temperature peaks and curing time will allow adjustments to be made to the manufacturing processes.

Open-porous preforms from Al-Ti-C compounds were successfully ignited and synthesized by combustion synthesis in a microwave field. The reaction course and the temperature were remarkably affected by the preparation method and molar ratio of the substrates, as well as the position of the green sample in the microwave field generated by a single mode microwave reactor. The manufactured structures were characterized by SEM investigations. The addition of aluminum powder to the mixture moderates the reaction and temperature variations, allowing the course of synthesis in explosive mode to be avoided. Among the reported developed materials the following can be distinguished: Ti-Al intermetallics, titanium carbides and MAX phases belonging to the Ti-Al-C system. The prepared and selected Al-Ti-C preforms were subsequently infiltrated with an AlSi12 aluminum alloy by the squeeze casting method. The composite materials exhibit a relatively homogeneous microstructure with low residual porosity and a good reinforcement/matrix interface.

Composites have become a very important class of materials in our everyday life. In the present work, the effect of a copper wireframe structure in SiC particle reinforced copper matrix composites on the compressive strength and other physical properties was analysed. SiC particle reinforced copper matrix composites with and without a copper wireframe structure were fabricated by the powder metallurgy method and sintering was performed at 700°C in atmospheric condition. The copper wire used for making the wireframe structure has diameters of 0.2 and 0.3 mm. A scanning electron microscope (SEM) with magnification of 500X was used to characterize the sintered composites. In addition, hardness tests were performed on a Vickers hardness testing machine and compression testing was carried on a UTM machine. It was observed that the formation of Cu reinforced with 5-7 wt.% SiC and 0.1-0.2 wt.% copper wireframe structure composites was successful. It can be concluded that the hardness of the Cu-SiC composite rises with the increase in the wt.% of reinforcement, while the copper wireframe structure in the composite had a negligible effect on the hardness. However, the addition of the copper wireframe structure resulted in increased compressive strength.

In the following study the influence of the ultrasonic treatment of graphite and glassy carbon powder reinforcement on epoxy composites was examined. Sonication treatment was applied to ethanol dispersions of graphite and glassy carbon respectively. After ultrasound treatment the dispersions were dried at the temperature of 70°C. Subsequently, the graphite and glassy carbon powders were mechanically extracted. The produced powders were then analyzed – the grain size distributions of the pre- and post-treatment powders were compared. The results show that the grain sizes of the sonicated graphite decreased, while the glassy carbon particles were not significantly influenced. Epoxy resin composites were made with the pre- and post-treatment powders as reinforcement. The mechanical properties of the prepared composites were examined using a Brinell hardness tester and a tensile tester. The results show slight changes in the mechanical properties of the composites reinforced with the sonicated powders in comparison to the non-sonicated powders and the neat resin samples.

Plates of bidirectional jute/polyester composite material were manufactured by the contact molding method. These plates were cut to form notched test pieces 80x15x4 mm and immersed in water (1, 10, 30, 90, 180 and 270 days) in order to study the impact behavior of this material. The studied composite exhibited a water saturation limit after an immersion period of approximately 30 days, with Fickian diffusion of water within the material. Williams’ method based on linear elastic fracture mechanics was used to calculate impact toughness GIC, which is due to the intrinsic characteristics of the material.

The present study investigates the microstructural and mechanical properties of few layer graphene (FLG, 0.1 to 5 wt.%) and aluminium oxide (Al2O3, 4 to 20 wt.%) reinforced Al6061 matrix composites prepared via mechanical alloying (MA), uniaxial pressing and pressureless sintering. The effects of the amounts of Al2O3 and FLG were studied. MA was carried out at 300 rpm for 3 h in a planetary ball mill in argon atmosphere. The mechanically alloyed (MAed) powders were compacted via uniaxial pressing (400 MPa) and sintering (620°C, 2 h). The microstructural and mechanical properties of the Al-xAl2O3-yFLG powders and bulk samples were investigated via X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Archimedes’ method and a hardness test. In the XRD analysis, the aluminium carbide (Al4C3) phase was not detected. The SEM, LM micrographs and EDS results show that the produced composites have a homogeneous structure. Based on the Archimedes’ method, the densification rates of the reinforced samples were higher than the unreinforced sample. The Al-20Al2O3-3FLG sample exhibited the highest relative density, 99.25%. According to the hardness measurements, the highest hardness value was 87.28 HV for the Al-20Al2O3-1FLG composite and increased twofold compared to Al6061.

The present study presents an evaluation of the tribological properties of the as-cast Zn-Al-Cu alloy-based hybrid metal matrix composite and also the effect of the weight percent of TiB2. The hybrid composites were fabricated using ultrasonic assisted stir casting with 5 wt.% silicon carbide (SiC) and varying X wt.% (0, 5, 10) of titanium diboride (TiB2). A pin-on-disc type tribometer was used to ascertain the tribological properties like the wear rate and coefficient of friction (COF). The influence of various parameters like the weight percentage of TiB2 particles (0, 5 and 10 %), loads (10, 20 and 30 N) and sliding speeds (0.25, 0.5 and 1 m/s) on the tribological behaviour was determined using the L9 orthogonal array for Taguchi and ANOVA.

In the present study, the arithmetical mean roughness (Ra) values obtained as a result of drilling glass fiber reinforced polymer (GFRP) composite material produced in fiber orientation angles (0º/90º) with different drill bits in a 5-axis CNC controlled vertical machining center, were analyzed. The experimental design was applied with the Taguchi method. The drilling experiments were performed using Minitab 19 software according to the Taguchi L18 orthogonal array. The test results were evaluated based on the signal-to-noise (S/N) ratio. Two different drill bits (HSS and carbide), three different spindle speeds (750, 1000, 1500 rpm) and three different feed rates (0.05, 0.10, 0.15 mm/rev) were selected as the control factors. The effect levels of the control factors on Ra were found by applying analysis of variance (ANOVA). A confidence level of 95.62% was obtained with ANOVA analysis. The lowest Ra value was 1.279 μm at the spindle speed of 1500 rpm and the feed rate of 0.05 mm/rev using a carbide drill bit. The drill bit type was obtained as the parameter with the highest effect with a rate of 61.33%.

A new phenomenological method for composing analytical formulae to describe dynamic systems using the DeSuTra function as a building block is introduced. Based on heuristic considerations, it is possible to write a correct formula with several unknown coefficients. Next, these coefficients are tuned such a way that the result coincides with the experimental data. To illustrate the viability of such a method, a simple but not trivial aerodynamic system was chosen: the autorotation of a rectangular piece of paper that falls in air. Three correction coefficients (diminishers) were introduced to calculate its rotation frequency. Then a simple expression for the Magnus effect and drag force was used. All the obtained formulae were experimentally proved and the coefficients calculated. The conclusions drawn confirm the usefulness of the presented calculation procedure for the design of composites with chaotically distributed reinforcements.

The presence of particles and fibers as reinforcement in a polymer matrix greatly enhances the mechanical properties. Agricultural residues and natural fibers are commonly used nowadays due to the fact that they easily decompose even after a longer period and they are eco-friendly in nature. Fiber that was extracted from stem of Calotropis gigantea was selected as reinforcement in the present investigation. Initially the fiber was treated with a sodium hydroxide solution and CG fiber-epoxy composites were prepared. The properties of alkaline treated CG fiber-reinforced epoxy composites were further improved by the addition of particles such as chitosan, red mud and rice husk. Properties such as the tensile strength, flexural strength, impact toughness, hardness, water absorption, thickness swelling behaviour, specific wear rate and coefficient of friction were evaluated and compared. The XRD pattern of the chemically treated CG fiber-reinforced parrticle-filled epoxy composites was presented in the present study.

In recent years, advancements in development of composite materials can be distinctively observed and taking ecological factors into account, researchers are currently working on the development of natural fibre composites for various applications. The current work concentrates on assessment of the mechanical and wear characteristics of sisal-glass (natural and synthetic) epoxy hybrid graphite filled composites. A comparative characteristic study was performed in the study between synthetic (glass) and natural (sisal) FRP composites and it was found that graphite filled FRP composites exhibit excellent tensile properties, flexural modulus enhanced by 35.2%, the hardness and impact strength were improved with the addition of graphite filler. Statistical analysis was conducted using the design of experiments with the help of ANOVA software. From the tribology tests, it was noticed that the COF and wear loss of the composites with the natural reinforcement are comparatively higher than that of the synthetic fibre. It is evident from ANOVA and regression analysis that the reinforcement has 57.99% influence on the wear rate. Due to increased environmental consequences, natural FRP composites are recommended to be used in as automotive brake friction material and aerospace body parts.

The paper presents a fairly extensive review of the procedures and recommendations for checking the damaged repair area of various composite structures (such as sandwich or honeycomb structures) of airframe elements in military and civil airplanes (especially Boeing and Airbus airplanes and sailplanes). The presented requirements for the inspection and assessment of damage (e.g. delamination in layers or in the honeycomb, internal delamination in the laminate, and damaged fibers) should not exceed the permissible damage limits (PDL). The repair requirements (to ensure the continuing airworthiness of the structure) are largely dependent on the classification of the structure under consideration. In these analyses, a fairly important function is performed by non-destructive methods (such as ultrasonic bond testing or using eddy currents), thus assessing the degree of damage and the ongoing maintenance process.

The paper presents advanced analytical modelling of the linear elasticity and viscoelasticity of thermosets and unidirectional long glass fibre-reinforced thermoset-matrix (UFRT) composites. New non-aging materials fully relaxed after the curing and post-curing processes are considered. Quasi-static long-term isothermal reversible viscoelastic processes under normal condi-tions are modelled. The thermosets are isotropic materials with viscoelastic shear strains and elastic bulk strains, and the fibres are isotropic and elastic. New rheological models for thermosets and UFRT composites, described by the smallest possible number of material constants, are developed. The viscoelastic generic function for shear/quasi-shear stresses is assumed as the Mittag-Leffler fractional exponential function in an integral form. The thermoset is described by two elastic and three viscoelastic parameters. The homogenized UFRT composite is described by five elastic and five viscoelastic parameters. Conjugated/unconjugated standard/inverse constitutive equations of the linear elasticity/elasticity-viscoelasticity governing thermosets and UFRT composites are formulated. The equations are mutually analytically transformable.

Many studies around the world focus on the use of organic and inorganic additions to polymer composites to enhance their mechanical properties. Investigations were conducted to study the mechanical properties of composites with nano-kaolinite weight fractions of 1, 3, 5, 7, and 12% incorporated into an epoxy matrix. Further investigations were carried out on the diffusion of the epoxy nano-kaolinite monomer into the interfibrillar space when polypropylene and Kevlar rope fibre were added. The Kevlar fibre/matrix and polypropylene fibre/matrix interfacial shear strength was evaluated by the single fibre drag-out method. The highest interfacial shear strength was observed at a 5 wt.% nano-kaolinite content. Energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), as well as characterisation by X-ray diffraction (XRD), were performed on all the epoxy/nano-kaolinite, Kevlar specimens.

In this study the mechanical properties of polypropylene (PP) with a small amount of TiO2, after UV-C exposure were preliminarily analyzed. The effectiveness of titanium oxide was evaluated in two alternative applications: TiO2 as the polymer filler and TiO2 as a protective outer coating. The samples were exposed to UV-C rays for 1000 hours. It was found that an addition of 5 wt% TiO2 to PP matrix results in a 60% smaller decrease in Rg after 1000 h of exposure to UV-C than in the case of neat polypropylene. It was also found that the addition of TiO2 to the polypropylene matrix is more effective than TiO2 applied as a coating component. The Rg decrease after exposure is about 35% in this case. The research confirmed that TiO2 submicrometric particles seem to be a very good component in reducing the sustainability of polypropylene to UV radiation.

The study continues the advanced analytical modelling of the linear elasticity and viscoelasticity of thermosets and unidi-rectional glass fibre-reinforced thermoset-matrix (UFRT) composites. The thermosets are isotropic materials with viscoelastic shear strains and elastic bulk strains, and the fibres are isotropic and elastic. The modified homogenization theory for UFRT composites, based on the selected tasks of the linear theory of elasticity, is developed. The modifications include a volumetrically equivalent cylindrical representative volume cell, solutions determined for an isotropic fibre based on the solutions for a mono-tropic (transversely isotropic) fibre, and certain modifications in the third task of the theory of elasticity. The viscoelastic con-stants of the thermoset are derived analytically and validated by fitting of the simulation and experimental shear strains on a logarithmic time scale in the unidirectional tension creep test. The viscoelastic constants of the UFRT composite are derived analytically and validated by fitting of the storage compliances corresponding to the new viscoelastic model and one obtained from the viscoelastic-elastic correspondence principle. The tension creep experiment is performed on the selected structural unsaturated polyester resin. Identification and validation are carried out for that thermoset and the corresponding UFRT com-posite with long E-glass fibres. All the modelling hypotheses are confirmed.

A hydroxyapatite (HA) based biocompatible and bioactive composite is an appropriate choice for bio-implants. This experimental work presents the influence of ZnO and Fe3O4 on the microstructure of HA-ZnO-Fe3O4 composites synthesized by the wet powder metallurgy process. These composites were characterized using SEM, energy-dispersive X-ray spectroscopy (EDS), and XRD. The obtained results showed the effect of the addition of Fe3O4 on the interface formation, which is exhibited by interconnected pores and sintered neck in the micrographs. The observed porosity helps to enhance the required osseointegration for the fixation of implants with human bones.

An evacuation shelter provides simple living facilities made of lightweight materials for repeated use and ensures that the shelters provide a safe and suitable long-term environment. Improving the shelter material in terms of thermal quality in the Malaysian climate is one requirement when evacuating victims to emergency shelters in open areas. The article aims to investigate the effect of using local natural fibers for composite honeycomb skin on the thermal and mechanical performance. The composite skin is a natural fiber processed in a concrete panel to make a honeycomb sandwich. This work introduces a model of natural fiber distribution embedded in a concrete panel, which is subjected to thermal analysis and three-point bending (TPB) to optimize the honeycomb structure. In order to understand the thermal interaction of the panel sheet for an insulating system, the model provides a six-level range of the number of fibers (100, 200, 300, 400, 500 and 600) to analyze the fiber network. The simulation demonstrated that improvement in the insulating panel of about 2.58% could be achieved by using the number of 600 coconut fibers, which is much lower compared to plain concrete. The morphology study successfully demonstrates the understanding of the fiber distribution and thermal absorption by the concrete. Moreover, the mechanical performance is also positively affected by using fiber in the panel, especially sugar cane, which achieved a 47% improvement. This successfully simulated model provides a promising solution to promote local products for shelter material applications.

The paper presents a preliminary study on the effect of an addition of barium sulfate (BaSO4) particles on the mechanical properties of polypropylene (PP) and an evaluation of the effectiveness of this additive in protecting the material against UV rays. Tests were carried on PP samples filled with BaSO4 powder and on samples covered with a protective coating based on BaSO4. Samples of the materials were exposed to UV-C rays for 1000 hours. After exposure, specimens were subjected to static three-point bending tests and hardness examination. Based on the obtained results, it was concluded that BaSO4 reduces the decrease in flexural strength and in hardness caused by exposure to UV-C rays by half in comparison with neat PP. The action of BaSO4 particles as a filler of PP and as a component of a coating applied on the surface of the sample results in similar anti-UV protection of the material. BaSO4 seems to be a commonly available and inexpensive anti-UV protector for plastics.

The shrinking resources of fossil fuels and the growing pollution of the environment have caused people to begin to search for possibilities of reducing energy losses. Vast possibilities in this area lie in industrial transport, called short distance transport, as well as in civil engineering. European Union authorities set limits for the emission of harmful pollutants and energy losses. That is why the laboratories of many research centres conduct research on composite insulating materials taking into account a nanotechnology and air gaps. The paper presents the results of research on steel pipelines used in the transport of hot media, insulated with PUR shaped materials covered with a composite coating with a polymer resin matrix containing an air gap between PUR and the pipe. Such a solution makes it possible to employ the reflective properties of selected materials, which, thanks to reflection of the heat flux, returns it to the source. An air gap with the thickness of 10 mm under the conditions of the conducted research, allows the heat losses of an steel industrial pipeline to be reduced by 7.6%.

This paper is devoted to important issues of determining the strength and predicting the failure processes of composites. These issues enable determination of the limits of safe use of a product and the recognition of when limits are reached. It investigates the distribution function of the composite and its components. The developed model that is presented in this paper enables description of not only the predictable strength of unidirectional composites, but also the character of the failure, taking into account the fiber stress and/or ultimate strain distribution.

The article aims to study the impact of date palm powder (DPP) on the mechanical and thermal characterizations of a high- -density polyethylene (HDPE) matrix. HDPE composites enhanced with ratios varying from 5 to 20 wt.% DPP were produced by means of a twin-screw extruder. The results indicate that incorporating between 5 to 20 wt.% DPP in pure HDPE led to an increase in the tensile strength and Young’s modulus, while the elongation at break decreased. Furthermore, the results of thermal gravimetric analysis (TGA) revealed that incorporating DPP into pure HDPE improved the thermal stability owing to a reduction in the interfaces between DPP and the pure HDPE matrix, resulted in brittle behavior, and enhanced the great crosslinking of pure HDPE.

This paper presents an analysis of the damage process of composite laminates subjected to low-velocity quasi-static indentation (QSI) load. The laminates were prepared using the compression moulding technique. The composites were made from orthotropic layers with E-glass or steel fibres and a polypropylene matrix. The quasi-static indentation tests were carried out at three levels of indentation energy under low-velocity. The experimental results reveal that using steel fibres increases the perforation threshold, which alludes to the importance of the fibre type in delineating damage regions. In contrast, the evolution of the damage and the perforation resistance of glass fibre reinforced laminates is somewhat different. A numerical model based on a finite element program was developed to understand the mechanisms of damage evolution in the laminates. It involves implementing the Matzenmiller-Lubliner-Taylor (MLT) damage model. A comparison between the experimental and numerical results was also made.

This publication describes the effect of shredded (milled) car windows on the structure and mechanical properties of rigid polyurethane (PUR) foam. The multi-stage shredding (crushing + milling) process for car windows provides an effective method for reusing the material as a filler. The proposed method of the mechanical recycling of windshields is energyconsuming, which increases the costs of recycling processes. At the same time, this method is scalable, which allows the processes to be transferred from the laboratory to the industrial scale. The mechanical properties of the foams reinforced with shredded glass were assessed by performing a compression test in accordance with standard PN EN 826. The obtained results demonstrate the effectiveness in increasing the compressive strength for the two-component polyurethane foam with densities of 30, 50 and 70 kg/m3. The addition of milled glass in the amounts of 10, 20, 30% by weight increases the compressive strength of the rigid foams from 10 to even 90%. The filler particles create areas where new pores form, resulting in the reinforced PUR foams having more small pores than the neat PUR foams. The sharp edges of the glass particles act as “cutting blades” for the pores that form, which is manifested by the foil effect on the filler surface.

In this study the distribution of microhardness in a polypropylene microcomposite reinforced with talc microparticles was measured experimentally. The microhardness was measured at different points of the composite material to try to observe the effects of the talc particles and their proportion in the composite on the hardness of the reinforced polymer. Four proportions of talc were used: 5, 40 and 50 wt.%, in addition to virgin polypropylene, which was taken as the reference. Statistical analysis was performed on the distribution of the microhardness in the PP+talc composites to determine the average microhardness and the standard deviation. The obtained results reveal a random distribution of the microhardness of the composite, but in general the presence of talc particles increases the microhardness of the polypropylene.

This article presents an attempt to evaluate the mechanical properties such as the flexural strength and impact strength of polymer concretes based on unsaturated polyester resin reinforced with milled car windscreen waste glass and quartz sand. A set of five samples was prepared with a stable volume content of resin at 30% and varying proportions of milled glass from recycled car windscreens and quartz sand. The materials were tested in static and dynamic (Charpy) bending conditions. Based on the collected data, it was found that the most favorable properties were obtain by the polymer concrete with milled glass, and milled glass and sand (volume ratio 1:1). It is predicted that the developed materials can be successfully used in the production of paving slabs as well as prefabricated garden and road accessories. This would enable the disposal of troublesome waste, which is car windscreens, to produce high-quality products with a long service life.

Metal matrix composites (MMCs) have elevated properties when compared to their parent metals. Aluminium, due to its light weight has a versatile set of applications. In the present work, the 2024 aluminium alloy was chosen as the metal matrix, was melted and stir cast at a temperature of around 900°C along with an addition of a nickel-titanium (Ni-Ti) in powder form as the reinforcement in varying proportions (2, 4, 6, 8% weight fractions). Tests were conducted to analyse the tensile strength, impact strength, elongation and microstructure of the produced specimens. SEM micrographs revealed that the MMCs with 2 and 4 wt.% reinforcement exhibited better dispersion of the reinforcement. The composites having the 4 and 6 wt.% additions of Ni-Ti powder exhibited better ultimate tensile strength when compared to the other specimens, whereas the one with the 8 wt.% addition of Ni-Ti powder revealed better impact strength. Some agglomerations of the Ni-Ti particles were observed on the fractured surface. When evaluating the optimum result using design expert or the design of experiments, it is understood that when the data points are evenly split, either transformation or a higher order model can improve the fit to obtain the optimum result. The yield strength of the metal matrix composite which indicates the ability of the material to withstand permanent deformation varies with respect to the additions of Ni-Ti powder. It occurred that the MMCs with the 4 and 6 wt.% reinforcement produced better results when compared with the 2 and 8 wt.% ones, respectively. The impact strength of the composite containing the 8 wt.% addition exhibited better resistance when compared with the 2, 4 and 6 wt.% reinforced MMCs. It was revealed that the 8 wt.% addition of Ni-Ti powder to the metal matrix resisted fracture due to the applied load. The lower limit for the ultimate tensile strength is 186 MPa and for the upper limit it is 212.14 MPa, which are within the acceptable range; therefore, the optimum results are within the limits.

Alumina toughened zirconia (ATZ) composites with 2.3 vol.% Al2O3(ATZ-B) and 12.3 vol.% Al2O3(ATZ-10) were fabricated. The used starting zirconia powders were prepared as a mixture of powders with different yttria content. The alumina additive was commercially available Al2O3 powder. The specific preparation method and optimized sintering conditions allowed us to achieve ATZ products with exceptional properties. These properties were compared with 3Y-TZP sintered samples prepared from commercial powder (Tosoh). The structural and mechanical properties of the investigated ATZ composites were systematically studied. The microstructures were observed by scanning electron microscopy (SEM) on polished and thermally etched surfaces, then the micrographs were binarized and subjected to stereological analysis. Dense (> 99% of relative density), uniform and pore-free microstructures with homogeneously distributed Al2O3 inclusions without any visible agglomerates were obtained. The Vickers hardness and Young’s modulus were enhanced according to the rule of mixtures for the composites. The mechanical behaviour was especially oriented towards increasing the fracture toughness. The K1C parameter reached the extraordinary value of 12.7 MPa
m1/2 for ATZ-B and 9.8 MPa
m1/2 for ATZ-10. Comparatively, K1C of the 3Y-TZP reference material was 5.1 MPa
m1/2. The mechanisms contributing to the increase in K1C were identified to explain the reason for such a large improvement in the fracture toughness. The investigations were particularly focused on crack propagation analysis. The identified mechanisms include crack path deviation and mixed transgranular-intragranular crack migration (crack bridging), crack propagation through theAl2O3 grains and frequent changes in the fracture propagation directions of a high angle (close to even 90°). Nevertheless, the occurrence of tm (tetragonal to monoclinic) transformation of the ZrO2 phase was considered to be the main toughening factor. Due to the specific method of preparation, leading to an intensification of yttrium diffusion during sintering, the final microstructure revealed very small grains of a tetragonal zirconia phase. These grains exhibited high transformability, which was the main reason for the distinctin crease in fracture toughness.

Aluminium matrix composites (AMC) are mostly preferred for their high specific strength, high ductility, corrosion resistance and creep resistance. Various experimental investigations are conducted in the field of AMCs, which are widely applicable in several fields like aerospace (especially aircraft structures and fittings), marine fittings, automotive industries (connecting rods, pistons, brake rotors, and engine blocks), etc. The current work presents the effect of a tungsten carbide (WC) reinforced Al6061/SiC hybrid composites. In this study, the WC particle (3÷5 μm) content is varied from 0 to 6 wt.% in steps of 2 wt.%, while keeping the SiC particle (63 μm) content of 5 wt.% constant. The stir casting method was used to prepare these composites and the behaviour of the composites was studied to ascertain their mechanical and corrosion properties. From the obtained results, it was observed that the ultimate tensile strength, hardness, and corrosion resistance of the composites are enhanced by increasing the content of WC, whereas the wear loss (microns) decreased as the WC was increased up to 4 wt.%; later it increased drastically at 6 wt.% WC. The corrosion results reveal that the corrosion rate of the composites is lower than that of the monolithic alloy. SEM examination of the tensile fracture surface shows that there is a formation of larger shear lips in the base alloy and the composite with 5 wt.% SiC; however, they are reduced gradually by the additions of WC to the composite. The microstructure of the corroded surfaces reveals that the pit density was reduced for the composite with 6 wt.% WC compared to the other composites.

The fabrication of polymer-based nanocomposites by means of twin extruders is a typical method for manufacturing lightweight and high-strength structures. However, selection of the optimal parameters for this process to study the material characteristics is important. The primary aim of the present study was to ascertain the optimum extruder temperature and nanosilica content in an acrylonitrile-butadiene-styrene matrix composite. The response surface methodology was based on two factors and three levels. The identification of the effect of the parameters on the fatigue behavior of the fabricated composite was comprehensively analyzed. The results were analyzed using scanning electron microscopy (SEM). The obtained results revealed that up to 4% nano-SiO2 improves tensile strength and reduces the impact toughness. On the other hand, an increase in the extrusion temperature yields a higher impact toughness and lower tensile strength. The optimization results showed that 2.5% nanosilica and the extrusion temperature of 225°C result in the maximum tensile strength of 41 MPa, and impact toughness of 30 KJ/m2.The fabrication of polymer-based nanocomposites by means of twin extruders is a typical method for manufacturing lightweight and high-strength structures. However, selection of the optimal parameters for this process to study the material characteristics is important. The primary aim of the present study was to ascertain the optimum extruder temperature and nanosilica content in an acrylonitrile-butadiene-styrene matrix composite. The response surface methodology was based on two factors and three levels. The identification of the effect of the parameters on the fatigue behavior of the fabricated composite was comprehensively analyzed. The results were analyzed using scanning electron microscopy (SEM). The obtained results revealed that up to 4% nano-SiO2 improves tensile strength and reduces the impact toughness. On the other hand, an increase in the extrusion temperature yields a higher impact toughness and lower tensile strength. The optimization results showed that 2.5% nanosilica and the extrusion temperature of 225°C result in the maximum tensile strength of 41 MPa, and impact toughness of 30 KJ/m2.

In this study, the surface morphology of composites, the effect of the particle geometry like the size and shape of the filler materials, their dispersion efficiency and interfaces are analyzed by morphological characterization. According to the tensile tests, it was found that the composites fabricated with CuO exhibit increasing trends of tensile strength in all the experiments compared to that of the composites with TiO2, which is verified by the degree of composite crystallinity determined by the strong interfacial interaction as well as the size, shape and compactness of the filler particles as observed by SEM micrograph analysis using Mountains software. Evaluation of this analysis shows similar amplitude variations in all the PSD curves of the composites and indicate a fatigue-like behavior. The stable isotropic properties in the composite samples with CuO result in a better surface finish, which was also well defined in the analysis of its surface texture and density function. Due to all these positive correlations, a significant rising trend in tensile strength (55.50, 105.53 and 20.40%) was found in every composite modified with CuO in comparison toTiO2. The highest tensile strength of the fabricated composite incorporating the CuO functional filler was found to be 105.530%. Such composites with TiO2 and CuO having a tensile strength of 117.9 and 141.95 N/mm2 respectively, may be used for the interior design of aircraft, watercraft, offices, residences, car and sports accessories and others.

The out-of-autoclave process is being used instead of the autoclave process due to its lower manufacturing costs to obtain products of the same quality. It is seen that in the out-of-autoclave, pre-cure processes like compaction in the vacuum bag, the bagging sequence, vacuum pressure as well as the application time of vacuum are the major factors to produce acceptable quality parts, especially aero structure parts. In this study we will discuss how the bagging sequence, along with a change in the consumable materials, affects the final porosity. The void content for different bagging sequence conditions was analyzed by means of C-scan and microsection analysis on OOA prepreg laminates. It was noted that the bagging sequence and consumable materials may cause the porosity to be as low as ≈ 0.23% to as high as ≈ 4.24%.

In this study, the effect of the addition of K-10 montmorillonite (MMT) nanoparticles on the mechanical and thermal properties of carbon-carbon composites were investigated. The composites were obtained using self-made prepregs with plain and twill 2/2, 600 g/m2 carbon fabric and phenolic-formaldehyde resin. The composites were obtained by the hot pressing technique, followed by carbonization in an inert argon atmosphere. Modified samples of the composites contained 5 wt.% MMT, homogenously dispersed in the ceramic carbon matrix. The mechanical properties, thermal conductivity and thermal capacity of the composites were determined. Raman spectroscopy and Fourier transform infrared spectroscopy were used to investigate the carbon matrix composition and structure. The results show that the addition of MMT nanoparticles increased Young’s modulus by 48%, Kirchoff’s modulus by 80.2%, but did not change the interlaminar shear strength nor the bending strength. The MMT influenced the carbon microstructure, changed the ID/IG Raman ratios, as well as the matrix composition. The addition of MMT also increased the low temperature regime of thermal conductivity and diffusivity of the samples.

The aim of this work is to accurately characterize the thermomechanical behavior of jute-polyester composites. The thermal characteristics and the mechanical properties are determined over a temperature range from ambient to 100°C. The effect of temperature on the tensile breakage of specimens was investigated in order to determine the ability of this composite to maintain its mechanical resistance. It was observed that Young’s modulus and the tensile strength undergo an increase of about 80% when the temperature rises from ambient temperature to 60°C and a decrease for a temperature range from 60°C to 100°C. Numerical simulations, based on FEM analysis, provided results in good agreement with the experimental data in terms of the stress-strain curves. These simulations were achieved using Abaqus explicit finite element code. The increase and decrease in the mechanical properties were attributed to modification of the adhesion forces at the fiber/matrix interface.

The aim of this work was to conduct an experimental investigation of the mechanical behaviour in the three-point bending of fatigue-stressed cross-ply laminated composites. A 3-point static bending study was carried out on two types of laminated composite materials to determine their mechanical characteristics as well as to assess the influence of the test speed and the effect of the stacking sequence on their mechanical behaviour. Different damage modes leading to the rupture of these materials were highlighted to determine their types.

Biocomposites consisting of polylactic acid reinforced with 2 to 8 wt.% walnut shell and pine needle ash fillers were fabricated by the microwave heating technique. The mechanical properties such as tensile strength, flexural strength, impact strength, Vickers hardness, and sliding wear behavior of the produced biocomposites were examined. The tensile strength declined by 11.62% with a reinforcement of 8 wt.% pine needle ash (PNA) in the PLA matrix as compared to the neat PLA matrix. The flexural strength also dropped by 3.09% with the reinforcement of 8 wt.% PNA in the PLA matrix compared to the neat PLA. It was found that the impact energy was enhanced by 77.27 and 66.67% with the reinforcement of 8 wt.% PNA and WN fillers in the PLA matrix, respectively. The Vickers hardness also improved by 14.54 and 10.35% with the reinforcement of 8 wt.% PNA and WN fillers in the PLA matrix, respectively. In addition, the weight loss due to sliding wear was improved by 95.86 and 94.52% with the reinforcement of 8 wt.% WN and PNA fillers in the PLA matrix as compared to the neat PLA matrix, respectively. The drilling forces (thrust force and torque) were additionally recorded during the drilling process of the PNA and WN filled PLA based biocomposites.

The present study aimed to analyze the wear behaviour of composites synthesized by reinforcing Al 4032 with 2, 4, 6 wt.% of coal ash using the stir casting technique. Wear testing was performed on the composites at room temperature in the absence of lubrication using a pin-on-disc tribometer considering the process parameters as wt.% of reinforcement, speed and load. Micro structural characterization using scanning electron microscope (SEM) and energy dispersive X-ray analysis(EDX) was performed on the cast composites to ascertain the existence of the reinforcement along with its distribution in the prepared composites. The Taguchi L16 orthogonal array was utilized to design experiments to study the significance of the process pa-rameters on the wear rate. A mathematical model was developed for the wear rate using response surface methodology (RSM). 6 wt.% reinforcement, at the speed of 100 rpm and 10 N load were the obtained optimized parameters for the mini-mum wear rate. Surface plots as well as contour plots were analyzed to understand the consequence of the process parameters on the wear rate. The analysis of variance (ANOVA) revealed that speed with 76.10 % was the most prominent parameter fol-lowed by load and reinforcement with 11.23 and 9.42% respectively.

In this work, the composite samples required to investigate their thermal properties were fabricated employing the con-ventional hand lay-up technique, followed by a light compression molding process. A fixed weight of plain woven glass fiber and epoxy with four different types of fillers as calcium carbonate (CaCO3), aluminum oxide (Al2O3), magnesium oxide (MgO) and titanium oxide (TiO2) or copper oxide (CuO) of different weights (5, 10 and 15 g) were studied. According to thermal gravimetric analysis (TGA), it was observed that the melting point (Tm) and glass-transition temperature (Tg) are affected by the presence of CuO and TiO2, which indicate the degree of composite crystallinity established by the stronger interfacial in-teraction by the CuO than that of the TiO2 particles and the amorphous region of the chain. These studies were supported by examination of the surface morphology of the composites by means of scanning electron microscopy (SEM).

The present study investigates the influence of pigmental impurities on glass fibre-reinforced polypropylene using model compounds to simulate the behaviour of recyclate-based compositions. Most industrial-quality (containing recyclate) PP com-pounds are black coloured (using carbon black pigment), with an almost unavoidable presence of inorganic white pigment (e.g. titanium dioxide) impurities. There are widespread beliefs in the compounding industry that such impurities have a det-rimental effect on the mechanical properties of glass fibre-reinforced compounds, but up to now no systematic study of this problem from the industrial point of view has been reported. For this purpose, a range of compounds was prepared on a twin-screw compounding line and the properties were evaluated, with special focus on the mechanical properties. The results con-firmed the strong influence of some white pigments, particularly titanium dioxide, and rejected the thesis of the detrimental action of carbon black.

Composites materials have attracted a great deal of interest for use in various fields e.g. the transport industry, construc-tion, sport equipment and even home applications. This is due to the excellent properties of composite materials such as their high strength/stiffness to mass ratio. Nowadays, finite element (FE) modelling allows investigation of the behaviour of compos-ite materials subjected to loading before the production stage. This paper compares the available ways of FE modelling of composite materials: shell, solid shell and solid layered composite modelling in MSC Patran/Nastran software. The aim of this research work was a comparative analysis and determination of the influence of the applied modelling type on the simulation results. Numerous finite element analyses (FEAs) (tensile and bending) of different narrow plate (resembling a slender, beam-like structural member) structure models were performed, i.e. laminated beam and sandwich beam models, with different layups of layers. The obtained numerical results allow the authors to conclude that shell composite finite element modelling can be considered a practically optimal choice due to reduction of the modelling effort and time, as well as due to obtaining consistent simulation results, especially when having only the basic manufacturer’s set of material constants.

The paper presents a part of research aimed at determining the impact of the speed of resin injection under pressure into the mould on the quality of a laminate. In addition, technological defects such as inaccurate material placement, uneven resin injection into the mould, microvoids and microcracks during gelation are taken into account.For this purpose, the velocity and viscosity of the injected resin (via the Hagen-Poiseuille equation) were analysed analytically, and the gelation temperature of the resin was analysed numerically and compared with the experimental results.Strength tests were carried out on samples of two different lengths made using the RTM method. In the specimens cut with a different measuring base, significant scatter was found resulting from the superposition of effects and phenomena (delamination, voids or scale effect) related to the qual-ity of the produced laminate.

Dynamic tests with different load ratios and frequencies provide designers with the necessary information to evaluate the longevity of different structures as well as minimize weight due to a possibly smaller factor of safety. The influence of loading frequency on the fatigue behaviour of an aluminium composite material (ACP) with an aramid honeycomb core was studied. The mechanical behaviour was assessed by three-point static bending tests, followed by cyclic flexural fatigue tests employing the fabricated sandwich samples, with loading frequencies of 5, 7.5 and 10 Hz. The experimental results were presented on a single graph in order to highlight the different behaviours for the adopted frequencies. Indeed, the tests allowed the authors to determine the different cycle number values necessary to achieve resistance losses of 10 and 25%, respectively. The experi-ments were carried out for the same loading level of 80% of the maximum force, which is taken as equal to the elastic limit in order to avoid the field of plastic deformations.

Today, polymeric composites are mostly used in statically loaded rather than dynamic load-bearing parts in machines. Their light weightiness, durability, relatively low prices, flexibility in their use, and fast production features constantly have been opening new ways for their use. In this study, the design, analysis, and experimental verification of a short glass fiber reinforced polyamide + polyphthalamide hybrid polymer machine part functioning under dynamically varying loads and harsh chemical and heated environments is presented. One such machine part is a washing machine drum support to which no composite material had ever been applied successfully before, as known to the authors. The study shows that at least 50% short glass fiber reinforcement, long term polymeric material mechanical properties as well as certain geometric stiffening modifications have been applied for this composite part to function as an equivalent cast aluminum alloy part

Nowadays, many parts of automotive components are made of composites. One application of composites is brake lining material in braking systems. Fly ash is waste from burning coal in the power plant industry. Fly ash was added to a polymer matrix to enhance the wear properties of the composite. The appropriate temperature and pressure for composite fabrication were chosen from the composite which has the highest hardness. The addition of 30 wt.% fly ash to the phenolic resin matrix resulted in the lowest specific abrasion of the composite. Additions of graphite, iron powder and nitrile butadiene rubber increased the specific abrasion of the fly ash/phenolic resin composite. Scanning electron microscope micrographs showed the distribution and agglomeration of the particles in the phenolic resin matrix. The addition of fly ash to the phenolic resin matrix also increased the temperature resistance of the composite. Thermogravimetric analysis shows that the starting temperatures for decomposition of the composite constituents shifted to higher temperatures as the fly ash content increases.

The aim of this study is to assess the possibility of using an innovative two-layer polymer concrete system as a complete outdoor terrace surface. The work is a preliminary technical study. For the purpose of the work, two samples differing in aggregate used were produced. One of them was filled with a mixture of gravel (coarse grain) and sand (fine grain) aggregate, the other was filled only with gravel (coarse grain) aggregate. The assessment methodology was based on simple tests of selected basic functional characteristics, which were load resistance, abrasion resistance, water absorption, and resistance to dirt. The obtained results of the evaluation of the produced materials indicate that the concept of using a two-layer polymer concrete system as an external surface is good - the material shows satisfactory behavior both in terms of static and frictional loading, and in terms of water drainage. Polymer concrete with coarse grained aggregate is visually attractive after application, but also susceptible to dirt, which is difficult to remove by simple methods. Hence, it is are difficult to keep clean and aesthetic. Polymer concrete with aggregate containing a fine fraction is easier to keep clean and aesthetic, but it is not as visually attractive as the concrete filled only with the coarser grained aggregate. The applied additional resin protective coating significantly improves the effectiveness of removing dirt from the surface. However, for a coarse-grained surface, the improvement in cleaning performance is probably insufficient. According to the two-layer concept, polymer concrete is an attractive and real alternative material for outdoor terraces. The potential proposal of a two-layer polymer concrete as a terrace surface requires a number of further development works, mainly in terms of the optimization of aesthetics, cleanability and analysis of the issue of water absorption and water freezing inside the material structure.

Electrical characteristics of iron coated multi-walled carbon nanotubes (MWNTs) along with ferromagnetic properties are very interesting nanomaterial for microwave absorption. In this research work, surface morphology, compositions and microwave absorption properties of polymer containing iron coated MWNTs have been investigated. Iron coated multi-walled carbon nanotubes composite were prepared by two simple steps method. In addition, microstructure and microwave absorption properties under frequency range 8÷13 GHz by means of FESEM, EDX &Vector network analyzer had shown. The maximum reflection loss is observed for Fe-coated MWNTs/polymer sample B is –20.86 dB and –18.13 dB at frequency 8.1 and 10.75 GHz respectively. And the maximum bandwidth window is available for sample C is 3.25 GHz from frequency 8.45 to 11.7 GHz with 3 mm thickness, which can be attributed to synergistic effect of improved impedance matching characteristic and superior microwave attenuation characteristic of the absorber. The reflection properties of the material enhanced with variations in the wt.% of Fe-coated MWNTs and polymer. In this research paper, Fe-coated MWNTs are analyzed as promising microwave absorbing material and combined utilization of dielectric loss and magnetic loss absorbent design shows great design flexibility and diversity in the frequency range 8÷13 GHz.

The present work focuses on determining the fundamental frequencies of skew sandwich plates with face sheets considered to be classical thin plates, which are made of a graphite-epoxy material and an orthotropic core made of glass reinforcedepoxy using different boundary conditions. The fundamental frequencies were obtained using finite elements, which are validated with available literature results. The effects of the skew angle, ratio of the length to total thickness of the sandwich plate, and ratio of the thickness of the core to the face sheet on the fundamental frequency of skew sandwich plates were obtained. In addition, the effect of parameters such as the number of layers in the face sheet, the laminate stacking sequence and the fiber orientation angle on the fundamental frequencies of laminated skew sandwich plates was also ascertained. It was found that the CQUAD8 element yields better results than the CQUAD4 element in the present study. The fundamental frequencies were found to increase with an increasing skew angle. The variation in the fundamental frequency is negligible when there are a large number of layers in the face sheet.

Ultrasmall TiO2 nanotubes (TiO2NTs) of the length ~250±20 nm and diameter ~20 nm are synthesized and TiO2NT reinforced (0.1 wt.%) epoxy composites are fabricated. The reinforcing effects are studied by means of tensile, flexural, and impact tests as per ASTM standards. TEM and XRD characterization techniques are used in this study. It is observed that TiO2NTs greatly enhanced the tensile strength by 85%, elongation by 7%, flexural strength by 55%, and the impact strength by 8%. The mechanical properties of the epoxy nanocomposites indicate that TiO2NTs are efficient fillers to enhance the performance of epoxy composites.

Aircraft composite structures made in autoclave prepreg technology are characterized by low porosity and high strength. Unfortunately, composite structures are susceptible to impact damage. Therefore in order to repair this type of structures, an advantageous method of structure restoration is the use of the two-step bonding method. This method relies on creating a composite patch cured in an autoclave and then bonding it into a previously prepared repair area in the repaired structure, created by removing the damaged layers. Thanks to this approach, the patch is produced in accordance with the production process of the repaired element and has similar properties including low porosity. A critical element of repair is the bonding layer between the patch and repaired structure. Difficulties in obtaining an appropriate consolidation pressure (compression) using a vacuum bag can cause local disbonding of the composite patch as well as porosity in the bonding layer. Porosity reduces the strength properties of the joint, and it also reduces its weather resistance, which may contribute to its gradual degradation. The article focuses on analysis of the influence of compression obtained by a vacuum bag on the porosity and thickness of the bonding layer. A professional line for the production of aircraft composites and a mobile system for composite repairs of aircraft structures were used to produce the samples. The computed tomography method was used to measure the porosity and thickness of the bonding layer.

The present study is aimed at identifying the influence of silicon hollow glass microspheres (SiHGM) on a newly engineered metal matrix composite. Silicon micro balloons of various wt.% (2, 4, 6) are reinforced in to aluminium 4032 to produce a composite using the stir casting technique. The mechanical properties of the composite such as hardness, tensile and compressive strength were measured. The dry sliding wear test was conducted on the produced specimens to measure the wear rate and coefficient of friction. The results revealed that the properties of the composite are better with an increase in the wt. % of reinforcement. The presence of reinforcement in the composites was identified using Energy Dispersive X-Ray analysis (EDX). The grain boundaries and grain refinement for various compositions of reinforcements and worn surfaces were analyzed using Scanning Electron Microscope (SEM) micrographs. The process parameters for the minimum wear rate and coefficient of friction were identified and optimized by using the Taguchi L16 orthogonal array. Analysis of variance (ANOVA) was used to determine the percentage contribution of each process parameter. Multi-response optimization was carried out using Grey relational analysis (GRA) to optimize the process parameters to attain a minimum coefficient of friction and wear rate. The variation in wear rate and coefficient of friction are analyzed with respect to reinforcement (wt.%), speed (rpm) and load (N).

This article presents titanium(IV) oxide nanocrystals in the crystalline form of anatase obtained by hydrothermal synthesis using various shape-controlling agents. Two methods were applied. In the first, diethanolamine (DEA) was used as the shape-controlling agent and titanium(IV) isopropoxide (TTIP) as the TiO2 precursor. In the second method, carbonate ions were responsible for controlling the shape, while potassium titanate nanowires (KTNWs) were the precursor of TiO2. The expected application of the nanocrystals was related to the absorption of visible light. Therefore, the main goal was to modify shape-controlled TiO2 with a narrow band semiconductor providing absorption of light in that range. Based on spectrophotometric analysis, it was found that the TiO2@Fe2O3 composites possess a band gap in the range between 2.21 and 2.30 eV which originates from the Fe2O3 nanoparticles. Moreover, a small amount of Fe3+ ions was incorporated into the TiO2 lattice, as evidenced by the band gap ranging from 2.85 to 2.95 eV.

In the case of polymer composites reinforced with natural fiber woven fabrics, microstructural calculations are extremely difficult to perform due to their characteristic variability, among others their mechanical properties. The aforementioned scientific problem has not been thoroughly investigated, hence the purpose of this work was to assess the possibilities of predicting the properties of a composite reinforced with flax woven fabric by micromechanical calculations using the Mori- -Tanaka and the double inclusion homogenization models. In addition, the second important utilitarian problem that was undertaken in the work was assessment of the impact of the size of the representative volume element (RVE) on the obtained results. The analyses were carried out for composites based on epoxy resin reinforced with flax fabrics: plain, 2x2 twill and 3x1 twill types. Based on the performed calculations, it was found that the obtained results depend on the type of weave in the fabric used, the size of the RVE, the number of yarn bands in the RVE and the appropriately selected homogenization method. Guidelines useful for evaluating the optimal RVE size depending on the type of weave were formulated.

This article presents the conditions and factors influencing the performance and requirements of brake disc materials. The wear resistance of brake discs must be as high as possible since the reliability of brakes is a fundamental factor affecting the safety of the object in motion. The influence of temperature on the materials was also analyzed, and materials were selected for brake disc components. This article is a research and review study. The article describes studies performed on a flat single disc brake. The authors presented the abrasive wear rate for the tested composites (AlSi12/carbon and AlSi12/aluminosilicates) before and after heat treatment (solution heat treatment at 520°C/4 h and aging at 220°C/4 h). Abrasive wear resistance tests were carried out using a TRN S/N 18-324 device from CSM Instruments, combined with the TriboX v.2.96 system according to the description from the US in the ASTM G 99-90 standard.

In this paper, a hybrid procedure is formulated in order to predict the damage of a laminate composed of UD FRP laminae under random loading. This procedure is based on two pillars: a stiffness degradation model (SDM) combined with an energy approach taking into account the effect of load ratio in addition to a system of equations generated by SSDQM (space state differential quadrature method), which we solved with a novel technique. The outputs of SSDQM, previously used for free vibration behavior analysis of composite structures, are used with those of SDM to predict the damage failure of a composite laminate subjected to random loading. The obtained results correlate very well with the experimental ones and an extensive comparison with other models validate the accuracy and convergence characteristics of this hybrid procedure.

The following paper discusses the studies of high-density polyethylene (HDPE) reinforced with glassy carbon (GC) particles. The conducted research focused on the processing properties of the material. Samples were made from extruded HDPE filament reinforced with GC. The granulate for extrusion was made by depositing GC particles on the surface of HDPE granules in ethylene alcohol. The granulate was subsequently extruded in the form of a filament (1.6 mm in diameter). The filament was cut into smaller pieces, which were then prepared and examined using a light microscope. Density measurements and quantitative analysis were performed to examine the amount of glassy carbon in the samples. The measurements showed about a 1% volume of glassy carbon in the reinforced filament. The melt flow index was measured for the HDPE filament and HDPE filament reinforced with GC. The viscosity curves for the neat HDPE and the composite filament were determined. The reinforced HDPE filament was characterized by slightly lower flow parameters; however, the difference between the results was insignificant for material processing. The maximum feed rate of the prepared filament for the FDM 3D printing process was evaluated by mathematical modeling. The results show that both the prepared materials have a similar printing capability as commonly used PLA, only the composite filament should have a 1.4% lower feed rate than the neat HDPE.

In 2019, the first basalt fiber production line was created in Poland. The fiber is produced in a continuous process, according to the technology developed by Polski Bazalt S.A. In order to assess the microstructure of the manufactured product, a number of tests were carried out, according to previously developed procedures. The presented results relate to the study of the basalt fiber microstructure using light microscopy, electron microscopy and atomic forces. The research was aimed at characterizing the fibers, but also developing research procedures that allow assessment of the basic fiber parameters under post-production conditions. The research was conducted in the field of quantitative and qualitative assessment of the basalt fiber microstructure, its diameter, and the size distribution of this value. In addition, attempts were made to assess the thickness of the sizing (as an impregnation layer) on the fibers obtained employing different parameters of the drawing process and various types of impregnation. Based on the obtained results, measurement and research procedures were implemented in the quality control system of the Polski Bazalt company. Tests carried out as part of these procedures confirm the repeatability in terms of the quality and diameter of the produced fiber.

Glass-epoxy composites are increasingly being used in several industrial applications, viz. automobile, marine, aerospace, electrical and electronics components, especially in tribological components, viz. bearings, impellers, cams, driving wheels, bolts, nuts, seals, bushes and gears, which are used extensively in machinery because their lower weight, exceptional strength, resistance to corrosion capabilities, and cost effectiveness. The work focuses on optimization of the process parameters of the dry sliding wear test, viz. the applied load, disc rotation speed, weight percentage (wt.%) of the Halloysite nanotube (HNT) filler, time as well as the track diameter to minimize the wear rate of the glass fabric reinforced epoxy composite against EN-32 steel. In this research, the specimens are fabricated in accordance with the ASTM G-99 standard and the experiment is carried out with various combinations of parameters using a pin-on-disc tribometer, while keeping the time and track diameter constant. To proceed further, trial runs are conducted using MINITAB 19 software to optimize the process parameters for minimum wear by developing Taguchi’s design of experiments (DOE) based on the L45 orthogonal array (OA), and subsequent analysis of the signal-to-noise (S/N) ratio. The results of the optimization clearly indicate that the wt.% of HNT is the most significant parameter that has a significant effect on minimizing the applied load, speed and sliding wear rate. In overview, the experiment results showed that the combined parameters influenced the wear. In addition, scanning electron microscopy (SEM) is performed to study the surface morphologies of the worn specimens and determine the wear mechanism in accordance with the test results. The wear mechanism clearly indicates that there is a larger amount of matrix debris, fiber breakage and fiber-matrix debonding in the neat composites as compared to the HNT filled glass-epoxy composites since a distinct pattern of micro coring and segregation of the filler along the peripheries of the glass fiber-epoxy interstitial sites, leading to strong bonding between the fibers and matrix are observed in the HNT filled composites. The strong bonding thus resists the wear to a certain extent, and the wear debris is relatively less in the HNT filled composites as compared to the neat composites.

The article presents the basics of the production and the results of tribological tests of a composite with an epoxy resin matrix with increased elasticity (Havel LGH 288) containing basalt particles (BP) in the amount of 20, 30 and 40 wt.% as the reinforcing phase, for friction elements of technical means of transport. Comparative tests were performed on a T-01 tribological tester at ambient temperature with pressure p = 5 MPa and relative speed v = 1 m/s, friction distance s = 1000 m. The tester reproduces the brake pad/disc contact. As a result of the tests, it was found that the developed composite material can rubbing against GJL-250 cast iron used for brake discs. The coefficient of friction in the contact stabilizes after runningin of the contact regardless of the particle content (μ = 0.5). The wear of the composite brake pad decreases, and the wear of the cast iron disc increases along with the content of basalt particles. The reason for such tribological properties is the high hardness of the basalt. The basalt particles cutting the cast iron intensify its wear. Their surface after running-in increases the actual contact area, which reduces the coefficient of friction. The matrix wear debris is deposited on the surfaces of the basalt particles. The heat generated by friction causes a local temperature increase on the basalt particles coated with wear debris, which results in a decrease in the coefficient of friction to 0.5, regardless of the BP content.

The method of fabricating metal matrix composites plays a crucial role in obtaining dense materials characterized by high wear resistance. The present work describes an attempt to produce NiAl/CrB2 composites using the next-generation spark plasma sintering (SPS) method, i.e. upgraded field assisted sintering technology (U-FAST) technique. Microstructure characterization was performed by means of scanning (SEM) and transmission (TEM) electron microscopy. The SEM microstructure investigations of the NiAl model material proved practically full densification of the material sintered at 1200°C and 1300°C, even if remnants of surplus nickel were observed at the boundaries of rounded NiAl grains. The NiAl/CrB2 composites, besides fused NiAl and CrB2 grains, showed the presence of a raised level of nickel also at the grain boundaries. The TEM microstructure observations helped to establish that even if the grain boundaries were pinned by nickel-rich precipitates, some increase in grain growth took place, as evidenced by the fact that strings of smaller precipitates were also visible outside the matrix grain boundaries. All these microstructure investigations indicate that the newly elaborated U-FAST technique is evidently capable of producing compacts free of porosity at lower temperatures and during a shorter time than solid hot pressing or vacuum sintering in a semi-liquid state.

Composites based on tetragonal zirconia polycrystals modified with corundum inclusions ATZ (alumina toughened zirconia), are one of the basic and more commonly used ceramic structural materials. They are used especially willingly as parts of devices and machinery working in both dry and wet wear conditions in the presence of hard abrasive particles intensifying wear processes. The mechanical properties of such composites, strength and fracture toughness mainly, strongly depend on their chemical and phase compositions as well as microstructure. The aim of the present work was to investigate an innovative type of ATZ material composed of a mixture of two ZrO2 powders with different chemical composition and a small addition (2.3 vol.%) of nanometric corundum powder. The proper composite materials additionally contained 10 or 20 vol.% commercially available corundum particles. Tests were carried out on the mentioned materials for abrasive wear susceptibility according to the ASTM Dry Sand Test and ASTM Miller Test, using silicon carbide particles as the abrasive medium. As a reference materials, typical TZP (tetragonal zirconia polycrystals) material prepared using commercial powder and ZTA (zirconia toughened alumina) material containing 5 vol.% zirconia dispersed in an alumina matrix were used. The obtained results allowed the usability of the individual composite materials to be verified under various operating conditions.

The applications of silicon carbide-based composites at extremely high temperatures and under high partial pressure of water vapor require some modifications of the silicon carbide structure and microstructure in order to increase the reliability of the composite component. One of the methods of such modification could be to introduce phases containing yttria or chromia compounds into the composite microstructure. The presented paper reports the results of investigations on the SHS of silicon carbide powders enriched with yttrium or chromium precursors. It was experimentally proven that it is possible by the means of the SHS technique to obtain powders containing only silicon carbide and dispersions of yttrium silicate or yttrium silicide. Such powders were consequently compacted by hot-pressing or the U-FAST technique. The level of densification and the phase compositions of the materials were characterized. It was found that the sintering conditions determine the phase compositions of the sintered samples. Consolidation using the hot-pressing technique leads to the decomposition of silicon carbide and reduction of the remaining starting phases. As an effect, free graphite and carbide phases (YC2 or Cr3C2) appear in the sintered samples. Applying the U-FAST technique and short sintering times lasting a few minutes allows some yttium-silicon phases from the SiC-Y system (oxide, carbide, silicide) to be preserved in the sintered material. In the SiC-Cr system after U-FAST consolidation the CrSi2 silicide phase was preserved, which is not desirable in the final material because of its relatively low melting point of 1470 °C.

This paper was written and formulated based on the micromechanical analysis of unidirectional glass fiber reinforced epoxy composite lamina. To simplify the calculations and achieve acceptable results, a few assumptions like idealized packing, the representative volume element (RVE), uniform strain boundary condition, statistically homogeneous unidirectional fiber reinforced composites, etc. are taken into consideration. Translational symmetric transformation was applied and established mathematical models are presented to obtain the values of the effective material properties by means of the simple strength of materials approach so that they can be compared with the semi-empirical model. In addition, a parametric study was carried out to verify the dependency of the fiber and matrix on the overall effective material properties. This will ultimately help to develop the required glass fiber reinforced epoxy composites for their specific applications.

The research concerns an E-glass/vinyl-ester composite reinforced with a balanced orthogonal stitched fabric. According to the EN ISO 14129 standard, the in-plane shear modulus and in-plane shear strength for this composite type are identified from a ±45o off-axis tension test at the crosshead displacement rate of 2 mm/min. The study presents the results of experimental quasi-static ±45o off-axis tension tests in a small shear strain range, aimed at demonstrating that the high nonlinearity of the shear stress-shear strain curve is caused by viscoelastic flow of the resin at low levels of shear stress and by viscoelastic flow and plastic micro cracks of the resin at high levels of shear stress. The tests were conducted applying four quasi-static displacement rates. It was shown that the shear stress-strain curve course and the shear strength value strongly depend on the crosshead displacement rate. To confirm the nonlinearity explanation, a classic short-term (1 hour) in-plane shear creep test was carried out on ±45o off-axis specimens subjected to in-plane shear stress equal to 67% of the average in-plane shear strength calculated according to the EN ISO 14129 standard. The ply sequence blocking viscoelastic flow and plastic micro cracks of the resin was recommended.

Laminated composites were produced by reactive bonding using CuAl10Fe3Mn2 bronze and titanium foils with thicknesses of 0.6 and 0.1 mm, respectively. To obtain the composite sample five foils of bronze and four of titanium were used. During fabrication, the titanium layers reacted completely and formed intermetallics (Ti2Cu, TiCuAl and TiCu2Al). In order to investigate the compressive behavior of the laminated CuAl10Fe3Mn2-intermetallic composites, isothermal compression tests were conducted at the temperatures of 20, 600 and 800°C with two different strain rates of 1·10−3 s−1 and 2.9·10−3 s−1. The thickness of all the specimens was reduced by 50%. During the compression tests delamination of the layers of the composites was not observed. With an increase in the investigation temperature the yield strength of the composites decreased significantly. The results showed that the deformation temperature and the strain rate were equally responsible for the evolution of deformation during isothermal compression. The most favorable compressive deformation conditions necessary to shape the laminated CuAl10Fe3Mn2-intermetallic phases composites without damaging their layers were determined experimentally.

The aim of the study was to verify the possibility of reproducing a steel, welded gear body element, using an epoxy-carbon composite, as an adaptation project. The content includes a description of the design and manufacturing process along with an indication of the problems occurring at various stages. The design procedure included product optimization, mold design, and composite structure design. The molded element was to be a composite monolithic structure and was intended for vibroacoustic studies. The wall thickness of the element was to be 6÷10 mm. Pre-impregnated fabric (so-called prepreg) with an areal mass of 240 g/m2 (outer layers) and 800 g/m2 (structural layers) was used as the material. The matrix was epoxy resin. The technological procedure included producing the mold and molding the product using the produced mold. The mold was made by milling with a 5-axis milling center (CNC), based on a block assembled of epoxy panels. The molding of the product was started by manually lining the mold with a layup of prepregs. During laying, consolidation was carried out several times using a vacuum bag. A full vacuum packet (vacuum foils, breather, delamination fabric) was applied to the layup. The preformed layup was cured in an autoclave at 120°C, at the pressure of 4 bar and a set −1 bar vacuum inside the packet. The total process time was 4 hours. It was found that the obtained product very accurately reproduces the steel housing and meets the assumptions of the comparative element for vibroacoustic testing. The use of the composite allowed the weight of the element compared to the original to be reduced by over 80% without taking into account the weight of additional steel elements necessary for installation and by over 60% including the weight of those elements. The performed procedures and their effect confirm that polymer matrix composite materials are very well suited for reproducing products and creating prototypes.

The newly developed self-heating based vibrothermography method is a non-destructive testing method applicable to polymeric and polymer-based composite structures, which is based on the self-heating effect used as thermal excitation of a structure during testing. The mechanical excitation with multiple resonant frequencies causes viscoelastic energy dissipation in the whole structure, which allows the observation of eventual flaws and damage in the form of differences in the surface temperature distribution observed by an infrared camera. The effectiveness of damage detectability depends on the visibility of thermal signatures of potential flaws and damage, which is often masked by measurement noise and artefacts in thermograms. Therefore, it is suitable to apply post-processing procedures that allow the enhancement of damage detectability. The developed set of tools for thermogram post-processing covers primary methods based on statistical features, and more advanced ones like methods based on derivatives, wavelet transform as well as post-processing methods dedicated for thermogram enhancement such as thermographic signal reconstruction, partial least squares regression or principal component thermography. These methods were implemented in the form of an integrated GUI-based benchmark based on Matlab routines, dedicated to the post-processing of thermographic data acquired using self-heating vibrothermography.

The article discusses the results of research on the structure and mechanical properties of polypropylene composites with glass fiber. The samples for the examinations were made using a Krauss-Maffei (KM65 – 160C1) screw injection molding machine. The investigations encompassed composites with a polypropylene matrix which contained 30 and 50% glass fiber (GF). Part of the material was processed by heat treatment in the form of annealing. The crystal structure of the samples was analyzed on a wide-angle X-ray diffractometer - Seifert 3003 T-T. In most of the obtained diffraction patterns a few strong diffraction reflexes can be seen. They were identified as reflections derived from polypropylene polymorphs: α (monoclinic), β (hexagonal) and from the smectic phase of polypropylene. Dynamic mechanical analysis (DMA) tests were performed on a DMA 242 Netzsch instrument under the mode of a 3-point bending clamp with an oscillatory frequency of 3.0 Hz. The transition to the glassy state is the most evident for polypropylene. In the case of polypropylene composites, the transition to the glassy state is less evident. The largest tendency of the storage modulus value as a function of temperature to decrease was noted for polypropylene and the smallest for the polypropylene composite with a 50% glass fiber content. Higher values of storage modulus E′ were noted after annealing. For all the samples, glass transition temperature Tg decreases after annealing. Investigations of the mechanical properties of the studied composites were also performed: tensile strength testing, Young's modulus, hardness and impact test. In each case the addition of glass fiber caused an increase in mechanical properties. Moreover, it can be noted that the values of the mechanical properties of PP/GF composites after annealing are higher than those of PP/GF composites before annealing. Both the Vicat softening temperature as well as heat deflection temperature are higher for the samples after annealing. SEM micrographs show the mechanism of breakage of the glass fibers and damage of the matrix material. During observation of the fractures, no significant fiber pullout from the polymer matrix was noted. This demonstrates the good adhesion of the glass fiber to the matrix.

The following paper presents the results of investigations on the microstructure and mechanical properties of sintered composites in the zirconia-alumina system, fabricated by various sintering techniques. The investigations were performed for a particulate composite consisting of two continuous ceramic phases – zirconia (TZP) and alumina (α-Al₂O₃), 50 vol.% each. Two different methods were used to produce the samples: pressureless sintering and the U-FAST technique. The microstructure of the obtained sintered composite samples was evaluated using a scanning electron microscope. In addition, the density of the sintered bodies, their hardness and fracture toughness were investigated to evaluate the mechanical properties. Based on the obtained results of the investigations, the influence of the sintering technique on the microstructure and mechanical properties of the sintered composites was determined.

The paper presents the results of mechanical and tribological tests conducted on the surface of Al-Si-Cu/SiCp composite reinforced with SiC particles and modified by friction stir processing (FSP) with different parameters. Changes in the distribution of the reinforcement particles on the modified surface of the composite were calculated and analyzed using a new analytical RVE theory with Eisenstein-Rayleigh-Mityushev sums (ERM-sum) (see the definitions below), and PointSel software. The Vickers hardness test with a 1 N load and the ball-on-disc method were used to test the material properties. A high degree of homogenization of the tested material was observed as a result of its modification, as evidenced by an approximately 4-fold reduction in the size of representative volume element (RVE) cells. The size of the RVE cell decreased almost four times for the material after modification, which indicates the high level of homogenization of the tested material. Moreover, we observed a reduction by order of magnitude of the anisotropy coefficient of the distribution of the reinforcing phase particles after the modification process. A 30% increase in the Vickers microhardness of the representative areas was obtained for the modified composites. After the FSP modification process the friction coefficient increases by 40%, and almost 25% decrease in the specific wear rate is observed. Both effects are attributed to the achieved homogenization of particle distribution and reduction of particle size up to 38%.

In this paper, the structure of NiAl-15wt.%CrB2, NiAl-15wt.%ZrB2 and NiAl-15wt.%TiB2 composite compact materials was studied using SEM. The composites were obtained by sintering in vacuum. The phase composition was studied by XRD analysis. The effect of the diboride additives on the NiAl hardness was studied. It is shown that the initial intermetallic had a hardness of 288 HV20. At the same time, the hardness value for the NiAl-15wt.% ZrB2 composite is 349 HV20, for NiAl-15wt.%TiB2 it is 392 HV20 and for the NiAl-15wt.%CrB2 composite material it is 468 HV20.

Y-α-SiAlON and its composites containing 10 and 20 wt.% titanium diboride (TiB2) were prepared using spark plasma sintering (SPS) at 1750°C for 10 minutes under 50 MPa. Although, the pure Y-α-SiAlON was > 97% dense, the increased TiB2 content resulted in a slight reduction in the relative density of the composites (~2.6% max. at 20 wt.% TiB2). In the presence of TiB2 particulates, the impediment of grain boundary mass transport within the matrix grains might be responsible for such a reduced densification. The addition of TiB2 resulted in a reduced Vickers hardness (HV1), however, the indentation fracture toughness (KIC) of Y-α-SiAlON increased upon an addition of TiB2 up to 20 wt.%. While the HV1 of the 20 wt.% TiB2/ Y-α-SiAlON composite was ~30% lower, the same composite offered around a 28% higher KIC compared to pure Y-α-SiAlON. Unlubricated, reciprocating ball-on-disc experiments up to 500°C in ambient air indicated better wear resistance of the composites compared to pure Y-α-SiAlON up to a 90 N normal load.

Cyclic bending fatigue tests were conducted on randomly oriented short multidirectional glass fiber-reinforced polyester matrices. Standard test specimens were manufactured in rectangles with a volume fraction of 40% glass fibers. The experimental fatigue life results were fitted using S-N curves, which are based on power function equations. S-N curves, which are characterized by important and significant scatter over the lifetime, were correlated using the two-parameter Weibull distribution function to determine the probability of failure and to plot the S-N curves at different reliability levels. These curves are of considerable design value in practical applications of composite materials and predict the sample response at the time of service depending on the degree of reliability.

The use of natural materials to produce various types of products is becoming increasingly more popular, which also applies to composite products. The advantages of such products are not always high strength indicators, but above all their ecological character. In this respect, the best solution is to choose natural raw materials for both the reinforcement and the matrix of the composite. New possibilities of using biocomposites are increasingly being sought. A promising direction for the development of such composites is medical, construction, automotive, single-use products, or even recreational products. The paper presents the functional features of biocomposites made on the basis of various materials from renewable sources. Determining the sound absorption coefficient for thin, rigid composite plates, the possibilities of using wood flakes, sawdust, cork, paper, straw, feather calamus and flax fibers as reinforcement in sound-absorbing composites were evaluated and compared. The results of the research showed differences in the level of sound absorption, depending both on the type of reinforcement material and the frequency range of the sound.

The paper presents the attempt to assess the failure progress of a stitched carbon fiber reinforced plastic (CFRP) laminate by means of simple analysis of the failure energy after static bending tests. A laminate reinforced with a carbon twill weave (2/2) fabric, areal mass of 200 g/m2 in the form of 10 layer preforms was used for the tests. Some of the preforms were machine-stitched with a Kevlar50 thread in lines with a 4 mm stitch length and 5 mm stitch spacing. The matrix of the composites was epoxy resin and the panels were molded by RTM. Curing took place at room temperature for three days. A fiber volume fraction of 50.5÷51.5% was obtained. Static bending tests were carried out on samples of the manufactured materials. The obtained bending curves were subjected to a simple analysis of failure energy. It consisted in determining the energy corresponding to individual stages of the material destruction progress (i.e. the areas under the bending curve) as well as direct and comparative assessment of the determined values. It was found that the applied methodology of simple analysis of the failure process energy allows effective analysis of the failure progress of materials. The total failure energy obtained by the tested laminates in the main directions is: for unstitched about 8% higher than for stitched loaded in the direction along the stitch lines and about 15% higher than for stitched loaded transversely to the stitch lines. This means that less energy is needed to destroy a stitched laminate than to destroy an unstitched one. However, a stitched laminate exhibits a higher value of failure development energy at a later stage of the failure process, which translates into its greater residual load capacity compared to the unstitched one. It was also found that the DI factor (defined as the ratio of energy used to develop the failure process to the energy used to initiate the failure process) is higher for the stitched laminate than for the unstitched one. This trend applies to all the main load directions. This means that the stitched laminate is less fragile than the unstitched one. Analysis of the obtained results indicates that the stitched CFRP laminate is a material with a safer course of destruction than a corresponding unstitched one.

This paper deals with multi-layered FRP composite beams subjected to the three-point bending test. The study is focused on the flexural performance of rectangular composite beams made of glass or carbon fibre-reinforced laminates (GFRP and CFRP). Depending on the fibre orientation, various laminate systems were analysed with the main focus on [08]T and [908]T layups. Tests on three beams with different length-to-thickness ratios included a three-point short beam shear test (SBS), assuming a relatively short beam is in relation to its thickness, which maximized the induced shear stresses. Additionally, two variants of boundary conditions were discussed with layers oriented parallel and perpendicular to the loading plane. Geometrically nonlinear analysis aimed to verify the load-midspan deflection curves for various fibre-reinforced composite beams was performed. The presented initial results concern comparative numerical analysis performed by the finite element method (FEM), which is found to be crucial before further experimental research.

The exponential increase in the potential applications of graphene has forced its inclusion in composites. Presently, composites containing graphene have been manufactured by many conventional processes. Since 3D printing (additive manufacturing) offers a wide range of advantages for manufacturing, researchers from the composite industry are now adopting novel techniques to manufacture graphene based composites via additive manufacturing. When selecting materials for composites, polymers stand out as the top choice for manufacturers because polymers require a low temperature to mold their shape and they are easy to handle when compared to ceramics and metals. Hence, substantial focus of the composite industry is now shifting towards manufacturing graphene based polymer matrix composites. In this regard, this paper provides a brief review of the 3D printing (additive manufacturing) processes which to date have been adopted to manufacture ‘graphene based polymer matrix composites’. The promising physical properties of graphene based polymer matrix composites and the future prospects of functionalizing graphene in polymer based composites is also highlighted.

The work investigated the influence of the share of metallic components on the microstructure and selected properties of Al2O3-Cu-Mo composites. Commercial powders were used to produce the composite samples. The composites were obtained by the slip casting method. Three series of composites with a different volumetric composition of metals in the total content of the metallic phase were obtained: Series I - contained 7.5 vol.% Cu - 7.5 vol.% Mo, Series II - contained 10 vol.% Mo - 5 vol.% Cu and Series III - contained 12 vol.% Mo - 3 vol.% Cu. All the series contained 15 vol.% metal particles with respect to the total solid phases. Rheological analysis showed that the slurries used to make the composites were shear thinning fluids. The X-ray analysis showed that regardless of the volume content of copper in the suspensions used to form the composite, all the composites after sintering were characterized by the presence of three phases: Al2O3, Cu and Mo. It was found that the microstructure in all the series is characterized by homogeneous distribution of the metal particles. All the samples were characterized by high porosity, which resulted in their low relative density. The volume fractions of molybdenum and copper in the composite slightly do affect the hardness and fracture toughness of the composite. The obtained hardness results indicate that increasing the molybdenum content in the composites causes an insignificant increase in the hardness of the samples.

The paper presents the problems in selecting the fiber shape in numerical strength analysis for wood-polymer composites. For this purpose numerical analysis of the uniaxial tensile test for the wood-polymer composite sample was performed. Variable geometry of the fiber model was used. The fiber orientation data were obtained using Autodesk Moldflow Insight 2016 software. Micromechanical calculations based on homogenization methods were performed using Digimat FE commercial code. The results of the numerical simulations were compared with the experiment ones. To manufacture the WP composite, Moplen HP 648T polypropylene (PP) from Basell Orlen Polyolefins was used as the polymer matrix. As the filler 10 vol.% Lignocel C120 wood fiber manufactured by JRS - J. RETTENMAIER & Söhne Company was used. Adhesion promoter P613 by Dupont was used as well. A Dr Boy 55E injection molding machine was used to produce the test specimens. It was noted that the selection of the fiber shape has a significant impact on the consistency of the obtained results and consequently on compliance with the experiment ones. Fiber location calculations were performed for each geometry type available in the Digimat software. The most consistent results for numerical homogenization (Digimat FE) are associated with the choice of a curved cylinder shape of fiber. This may be due to the greatest convergence of the orientation tensor value received from the numerical simulation of the injection molding process during its transformations to the representative volume element model. In addition, this result may be due to the fact that the curved cylinder type of geometry is characterized by the most variable shape due to the degree of curvature. This reflects the real, non-standard problems to determine the shape of the wood fiber in the polymer matrix.

The paper presents an assessment of the effect of fiber orientation on the strength properties of products made from wood-polymer composites by the injection molding process based on micromechanical analysis. For this purpose numerical analysis was carried out for the product model with geometry of the sample intended for the uniaxial tensile test. To determine the actual fiber orientation after the manufacturing process, the orientation tensor values were calculated using Autodesk Moldflow Insight 2016 software. The micromechanical calculations were performed using Digimat FE commercial code. The results (stress-strain characteristics) of the numerical simulations taking into account the calculated fiber orientation tensor were compared to the experiment. To produce the wood-polymer composite, the polypropylene polymer matrix was Moplen HP 648T. As the filler Lignocel C120 wood fibers made by Rettenmeier & Sohns company were applied. A composite with a 10 vol.% content of wood fibers in the polymer was manufactured in the extrusion process by means of a Zamak EHP 25 extruder. For specimen manufacturing a Dr. Boy 55E injection molding machine equipped with a two cavity injection mold was used. Before the numerical simulations the uniaxial tensile test was performed using a Zwick Roell Z030 testing machine. The specimens were tested at the speed of 50 mm/min according to the PN-EN ISO 527 standard. The obtained stress-strain characteristics were used as a verification criterion for further numerical analysis. Moreover, the mechanical properties of the same composite products were predicted for hypothetical fiber orientation types. It was noted that the selection of fiber orientation has a significant impact on the quality of the obtained results compared to the experiment.

In this article the characteristics of the macrostructure, microstructure (LM, SEM) and selected properties of magnesium matrix composites reinforced with carbon open-celled foam with a porosity of 10 ppi, obtained by two casting techniques - gravity casting and pressure infiltration, were presented. The open porosity and hardness of the composites were determined. Tribological examinations in dry friction conditions were performed by the pin-on-disc method, and the coefficient of friction, weight loss of the sample as well as the cast iron countersample were determined, and the wear trace was characterized. Observations of the examined material surfaces after friction tests were conducted by SEM. In comparison to the gravity cast composite, a lower porosity, higher hardness and finer magnesium matrix size were found for the pressure infiltrated composite. The impact of the casting technique also concerned the tribological properties. Both the composites exhibited a lower coefficient of friction in comparison to pure magnesium, but for the pressure infiltrated composite the coefficient of friction, weight loss of the sample and countersample, as well as the depth of the wear trace were the lowest. Moreover, after the friction tests, different effects were observed on the surfaces. In the gravity cast composite the carbon component cracked and separated from the matrix, in contrast to the pressure infiltrated composite where uniform wear was observed while maintaining continuous bonding with the matrix, which explains the differences in the tribological properties.

Titanium dioxide (TiO2) thin films obtained on quartz glass and fly ash cenospheres were studied. Titanium(IV) butoxide (Ti(OBu)4), diethanoloamine (DEA), ethanol and deionized water were used as the starting materials. A layer of TiO2 nanoparticles was coated on the surface of the substrates using the sol-gel method. The thickness of the TiO2 coatings and the influence of the annealing temperature on the formation of TiO2 crystallites were studied. The dried gels were treated for 90 min in the temperature range of 400÷640°C to obtain crystallized anatase and rutile. Additional nanopowder TiO2 samples were prepared and their crystallinity was determined using X-ray diffraction (XRD). It was successfully shown that the anatase crystalline phase is formed when the TiO2 gel is heated to 480°C, while the rutile phase is obtained at 640°C. Changes in film thickness were studied using an atomic force microscope (AFM). The profound effect of gel viscosity on the thickness of the film was noticed. UV-Vis absorption spectroscopy, performed on the sample treated at 480°C (containing anatase phase only), showed strong ultraviolet light absorption below 400 nm. The estimated band-gap value was 3.2 eV. Transmission scanning microscopy (TEM) examination of the powders revealed agglomerated nanoparticles. A uniform, continuous layer on the surface of the treated microspheres was observed under a scanning electron microscope (SEM). The study shows that the annealing temperature has a profound effect on the phase composition and crystallite size of the sol-gel synthesized TiO2 nanopowders.

Polyurea coatings are obtained by hydrodynamic spraying by means of high-pressure, spray-coatingequipment. A chemical reaction between the isocyanate and amine components occurs in the time of approximately 6 seconds, which enables use of the coated object almost immediately after coating application. Polyurea coating modification results in changes in their properties and a cost reduction. In this work modifiers such as expanded graphite, talc and chalk, which are inexpensive, easily commercially obtainable fillers were employed. The curing degree was measured by FT-IR spectroscopy, thermal stability by thermogravimetric analysis (TG) and phase transition temperatures by differential scanning calorimetry (DSC). For the systems stored under different conditions, the tensile strength and Shore hardness in the D scale were also measured. SEM/EDS analysis was performed to assess the dispersion of the modifiers in the polyurea coatings. To determine the hydrophobic-hydrophilic character, contact angle analyses were performed. The addition of the fillers improves some of the parameters, e.g. the thermal stability and mechanical properties.

Microsilica is widely used as a reinforcing filler due to its high commercial availability and low price, which plays a significant role in reducing production costs. It fills the empty volumes of the material and decreases the porosity, which in turn improves the mechanical properties of composites. Polyurea coatings modified with microsilica and aerosil were prepared using a spray-coating machine. The materials were characterised in terms of thermal stability (thermogravimetric analysis -TGA, differential scanning calorimetry - DSC), mechanical properties (tensile strength, Shore D scale hardness), and hydrophilic-hydrophobic properties. To confirm the structure of the obtained materials, FT-IR spectroscopy was used. SEM analysis was performed to assess the dispersion of the modifiers in the polyurea coatings. The physicochemical properties of the obtained compositions were measured after ageing the samples under different conditions, including storing at room temperature, curing for 5 and 14 days at 80°C and weathering for 500 h with UV irradiation in a weathering station. The collected results show that the addition of microsilica improves not only the mechanical properties, but also the thermal stability of the obtained composites.

The paper presents the results of research on a composite coating with a polymer resin matrix containing glassy carbon microparticles as the modifying phase acting as a solid lubricant for piston aircraft engines. Comparative tests were carried out on a T-11 tribological tester at the temperature of 80°C, pressure of p = 8 MPa and relative velocity v = 0.55 m/s of a cam/push rod contact coated with a developed coating (RGC) and a cam/push rod contact coated with a reference coating (RC). 2 mg of AeroShell 100 oil were added to the contact for 10 hours of rubbing. This lubrication simulates the operating conditions of the combustion engine components after lubrication loss. As a result of the tests, it was found that the developed coating can work 10 hours after the lubrication disappears because the coating is porous and absorbs the oil during heating up to the engine\'s operating temperature. The oil sorption is indicated by the increase in the mass of the sample with the coating. Thanks to the coating material anchored in the roughness valleys of the push rod surface soaked with oil, the coefficient of friction, despite evaporation of the volatile parts of the oil, does not exceed μ = 0.1, which prevents seizure of the contact. The contact with the reference coating seized after 8.5 hours of sliding. The tests of the developed coating on the engine dynamometer as well as in the aircraft confirmed the usefulness of the developed coating.

The tribological properties of composite materials reinforced with titanium diboride were investigated. Abrasion resistance tests were carried out at room temperature in a ball-on-disc system. Balls with a diameter of 3.14 mm were used as the counter-samples. The effect of the TiB₂ content and counter-sample material (Al₂O₃, Si₃N₄, ZrO₂, AISI52100 steel) on the coefficient of friction and wear rate of the sintered composites and 316L steel was determined. After the abrasion tests the sample surfaces were examined by scanning electron microscopy. The obtained results show that the tribological properties depend on the test conditions and content of the TiB₂ reinforcing phase.

The paper presents problems that accompany measuring the thermal conductivity of composite insulating materials with a matrix of polymer resins filled with hollow microspheres used in means of short and long-distance transport. To measure the thermal conductivity with measuring apparatuses available on the market, samples with a specific shape, dimensions and accuracy of workmanship are required. During the drying of water-soluble resins, bubbles and surface deformation develop as a result of water evaporation. Machining the samples to obtain flat and parallel surfaces is not recommended due to the possibility of damage to the microspheres. Moreover, pressing the sample plates with a force that exceeds the permissible pressure for the spheres (3÷5 MPa) in order to reduce air-filled gaps, is not recommended due to the possibility of damaging the coating. Inaccuracy in producing the samples significantly affects the accuracy of the thermal conductivity measurement results by direct methods using the heat flow conducted by the test sample.

The article presents an experimental procedure for making a single product - a gear housing, by the hand lay-up technique using a vacuum bag, as part of an adaptation project. The applied technological procedure included using the original element as a model to produce a mold, the production of the mold and the production of two elements from two alternatively reinforced laminates (a chopped-strand mat and a plain-woven fabric), by the hand lay-up method. On the basis of the observations made during the technological procedures and based on evaluation of the manufactured products, it was stated that the hand lay-up lamination technique with additional use of a vacuum bag is a very good and simple method of making single products. The use of vacuum prevents the occurrence of defects typical for classic manual lamination, such as delaminations, closed air bubbles, or (especially) lack of adhesion in low-radius curved areas. It was also found that the original solution consisting in removing the semi-finished product in the form of a part of the hardened stack from the model/form and continuing the lamination of the remaining layers outside the model/form is effective. It has no visible impact on the quality of the product and significantly facilitates demolding. An important issue during the application of vacuum bag assistance is proper selection of the amount of catalyst for the resin. This should be preceded by measuring the room temperature in which the process is carried out and the time of the hand lay-up lamination process - the number of layers should be selected for the predicted resin curing time so that a proper lay-up can be prepared and the vacuum process carried out before the laminate cures. The manufactured elements require slight machining of the technological surplus, which is difficult to avoid when designing a technically simple form for a single or low- series product.

Thermoplastic polyurethane elastomers (TPU), having mechanical properties similar to chemically crosslinked rubbers, can be processed using extrusion or injection molding techniques. Combining extrusion with a foaming process leads to the fabrication of porous lightweight materials with novel properties. These properties can be further modified by applying additives, such as polyhedral oligomeric silsesquioxanes (POSS). POSS are organic-inorganic hybrid nanofillers that could enhance polymer-based composites properties, e.g. mechanical properties or thermal stability. In this work, the foaming extrusion process of TPU, utilizing azodicarboxamide (ADC), sodium bicarbonate (SC) and citric acid monohydrate (CA) as blowing agents (or their mixtures) was described. TPU was modified with two kinds of POSS nanofillers: TMP DiolIsobutyl POSS (TMP POSS) and trans-Cyclohexanediol Isobutyl POSS (TC POSS) to intensify the nucleation of the foaming process and to improve the thermal properties of the TPU matrix. A suitable processing window was determined by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The relations between the type of blowing agent mixture, POSS nanofillers and microstructure/thermal properties of TPU porous composites were evaluated using DSC and scanning electron microscopy (SEM). The blowing agent mixtures, which produce solid residue after decomposition (ADC-CA and CA-SC), influence the nucleation process in the crystalline domains of TPU. The addition of POSS nanofillers strengthens the abovementioned effect and additionally increases the amount of pores in the extrudates, as well as enhances their shape stability.

The work presents preliminary attempts to create a filament for 3D printing (FDM technique) based on a low density polyethylene (LDPE) composite reinforced with shredded windscreen glass. The glass powder was obtained by grinding windscreen glass wastes. PVB (polyvinyl butyral), which is an integral part of safety glass car windscreens, was not removed from the obtained powder. The obtained powder had a range of grain diameters 90÷160 μm. The powder was then mixed mechanically and in an ultrasonic chamber with LDPE granulate. The composites were made by extrusion with one regranulation cycle. The filament for FDM printing was produced by extrusion winding with cooling in open air. A filament with a diameter of 1.45±0.05 mm was obtained. The produced filaments were subjected to a static tension test and SHORE hardness tests. In order to compare the material, the maximum stress recorded at 50% elongation was determined for each tested material. It was observed that along with the increase in the glass content, the strength of the filament decreased slightly. The basic stage in evaluation of the produced materials was to carry out trial prints on an FDM printer. The printing temperature was selected experimentally during a series of trials. The best results were obtained at the print temperature of 250°C and table temperature of 90°C. During printing, an unfavorable effect of filament bending was observed in the printer, below the supplying roller. This effect occurred during printing at a supply speed of more than 1 mm/s. Special additional printing tests with supply rates below 1 mm/s were carried out. This made the printing possible, and it showed the evident superiority of the composites over the neat LDPE. The problem with the stability of filament supply during printing was partially solved by mechanical stiffening of the line between the rollers, using specially printed inserts. The trial prints made from the tested composites occurred to be of better quality than those from the neat LDPE. They show less deformation caused by shrinkage. These effects result from stiffening of the material caused by the addition of hard glass particles. It was found that an addition of a minimum of 30% of the glass particles is required to have a significant effect on the LDPE stiffness.

To perform accurate finite element analysis of composite materials, it is a necessity to enter the correct value of the material properties during model preparation. Since composites consist of at least two components with quite different properties, it is necessary to calculate the resultant properties of the final material. There are a few methods for estimating these parameters. This paper focused on two methods referred to as the Rule of Mixture model, and the Halpin-Tsai model. In the first section, the basic elastic properties of the component materials were cited, then in the next part of paper the elastic properties of the composites were calculated using the aforementioned method. During the calculations both methods were described, along with the range of their application in reality. The parameters were calculated for several composites differing in the percentage of fibers in the composite to present changes in the coefficients on a common graph. All the moduli are collected and presented on graphs. One material was then chosen and used for further analysis. In the next step, finite element analysis (FEA) was performed to estimate the impact of the selected method for determining the material elastic properties on the results of the analysis. FEA analysis was performed using ANSYS Workbench 19.1 ACP Pre/Post software, which allows users to manually enter the properties of the studied materials. The sample was modelled as a laminate, consisting of layers – laminas arranged angularly in relation to each other, which are arranged symmetrically with respect to the median plane of the sample. Two analyses were carried out and then the differences in the final results of the strain values were presented in table form, which indicate the percentage differences between them. This allows one to specify which model of estimating the elastic properties is more precise in the studied case and when it is worth using a more precise method of estimating these values.

The paper presents an attempt to estimate the difference in the intensity of the curing process of a polyester resin: without any filler and filled with fragmented glass fabric. Curing of the resin samples was carried out at room temperature. The temperature-time course of the process and gel time were recorded for each sample. On the basis of the obtained results and the conducted observations, it was found that filling the resin with fragmented glass fabric caused a decrease in the peak temperature of the curing process and increased the time of reaching this temperature. These effects were found to intensify with an increase in filler weight (inhibitory effect of the filler). A slightly longer gelation time was also found for the filled resin in comparison to the unfilled one. The observed effects indicate an increase in the thermal insulation of the curing mass along with an increase in filler content. They also indicate that the presence of fibers leads to stabilization (improvement of repeatability) of the resin curing process. The work is a continuation of earlier work aimed at experimental evaluation of the behavior of curing resins, which in turn will help to systematize the practical knowledge in this field. Thus, it finally meets the expectations of users and processors of curable resins.

The aim of this work is to examine the effect of the layer configuration (lay-up) of carbon 3k/IMP503Z40 epoxy composite elements on the specific energy absorption (SEA) effect in the process of progressive crushing of composite tubes. Composite tubes made of Impregnatex Compositi prepreg with a dry areal weight of 160 g/m² plain weave and unidirectional prepreg (UD) 200 g/m² on an epoxy matrix were tested. The resin content in both prepregs was 47%. Using these two materials, tubes with different ratios of axial and hoop fibers, in two sizes with an inner diameter of 42 and 20 mm while maintaining a constant ratio of wall thickness to a diameter of 0.05 were made. The samples were unilaterally chamfered at the angle of 70°. Then, tests of progressive crushing of the samples under dynamic conditions by means of a drop tower and an additional initiator were performed. A new factor was introduced to describe the mass fraction of the axial fibers. SEA was calculated, which indicated that the higher the share of axial fibers, the greater the SEA for both types of samples and it was indicated that there may be a scale effect.

The self-heating effect occurring during the fatigue loading of polymeric composite structures subjected to cyclic loading or vibration is a result of energy dissipation appearing due to the viscoelastic properties of the matrix of such composites. The occurrence of the self-heating effect during the operation of structural elements is very dangerous, since the increasing selfheating temperature intensifies the initiation and propagation of fatigue damage, and may significantly shorten the residual life of such elements. Following this, it is necessary to control this process. The theoretical models developed to date may be inaccurate in predicting the residual life of a structure subjected to fatigue with the appearance of self-heating, especially after the initiation of structural damage. Therefore, the authors proposed the empirical model based on estimating the parameters from the self-heating temperature profiles with statistical analysis of these parameters, which allows one to determine the estimators and predict the residual life of composite structures working in such conditions in more accurate way.

The paper presents an experimental and numerical study investigating the load carrying capacity of thin-walled composite structures with an omega-shaped cross-section subjected to axial compression. The tested profile was made of carbon-epoxy laminate with symmetrical arrangement of the layers [0/90/0/90]s. The experimental tests were performed on a universal testing machine - Zwick Z100, under full load conditions until total failure of the structure. The post-critical equilibrium paths of the construction were determined, defining the relationship between compressive load and deflection and enabling the FE models to be validated. Based on the obtained post-critical equilibrium paths, the critical load of the construction was determined using well-known approximation methods. Simultaneously, numerical analysis was carried out by the finite element method using Abaqus® software. The critical state was determined via linear eigenvalue analysis, and the critical load and corresponding first buckling mode were estimated. The next stage of numerical analysis involved solving the nonlinear stability problem of the structure with initialized geometric imperfection reflecting the first buckling mode of the composite material. The geometrically non-linear problem was solved by the Newton-Raphson method. The load capacity of the composite profile in the post-buckling state was determined by the progressive failure criterion which estimates damage initiation in the composite material using the Hashin criterion. Progressive failure analysis is described with the energy criterion describing the stiffness degradation of finite elements. The obtained numerical simulation results showed very high correspondence with the presented experimental results conducted on real structures, which confirms the precise preparation of the developed numerical models of the composite structures.

The subject of the experiment and numerical research is a simply-supported thin-walled box beam with a span of 2.00 m, created by gluing two composite GFRP shells. The beam was subjected to a three-point bending test controlled by displacement in the range from 0 to 300 mm. An experimental bending test, numerical modelling and simulations of this test as well as validation of the modelling and simulation were carried out. In comparison with the authors’ previous publication, adjustments and enhancements include: correction of the GFRP material constants and friction coefficients; testing the key numerical parameters of the geometrically and physically non-linear task, i.e. an iteration step in the implicit algorithm, a convergence tolerance coefficient, FE mesh density; testing the use of the Glue contact option in the MSC.Marc FE code for modelling adhesive joints; quasi-optimization of the ply sequence with the maximum load bearing capacity as the objective function. The parameters and options of numerical modelling and simulation of glued composite shells in the MSC.Marc system were determined, useful for detailed design calculations of composite FRP structures.

The development of a sintered copper matrix composite with a small addition of carbon nanotubes (CNTs), which improves its mechanical strength without a decrease in electrical conductivity is of practical importance. Therefore, in the present paper the parameters of ball milling of a Cu+CNT powder mixture were optimized in order to obtain the highest refinement of particles of such a composite material. Investigations carried out with the help of scanning electron microscopy and sieve analysis revealed that the average particle size of the powder decreases with an increase in the volume content of the carbon nanotubes. The presence of carbon material should limit grain growth during the hot pressing of composite material, allowing much smaller grain sizes and accompanying high hardness to be obtained of the resulting compacts, as compared with similarly processed copper powder.

At present due to the emergence of new methods of synthesising starting powders and their consolidation, Al₂O₃ based high-strength ceramic materials toughened by ZrO₂ (ZTA) are widely used as structural materials for various purposes. It is known that the material properties depend on the properties of the starting powders. Combined methods of powder preparation essentially extend the possibility to vary the powder properties. The purpose of this work is to produce a finegrained powder of the composition (mol%) 58.5 α-Al₂O₃ - 41.5 ZrO₂ (Y₂O₃, CeO₂) by a combined method (hydro-thermal synthesis in an alkaline medium/mechanical mixing). The resultant fine-grained powder was heat-treated at 400, 550, 700, 850, 1000, 1150, 1300, and 1450°C with holding for 2 hours at each temperature. The properties of the synthesized powders were characterized by differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and specific surface measurements (BET). The microstructural and phase analyses were conducted by petrographic study. The powder morphology varies continuously topologically. The agglomerates after mechanical mixing had an irregular shape up to 1450°C. A tetragonal solid solution based on ZrO₂ (T - ZrO₂) and α-Al₂O₃ was identified in the powder after mechanical mixing. T-ZrO₂, as well as a monoclinic solid solution based on ZrO₂ (M-ZrO₂) and α-Al₂O₃ were identified after heating at 1450°C. The research results will be used for the microstructural design of ZTA composites.

A method was developed to manufacture Ti₃SiC₂ MAX phase preforms characterized by open porosity. Samples compacted from elemental powders of Ti, SiC and C with the molar ratio of 3:1.2:1 were heated and synthesized in a microwave field under atmospheric pressure. As this particular composition of elements exhibits rather low reactivity, it was necessary to apply the “coupled” mode of the SHS method. The initiated synthesis first proceeded with the formation of Si-Ti intermetallic and TiC precipitates, whose highly exothermic reactions resulted in a significant increase in temperature to ca. 1800°C. Next, these phases were almost completely transformed into a plate-like Ti₃SiC₂ MAX phase forming the porous structure of the samples. Although the majority of the synthesized material consisted of Ti₃SiC₂, some inclusions such as TiSi₂, TiC and SiC were also found and identified in the material by the means of scanning electron microscopy and XRD analysis. The manufactured preforms can be used for components working in extreme conditions (heat exchangers, catalyst substrates, filters) or as a reinforcement for composite materials.

The presented work is a continuation of tribological research on alumina/graphene composites. In our previous publication the results of wear tests on the above mentioned composite at room temperature, but also at temperatures of 150, 300 and 500°C were presented. The studies showed that this composite is promising in relation to pure alumina at ambient temperature and 150°C. In order to determine more precisely the temperatures at which the tested material can work, abrasion tests were carried out at two additional temperatures, 80 and 200°C, and the results are presented in the following paper. Noticeable plastic deformation and wear greater than at room temperature was detected already at 80°C but it was still significantly lower than at 150°C when the composite wore significantly less than pure alumina. The test carried out in 200°C gave results similar to those for 300°C, which indicates significant degradation of the material at this temperature.

The aim of the conducted research was to determine the effect of filler in the form of microspheres from fly ash being a product of bituminous coal combustion on the functional properties of polyethylene. Comparative analysis of unfilled polyethylene and polyethylene with additions of 5, 10 and 15% (wt.) fly ash from bituminous coal was carried out. Tests of the mechanical properties were performed: tensile strength, hardness determined by the Shore method and the ball indentation method. Color and gloss analysis was also performed. On the basis of the conducted tests, it was found that the modification of polyethylene with fly ash from coal combustion has a significant impact on the functional properties of the tested materials. The molded parts from unfilled polyethylene exhibited the lowest value of hardness, while the largest value of hardness was obtained by parts made of polyethylene with 15 wt.% filler content. The content of fly ash from bituminous coal combustion also affects the tensile strength and elongation of the tested materials. As the filler increases, its tensile strength decreases. As a result of the addition of the filler, changes in the coordinates describing the color, as well as a reduction in the brightness value and a reduction in the gloss degree for the angles of incidence of 60° and 20° were noted. The presented research results indicate that producing polyethylene composites with the addition of microspheres from fly ash originating from bituminous coal combustion gives the possibility to obtain composites with significantly better mechanical properties as compared to unfilled polyethylene. The use of fly ash from the combustion of bituminous coal as a filler results in obtaining an inexpensive filler compared to fillers used in industry today. At the same time, it contributes to reducing the amount of waste generated from the combustion of bituminous coal. The test results give the possibility to use the composites produced in various industries as a raw material for the production of various engineering elements.

In the article, a new composite was studied as a potential biomaterial. The effects of the interaction of distilled water with the polished surface of an AZ31 magnesium matrix composite reinforced with open-celled glassy carbon foam fabricated by the pressure infiltration method were investigated. The experiment was conducted in the time range of 1 minute - 4 hours and the microstructure was examined by scanning electron microscopy. In the initial unetched material, at the glassy carbonmetal interface, a zone of needle-like phases was detected. After a 1÷10 minute interaction with the water, disintegration of that zone was revealed and that type of material degradation proceeded deeper into the composite as the time increased. Another type of corrosion was observed in microareas of the magnesium alloy matrix, but only after approx. 1 hour when corrosion pits were recorded. The results of X-ray mapping showed an increase in the oxygen concentration in both types of corrosion products, but the reason for the corrosion in the region between the carbon foam and the AZ31 matrix is degradation of the hydrophilic aluminium based carbide phases, while in the composite matrix, typical electrochemical corrosion of magnesium occurred.

The paper presents a description of preliminary trials of covering glass-ceramic fibers with polymer resins intended for new fiber optics claddings. It occurred to be impossible to obtain a polymer film on the fibers without the effect of forming droplets using an epoxy resin with a relatively low viscosity (0.58 Pa•s). Reducing the thickness of the applied film by immersing the initially covered fiber ina solvent allowed the authors to obtain a uniform thin coat of 0.25 μm, which is too small for the practical application. Applying a gel-coat (high viscosity) as a covering liquid allowed a high thickness coating to be obtained. However, the thickness was very inhomogeneous - it varied from 2 to 30 μm. The most promising coating was gained with an acetone-based dispersion of ceramic powders with a viscosity of 0.8 Pa•s. It allowed the authors to obtain a coating thick enough to be technically applicable (> 10 mm), without the presence of droplets. This is an important guideline for further work on obtaining claddings for new optical fibers. The obtained results show the importance of viscosity and internal cohesion of the applied liquid for the effectiveness of its application to a solid base. Modifying the viscosity of liquids can in many cases be a technically simpler solution than improving wettability between the liquid and the given base.

The paper presents a method to determine the thermal conductivity of composite insulating materials containing ceramic microspheres, in which there is a vacuum. The matrix of the tested composite is acrylic resin, and the strengthening phase is ceramic microspheres. Preparing of samples from such material for testing in a plate apparatus is difficult due to damage to the spheres during processing and the formation of air gaps between the plates. The described method uses the amount of electricity consumed by the water heaters to maintain the set temperature. The essence of this method is to compare the energy consumption of the tank coated with the tested composite material with that by an identical tank coated with an reference insulation with a known thermal conductivity (PUR). A necessary condition is a similar drop in temperature on the test and reference insulations.

The development of a new deposition method allowing to obtain thick composite coatings is of both scientifically and practical importance. The one presented in this paper is based on a negative side effect taking place during the mechanical synthesis of alloys, i.e. sticking of milled material to the surfaces of both the vial and balls. The experiment covered the comilling of NiAl (~45 μm) with 15 wt.% CrB₂ (~40 μm) powders together with nickel platelets used as the substrates and steel balls. The above processing performed at 200 rpm resulted in a steady increase in the thickness of the rubbed-in buildup on the platelet surfaces allowing coatings of 4, 11, 22 and 33 μm to be produced after 4, 8, 16 and 32 hours. The OM, XRD and TEM investigations showed that such coatings are characterized by a gradient microstructure with heavily dislocated but coarser grains near the substrate and a more porous inner part formed with rounded well fused agglomerates of greatly refined crystallites. The CrB₂ were only slightly larger than the NiAl ones and were distributed quite uniformly. Most of the coating was found well fused with the substrate, but occasional voids and porosity at the substrate/coating interface were also noted. It is worth noting that applying the proposed method allowed the authors to produce a thick, gradient and mostly nano-crystalline NiAl and CrB₂ composite coating.

The paper compares the influence of the type and number of composite reinforcement layers on the impact resistance, as well as the effect of the matrix type. Carbon, aramid and carbon-aramid fabrics were tested, and block copolymer styrene-butadiene-styrene and epoxy resin were also tested. In addition to impact tests, investigations were also carried out on the adhesion of the coatings, without reinforcement and with one layer of fabric, to the steel substrate. The highest values of pulloff strength were obtained for the coatings based on the SBS copolymer reinforced with fabrics. In the case of the coatings reinforced with aramid and aramid-carbon fabric, both adhesive and cohesive damage occurred during the pull-off test.

Alumina materials are of great interest due to their high wear resistance, resistance to corrosion, high strength and low friction. However, studies show that a graphene addition can significantly reduce wear and friction. Even a small addition of platelets results in noticeable changes in the material properties. The presented work describes the results of the ball-on-disc test conducted on two friction pairs: alumina-alumina and alumina/graphene composite - alumina. The tests were conducted at four temperatures: 20, 150, 300 and 500°C in air. Surface profile geometry measurements after the test were used to determine the wear rate. Observation of the surface microstructure after friction was carried out using a scanning electron microscope. The tests showed improvement in the wear resistance and a decrease in the friction coefficient of the composite tested at room temperature compared to pure alumina, while the use of elevated temperatures adversely affected the composite.

The application of silica-based fillers for polymers and nanocomposites is a subject of extensive research, mostly due to the demand for new materials of improved physicochemical, mechanical or thermal properties. In this paper we present a new, one-pot sol-gel (OPSG) method to synthesize fillers for polyolefins. The developed method assumes direct synthesis of the filler together with its modification upon the addition of organofunctional silane. It allows fillers with controlled porosity and hydrophobic properties to be obtained, which undergo better dispersion in a polymer matrix. The characteristics of the obtained composites were defined by thermal analysis, as well as tensile and impact tests. The contact angle was measured by the sessile drop technique to determine the hydrophobic-hydrophilic properties of the fillers. Morphological analyses were performed using SEM, surface area and pore volume measurements. The one-pot method is a preferred alternative to the multi-step synthesis methods for synthetic fillers.

The work explored the possibility of producing Al₂O₃-Ni gradient composites using non-absorbent molds in a high-speed centrifuge. As a result of the centrifugal force, the mass was compacted and the solvent was separated from the solid part. The influence of rotational speed and the change in the solid phase content in the slurry on the obtained microstructure of the composites was investigated. The produced composites were characterized on the basis of macroscopic observations of the obtained samples immediately after the casting process (green body) and after the sintering process. To determine the gradient of the metallic phase, the observations were made on cross sections of the samples. Densification of the sinters was determined by the Archimedes method. The obtained results showed that using an appropriate correlation of technological parameters, i.e. rotational speed and solid phase content in the slurry, enables the fabrication of Al₂O₃-Ni composites with a microstructure gradient by the centrifugal casting method using non-absorbent forms. It was found that with an increase in the solid phase content in the mass, a clear boundary is formed which separates the area containing only ceramic (Al₂O₃) and metallic (Ni) particles.

The study presents research on the influence of the size of solid lubricant inclusions-graphite on the properties of pressureless sintered SiC-graphite composites. The purpose of these composites is to achieve a self-lubricating effect between the working elements of a friction seal. For this purpose, studies were carried out, on the basis of which the composite with the inclusion size that provides the optimal mechanical andtribological properties was selected. The apparent density, hardness, bending strength, abrasive wear resistance, friction coefficient and linear wear in contact of the same kind of material pairs were determined. Mechanical and tribological tests were correlated with qualitative and quantitative microstructure analyses, on the basis of which it was found that SiC-graphite composites with inclusions not larger than 0.056 mm meet the requirements for the materials used to produce self-lubricanting elements of face seals. It was then observed that small inclusions of graphite are more uniformly distributed in the SiC matrix.

This work describes polyester matrix composite materials with diversified reinforcement materials, namely glass, carbon, and a natural material (jute). These reinforcement fibres were utilised in the form of fabrics with a canvas-like weave and basis weight ranging from 300÷400 g/m². The mass fraction was uniform in each of the materials that were produced, namely 40% of the baseline in comparison to the materials that were subjected to testing. The composites were produced by the vacuum pressure infiltration method, RTM (resin transfer moulding), thereby creating laminates. To assess the mechanical properties of the composites, static tensile strength tests were carried out according to PN-EN ISO 527-1:2016; the bending strength was determined according to PN-EN ISO 178:2011, and the impact strength was tested by the Charpy method according to PN-EN ISO 179-1:2010. The density of these composites was determined by the hydrostatic method according to standard PN-EN ISO 1183-1:2013-06.

Composites produced in nature, such as mollusc shells, are renowned for their unique structures and exceptional properties. The crystallographic characterization of different shells as well as their physical and chemical properties have always attracted the interest of researchers. Much information is available at present, however, most of it concerns sea molluscs. We focused on the microstructures and chemical composition of the shell of land snails of the Cepaea genus. New aspects of the microstructure of shells have been shown through the use of a scanning electron microscope (SEM) equipped with an EDS X-ray detector, and X-ray diffractometry (XRD). The study shows that all the tested snail shells are characterized by a typical crossed-lamellar structure and are built of aragonite. Small differences in the chemical composition of the shells as well as differences in the size of the crystallites and different proportions of the amorphous phase were also noticed.

The aim of this paper is to present synthesis and characterization routes of hybrid polyurethane viscoelastic foams reinforced by - inorganic nanoaddities. Recently, much attention has been given to polymer nanocomposites made with POSS (Polyhedral Oligomeric Silsesquioxanes) - a family of siloxane material consisting of inorganic silicon-oxygen core and organic functional groups. Functionalization of POSS enables formation of chemical linkages with polymer matrix and increases compatibility between the organic and inorganic components. Our research focused on the modification of polyurethane materials by functionalized POSS. Octa(3-hydroxy-3-methylbutyldimethylsiloxy) POSS containing eight hydroxyl groups and 1,2- propanediolisobutyl POSS with 2 hydroxyl groups were chosen as additional co-reagents which were mixed by ultrasound homogenizer in polyol phase. POSS was added in amounts 5, 10 and 15% by weight of polyol, and reacted with diisocyanate (TDI) to obtain PU/POSS composite. The effects of incorporation of POSS on the mechanical properties of PU-based hybrid composites were presented. Moreover, the morphology of PU/POSS hybrids was investigated by means of wide-angle X ray diffraction (WAXD) and scanning electron microscopy (SEM) techniques.

The article describes the course and results of research on a composite laminate. Specimens were made from glassreinforced epoxy resin using the hand lamination technique with the fibres arranged unidirectionally along the specimen. The dimensions were selected on the basis of DIN EN ISO 14125. Strain gauges were placed on the surface of every specimen, then testing was conducted - three point bending. The specimen was placed so that the strain gauge was at the stretched side during bending in order to measure the strain. The stress was also calculated analytically, based on the process parameters. As a result, the theoretical stresses were compared with the experimental ones.

The study describes the results of tensile strength tests of hybrid laminates composed of thin titanium layers and glass and carbon fibre reinforced polymer layers. The tests were conducted at −120, RT (23°C) and 85°C. The tests allowed the basic mechanical properties to be determined, including: tensile strength, Young's modulus and strain at failure. The tests proved that as the temperature decreases, the strength of titanium/glass fibre reinforced polymers increases by 21 to 26% depending on the configuration, while the strength of titanium/carbon fibre reinforced polymers decreases by 6 to 8%. The Young's modulus values for all the tested systems increase by 3 to 7% as the temperature drops. A different tendency was observed regarding the strain at failure which decreases by 1 to 11% as the temperature drops. The tensile strength test results for the increased temperature (85°C) differ only slightly from those obtained at room temperature. The macroscopic analysis of the failed specimens revealed the existence of characteristic, prevailing forms of failure, namely breaking fibres, matrix cracking, including delamination and permanent deformation of the titanium layers.

The paper presents the preliminary results of studies on obtaining copper-based composite materials strengthened with silicon carbides. Electrolytically obtained copper powders were used as the matrix. The sinters were characterized by different SiC contents (0, 5, 10, 15 wt.%). The materials were consolidated by one-sided pressing followed by sintering (T = 800°C, t = 1 h). One-sided pressing was carried out at the pre-set pressing pressure of 60 kN and at the rate of 200 N/s. The research was performed on powders, mouldings and sinters. Investigations of the composites comprised: microscopic examinations (SEM), chemical composition analysis (SEM), XRD measurements, the density of the composites was determined, and a quantitative evaluation of the porosity of the composites was carried out.

The paper discusses and attempts to analyze the impact of the method of forming fibrous composite materials on the quality of the laminates. The model assumes that the composite consists of components having individual physico-mechanical properties with a symmetrical structure [0/90/0/90]s. This article uses experimental data of a contact-formed composite (Composite I) and a vacuum bag composite (Composite II) with a polyester matrix (Firestop 8175-w-1) reinforced with E glass matte fabric. Before the samples were cut, the parameters and technological criteria of the formed composite were determined such as the amount of resin and soaking time of the composite reinforcement with the polymer resin. The influence of matrix plastification and a more packed structure in the produced composites on the scale effect (for samples with larger and smaller measuring bases), the dispersion and mean value of strength from the time of aging were determined.

Fireproof textiles must exhibit high heat resistance. Many methods to improve this property are known. They can be achieved, for example, using special chemical additives during fiber production. In the paper the use of a nanocomposite layer is proposed. NATAN and PROTON fireproof textiles were coated with a TiSi(N) nanocomposite layer using magnetron sputtering technology. Three layer thicknesses of 200, 300 and 400 nm were applied. The thermal barrier effect for heating up to 100 and 330°C was studied on specially designed testing equipment. The influence of the layer thickness on the textile heat resistance was visible at 100°C. For the thickest layer a worse effect was observed, which could be caused by the thermal conductivity of the composite layer. However, the proposed layer raised the heat resistance of the textiles.

In the present paper, a new approximate analytical formula for the effective conductivity of 2D dilute composites with poorly conducting circular inclusions and cracks on the interface between the inclusions and the matrix is established. This formula is proved by Maxwell's approach and Keller's identity using advanced complex analysis. The obtained formula is used to determine the effective thermal conductivity of a composite material being an aluminum matrix based on Al-Mg-Si alloy reinforced with Al₂O₃ particles with the average size of about 25 microns and a volume fracture of 20%. The computer simulations results are presented in tables and illustrated by figures. It follows from the derived formulas that cracks reduce the effective heat conductivity about 9% with respect to the material without cracks.

The preparation of powder agglomerates used in the plasma spray deposition processes, and especially their homogeneity, turned out to be highly important at the moment when the phase ratio in the composite coatings began to differ from that in the starting materials. The present experiment was aimed at comparing the microstructure and phase composition of hot pressed or sintered NiAl and CrB₂ powders. The use of SEM and XRD methods showed that only sintering leads to a reaction of the chromium diboride with the intermetallic matrix. As a result of this process, Ni_0.5Cr_1.5B₃ phase precipitates on the CrB₂ particles. Consequently, the agglomerates formed after crushing the compacts obtained by sintering are much more homogeneous than those formed by hot pressing.

The article presents the fundamentals of the manufacturing, structure and selected properties of composite coatings (RGC) developed at the Silesian University of Technology designed for the aviation industry. The tribological properties of the developed coatings were compared with the properties of coatings used to date (TLML). The primary purpose of the coatings developed by the authors is to extend the time of correct operation of selected contacts of aircraft piston engines after the loss of lubrication due to a failure during flight. This time is necessary to fly to a safe landing place. Ensuring correct operation of the contact, i.e. maintaining the coefficient of friction at a level to prevent seizing, is possible due to a coating of a composite layer containing solid lubricants on the sliding surfaces. In the RGC coating, it is a glassy carbon and in the TLML coating it is molybdenum disulphide. During sliding with an insufficient amount of oil, more intensive wear of the coating takes place. Since the lubrication does not work, wear products are removed from the friction zone much more slowly. A mixture is formed from the wear products of the solid lubricant and oil residues, which is deposited on the cooperating surfaces, reducing friction. Even after the coating was worn off, the coefficient of friction in the conducted tests did not exceed 0.04. The developed coating can work at 120°C, with pressure p = 0.4÷2.0 MPa and at sliding velocity v = 0.55 m/s up to 30 minutes without being completely worn out. The TLML coating after about 24 minutes was worn out.

In this work results of the preparation of bentonite/nAg nanocomposites were presented. In the first stage, the bentonite sorption properties were determined, including the equilibrium and kinetics parameters of the sorption process of silver ions on the bentonite. The study analyzed the filler sorption properties for different concentrations of silver ions in solution. The equilibrium sorption data were analyzed using Freundlich, Langmuir and Temkin equations. It was found that the best fit is given by the Freundlich equation. Analysis of the kinetics of the sorption process showed that the pseudo-second-order equation was characterized by the best fit for the experimental data, suggesting the chemical character of the adsorption process. In order to obtain a nanocomposite, silver ions contained in the composite were subjected to a reduction process using tannic acid with stabilizing and reducing properties. The obtained bentonite/nAg nanocomposites contained silver nanoparticles in the range of 162÷266 mg/g. The structures of the nanomaterials were studied by XRD and SEM methods.

The article presents the issues of recycling materials made of plastics and composite materials based on a plastic product. The way of preparing samples made of polyester resin being the matrix with cotton, jute and glass fibre reinforcement was described. Moreover, the results of combustibility property tests of the prepared composite materials were shown. The studies were carried out according to the UL 94 standard, used by American Underwriters Laboratories. The results of the tests were presented in the form of final conclusions.

The self-heating effect occurring during the cyclic loading of materials that exhibit thermoviscoelastic properties, depending on the loading conditions, may develop according to two possible scenarios: stationary and non-stationary. Since stationary self-heating has not been not previously studied in terms of the criticality of the self-heating effect, it is essential to perform such a study to better understand the degradation processes in this scenario and to confront the results with the criticality of non-stationary self-heating. In the present study, the experimental results on fatigue testing following the stationary self-heating scenario are presented and discussed. In order to characterize the degradation process, both self-heating temperature distributions and their evolution as well as acoustic emission measured at various self-heating temperature ranges were analyzed. The obtained results allow the influence of the self-heating effect on the residual life of composite structures under the stationary self-heating scenario to be estimated.

In this work the microcrystalline cellulose (MCC) filler was chemically modified by esterification with succinic anhydride (SA) in order to improve the compatibility of MCC with the hydrophobic polymer matrix. The effect of the microwave irradiation and conventional heating on the chemical structure, particle morphology and thermal stability of the cellulosic filler was evaluated by FTIR/ATR, TGA and light microscopy. The extent of surface modification of microcrystalline cellulose gradually increased with an increasing reaction time up to 90 min, and the effect was significantly pronounced under microwave irradiation as compared to conventional heating. A decreasing decomposition temperature was observed for the samples modified with SA as compared to the reference sample as a result of introducing functional side groups into the cellulose backbone and developing the surface of the MCC powder. A decrease in MCC particle sizes was observed as a result of chemical modification, especially under microwave irradiation, indicating partial hydrolysis of the amorphous regions of cellulose in an acidic environment. Smaller particles can be more equally dispersed in a polymer matrix. Applying microwave irradiation enhanced the efficiency of surface modification and produced MCC with a wider range of surface properties. Microcrystalline cellulose with adjusted surface properties can be applied as a reinforcing filler for fully biodegradable ‘green’ composites.

A method was developed for manufacturing Al-Si alloy matrix composites reinforced with MAX phases by squeeze casting pressure infiltration of porous preforms. MAX phases in the Ti-Al-C system were synthesized using self-propagating hightemperature synthesis (SHS) in the microwave assisted mode in order to obtain spatial structures with open porosity consisting of a mixture of Ti₂AlC and Ti₂AlC i Ti₃AlC₂. The manufactured composite together with a reference sample of sole matrix material were subjected to the testing of thermal properties such as: thermal conductivity, thermal diffusivity and thermal expansion in the temperature range of 50÷500°C, which corresponds to the expected working temperatures of the material. The specific heat and mass change during heating were also established by means of thermogravimetric analysis. The obtained thermal conductivity coefficients for the Al-Si+Ti-Al-C composite were higher than for the sole MAX phases and equalled 27÷29 W/m•K. The thermal expansion values for the composite material were reduced two-fold in comparison with the matrix.

The work develops the original methodology of design calculations for GFRP composite box footbridges. This methodology was applied to the original structural solution of a composite pedestrian-and-cyclist bridge with a 12.00 m span length and a 2.50 m platform width. The footbridge structure includes a number of original solutions regarding the superstructure, crosssection, bearings, reinforcement of support zones, transverse braces, balustrades, and railing post-platform connections. The design criteria for a GFRP composite footbridge were formulated based on the latest national standards for the design of footbridges made of conventional materials (steel, concrete) and the standard for the design of GFRP laminate tanks. The ultimate criterion for the composite superstructure was formulated using the Hashin-Fabric failure criterion and a global map of the effort index. Moreover, the serviceability criterion for the vertical deflections of the superstructure, pedestrian comfort criterion and global buckling criterion were developed. The advanced numerical modelling and simulations of the footbridge were carried out using MSC.Marc FE code. The modelling and simulation methodology, as well as the results of identification and validation tests published in the previous works by the authors were used. The results of simulation of the ultimate, serviceability and buckling limit states, corresponding to the adopted ply sequences of the laminates in the individual GFRP shells, are presented. Due to the fulfilment of all the criteria with significant margins, further numerical analyses of a footbridge with fewer laminations and design according to the Eurocodes are purposeful.

The paper presents the process of producing composite material by the vacuum bag method and its numerical analysis. The composite is made of three layers of two-directional combimat with a [0.90] orientation. Then it is cut at angles and subjected to a tensile test in the Laboratory of Composite Materials, Kielce University of Technology. The data obtained from the tensile test were used to construct three tubular elements that were designed in the ABAQUS program using the finite element method. The tube was treated as a thin-walled shell component, at both ends infinitely rigid rod-shaped Rigid links are formed, at the center of their intersection the point of attachment is generated. On both sides of the rigid restraint, the element is subjected to a uniform internal pressure of a 10 MPa amplitude, which would be very difficult to obtain under laboratory conditions. The conducted experiment gives very precise information about the stresses created in the composite and the behavior of both the fibers and the matrix at different layup angles.

The paper presents the results of friction and abrasive wear measurements of composites in the α-alumina/tetragonal zirconia system. Two types of materials with mutually interpenetrating phases in a continuous manner were investigated. Pure alumina and zirconia samples were used as the reference materials. Ball-on-disc tests were conducted at 20 and 500°C. An alumina ball was applied as the counterpart. The tests showed that the composites have a significantly reduced wear rate and friction coefficient when compared to monophasic materials. Improvement of the properties was noticeable especially at the elevated temperature.

The aim of this work was to fabricate Al₂O₃-ZrO₂-Ti composites by slip casting and to analyse the influence of a pure titanium addition on the microstructure and density of the composites. For this purpose, two groups of samples were prepared by slip casting, with and without titanium. Experiments were performed using the samples: Al₂O₃ + 10 vol.% ZrO₂ and Al₂O₃ + 10 vol.% ZrO₂ + 10 vol.% Ti. The composites were characterized by XRD and SEM. Moreover, the density was measured using the Archimedes method. The hardness was measured as well. The obtained composites had a homogeneous microstructure and high relative density. It was found that a phase transformation in ZrO₂ occurred. The titanium content as a ductile phase can slightly reduce the Vickers hardness of the composites.

The predictions of major effective medium models and 2-dimensional numerical models implemented in Ansys Fluent were tested against the results of experimental measurements of macroscopic thermal conductivity for a polymer filled with aluminum powder. The examined composite may be regarded as a representative of materials used for heat management purposes, for example for the manufacture of electronic device housings. The study demonstrates the effect of particle shape and imperfect filler-matrix interface on the theoretical value of thermal conductivity of the considered material. It also creates the opportunity to discuss the versatility and accuracy of various methods devised to predict the effective thermal conductivity of heterogeneous materials. It was found that the effective medium approximation proposed by Duan et al., which considers the effect of the particle aspect ratio, outrivaled other predictive schemes in accuracy and cost-effectiveness. Effective medium approximations that assume spherically-shaped reinforcement as well as finite volume models implemented in Ansys Fluent, greatly underestimated the parameter in question.

Verification of the correct modeling of the flat state (on the example of a sample) was carried out using ABAQUS finite element analysis, by entering in the program, the mean values of samples cut at different angles to the reinforcement (mato E-glass fabric). Then, from the same material a tubular element subjected to special loads, made possible thanks to a rigid element (in the form of rods) so-called Rigid Links, was modeled.

This paper presents the study of the detection of "artificial" defects by nonlinear techniques based on the cutting forces recorded during milling process of composite material. The "artificial" defects are intentionally drilled holes of different diameters made in carbon fiber reinforced plastics. The cutting force was analyzed by recurrence plots and recurrence quantifications analysis. The main purpose of this work is to determine the size of an artificial defect that is possible to detect as well as select the recurrence quantifications for damage detection.

This article discusses a new model of the centrifugal casting process which uses the full Eulerian approach to modelling composite suspension dynamics. The proposed model, in contrast to models based on the Lagrangian approach, allows one to consider such important phenomena as the presence of maximum packing of reinforcing particles, or the change in viscosity suspension caused by changes in the reinforcement volume fraction. These phenomena are essential for the final result of the composite casting process. The paper presents the results of numerical experiments using the developed model. Simulation of the casting process of the AlSi7MgSr (AK7) aluminium alloy with silicon carbide and graphite was performed. The results showed that the developed model of the centrifugal casting process enables one to recognize the phenomena that are impossible to capture by measurement techniques available today.

Smart self-healing epoxides have attracted immense interest in the industry due to their capability to prevent crack propagation and increase material service life. Self-healing can be achieved via a number of approaches, where microcapsule-based systems are deemed to be the closest to market implementation. The work presented here demonstrates the effect of polymeric microcapsules made of poly(urea-formaldehyde) on the Charpy impact resistance of a standard epoxy matrix. Poly(urea-formaldehyde) microcapsules containing epoxy resin (EPIDIAN 52) and organic solvent (Ethyl phenylacetate) were prepared using in-situ polymerisation in an oil-in-water emulsion as described in the literature. The Charpy impact tests were performed on specimens made of neat epoxy resin (EPIDIAN 52) - amine hardener (Z1) as well as for the epoxy filled with microcapsules with 1, 2.5, 5, 10 and 25 wt.%. The test results have shown that the presence of brittle and spherical additives has a detrimental effect on the mechanical properties of the polymer, resulting in a maximum 80% reduction in impact strength for the samples with the highest content of microcapsules. In addition, the fracture surfaces of the impacted specimens were investigated using a Scanning Electron Microscope (SEM). Significant differences were observed between the reference samples and those containing microcapsules, particularly when the microcapsule weight fraction is high.

Inadequate adhesive strength of the reinforcing fibers to the matrix in composite materials causes their delamination, which reduces the bearing capacity and durability of the defected product, and in the case of pressure vessels or pipelines, may cause their depressurization. One of possible methods to improve the adhesive strength is to coat the reinforcing fibers by the sol-gel method with organosilica coatings. Silane coatings serve two purposes: 1) the film binds chemically to the surface of the glass fiber, 2) wetting is improved by an increased chemical affinity of the resin to the fiber. Carbon and aramid fibers are usually not coated in this manner, resulting in inferior adhesive properties. In this study, organosilica materials were obtained by the sol-gel method using various silica precursors: methyltrimethoxysilane (MtMOS), ethyltriethoxysilane (EtEOS) and tetramethoxysilane (TMOS). The materials were deposited on glass fiber and hybrid carbon/aramid fiber textiles, resulting in a change in the surface properties. The chemical structures were characterized by Raman spectroscopy, indicating the presence of groups characteristic for silica, as well as the presence of functional organic groups connected by silicon-carbon bonds. The surfaces of the coated fibers were observed by scanning electron microscopy (SEM), indicating undesirable fiber bonding by the coatings obtained using the MtMOS and TMOS precursors, while no such bonding was observed for the coating obtained using the EtEOS precursor. The wettability of the glass fibers by epoxy resin was measured using the electro-optical method, revealing that the coatings made of the MtMOS and TMOS mixture improved the wettability of the fibers with epoxy resin, facilitating adhesion.

The paper presents the results of studies on the degree of wear of commercial dental burs with a diamond coat of the same diamond grain size. The assessment comprised burs designed for palatal development and also burs intended to prepare tooth tissues by grinding. Observations of worn bur surfaces were performed after long-term use in a dental surgery. An Olympus SZ61 stereoscopic microscope and also a JEOL JSM-6610LV scanning electron microscope working with an Oxford EDS electron microprobe X-ray analyser were used for metallographic examinations. It was found that the studied dental instruments become damaged both during their use and during sterilization. The obtained results of the examinations showed that mainly the palatal bur, used to treat teeth on the palate side, was corroded. The working parts of the palatal burs were degraded through abrasion (edge rounding) and crumbling away of the diamond phase as well as by the occurrence of microcracks in the composite matrix, whereas the flame bur designed to prepare tooth tissues (flame-shaped bur with a safe end - the tip without a diamond coat), were degraded through bits of the diamond phase crumbling away, through microcrack formation between this phase and the matrix, and also by crumbling away of the matrix, as well as the flame bur designed to prepare tooth tissues (flame-shaped diamond bur) through the diamond phase breaking off.

The developed composite materials based on epoxy resins show high adhesion to concrete surfaces and good mechanical properties. Thermoplastic epoxy resins with various (380, 1830, 10 800) molecular weights and added polysulfide rubber can be used as coatings and glues. The epoxy composite with 10 800 molecular weight had better mechanical and adhesive properties than those of lower molecular weights. In this work the tensile strength, compressive strength, shear strength, tensile elongation and thermodynamic properties were studied. The materials for the compounds are called thermoplastics, which turn into a plastic state when heated and again solidify on cooling. Hot melt adhesives were first produced at the beginning of the 1950s and every year their production has increased. The new composite copolymer material, based on Bisphenol A, can be used as a thermoplastic composition for concretes, as well as a component or coating for various materials. Their use allows one to achieve high-speed mass production, where they significantly reduce the production time and labor intensity. In this article corrosion processes in concrete and reinforced concrete structures as well as their capability of preventing chemical degradation were examined. Composite materials based on epoxy resins have a great potential to solve this problem. Numerous materials have been developed and examined in the context of use for coatings in reinforced concrete structures. It should be noted that with protective coatings, the physical and mechanical strength of concrete structures increases to 50%, the chemical resistance is improved by several times, while water resistance is increased by 150%. This study also examined the technology for applying epoxy coatings on concrete and reinforced concrete surfaces. The study demonstrated that the coatings enhance the properties of reinforced concrete structures.

Hot melt copolyamide was mixed by the melt-blending process with 7 wt.% non-functionalized multi-walled carbon nanotubes and with amine modified multi-walled carbon nanotubes. The main goal of this work was to analyze the effect of functionalization of the properties of hot melt copolyamide. The rheological properties of the nanocomposites were examined by the dynamic oscillatory test using an oscillatory rheometer. Macrodispersion of both types of multi-walled carbon nanotubes within the copolyamide matrix was examined qualitatively by a light microscope and quantitatively using ImageJ Software. The thermal stability and characteristic temperatures such as the melting point and crystallization temperature were determined by thermogravimetric analysis and differential scanning calorimetry, respectively. It was found that the addition of 7 wt.% functionalized multi-walled carbon nanotubes increases the viscosity of copolyamide but to a lesser extent than in the case of non-functionalized multi-walled carbon nanotubes. Moreover, mixing copolyamide with amine functionalized multi--walled carbon nanotubes resulted in larger agglomerates which resulted in worse thermal stability than for non-modified multi-walled carbon nanotubes. Finally, the electrical conductivity measured by dielectric spectroscopy was lower in the case of nanocomposites with amine-functionalized multi-walled carbon nanotubes which indicates that the affinity to copolyamide was not improved by the amine groups.

Carbon fibre reinforced polymers (CFRPs) are an attractive construction material with an increasingly wide scope of application, including the aircraft industry. By combining them with metal elements and producing fibre metal laminates (FMLs), it is possible to achieve higher mechanical properties than in the case of combinations with glass fibre reinforced polymer (GFRP). However, there is a problem associated with galvanic corrosion regarding combinations with aluminium and its alloys, stainless steel and with magnesium alloys because CFRP composites are electrical conductors. Adhesives with increasingly higher resistivity are applied in adhesive bonding technology. Fibre metal laminates (FMLs), particularly those dedicated for aircraft primary structures must be not only corrosion resistant, but first of all they must be characterized by a proper combination of mechanical properties, including fatigue features. Therefore, when designing the metal surface treatment and the type of interlayers, it is necessary to consider the joint adhesion, mechanical properties of the hybrid laminate and corrosion properties. This article presents the characterization of an interface microstructure: the anodic layer on the AA 2024 aluminium alloy-GFRP-CFRP interlayer of hybrid laminates with electrical properties presented in a pre¬vious publication. The observations have been carried out on cross-sections of Al/GFRP-R/CFRP, Al/GFRP-S/CFRP and Al/CFRP laminates in a 2/1 layout with fibres oriented in the 0° direction. Moreover, impedance measurement was performed for the oxide layer in contact with a 3.5% aqueous NaCl solution by means of electrochemical impedance spectroscopy (EIS). It has been found that the low contact resistivity between the laminate with the GFRP-S interlayer was caused by carbon fibre migration to the Al/GFRP-S boundary. Furthermore, the low surface resistance of the CFRP composite and the porosity of the outer part of the oxide layer on aluminium enables the diffusion of aggressive ions and migration of electrical charge towards the metal substrate, which poses a threat of corrosion initiation in moisture condensation conditions.

The aim of the paper is to demonstrate and describe the fatigue failure mechanisms of eight-layer glass-epoxy composites with a central circular delamination, numerical description of the delamination problems and a possible optimal design. There are a few variables (tension and compression forces, number of cycles, construction of the tested plates) which can be changed during the experiment that will very likely provide different results. The problem is to find the link among all those variables to fully describe their influence on the physical behavior of the epoxy plate which is the subject of the experiment. The results are illustrated with the use of the numerical analysis method. Thanks to that, it is possible to describe how the number of cycles, tension force and stress variations affect the whole fatigue process.

The aim of this study was to examine the effect of different material combinations and process parameters on the material characteristics of sandwich structures. Therefore, the material properties of sandwich structures made from woven fabrics (glass/ flax fibers) and powder epoxy resin as well as balsa cores were investigated. These material combinations are highly interesting for customized lightweight constructions as they bear the potential to construct three-dimensional free shape structures. The structural set-up observed during this study consists of balsa wood which is covered with two outer layers of fiber reinforced epoxy resin. In order to compare the effects of these outer layers on the material behavior, specimens with woven fabrics made out of glass and flax fibers were manufactured. During a hot pressing process, the fiber bed was infiltrated with powder epoxy resin while being pressed to the balsa core. To determine the material characteristics of the manufactured composite, mechanical tests such as 4-point-bending (DIN 51227) and peel tests (DIN EN 1464) were executed. Further investigations consisted of microscopic analyses to ensure quality control of the specimens. Additionally, the degree of wood penetration was examined during this screening process. It was revealed that the specimens with glass face sheets yielded a higher flexural strength (average: 19.54 MPa) and modulus (1815.12 MPa) than the flax specimens (strength: 16.14 MPa; modulus: 1353.83 MPa). Furthermore, the average peel resistance of the glass specimens (1.54 N/mm) was slightly higher than the average value of the flax fabric specimens (1.38 N/mm). Concerning the infiltration behavior, greater penetration of the balsa core was noted when using glass face sheets. Keywords: glass epoxy composite, flax epoxy composite, woven fabrics, powder processing, balsa sandwich structure, material characterization

Lightning strike protection is one of the crucial structural demands for aircraft composites addressed to their integrity and durability after a strike. When the lightning strikes a classic composite structure, the generated heat from electrical resistance as well as mechanical impulse resulting from acoustic wave propagation, might cause serious damage. Currently used metallic meshes and foils immersed in composite structures are effective in dissipating lightning charges and generated heat, however, such a solution has numerous disadvantages like increasing mass, problems with adhesion on the metal/polymer interface, complicated manufacturing technology, etc. Therefore, a fully organic conductive composite was developed as an alternative to current solutions. After a lightning strike the developed composite should not only effectively conduct and dissipate the electrical charge and generated heat, but also stop burning, which appears due to very high temperature values in the vicinity of the strike area. In this study, flammability tests were performed for a classic carbon fabric-reinforced composite as well as for the developed conductive polymer and carbon fabric-reinforced composite based on this polymer for comparative purposes, with measurement of the combustion temperature. The obtained results show that the developed composite is characterized by sufficiently low flammability, however, further studies will be focused on further improvement of flame retardancy.

In the case of liquid phase processes used for the production of Al alloy matrix composites, the important factors are the interaction on the boundary of the liquid metal-ceramic phase, mainly the wetting of the ceramic surface. From this point of view, in the case of IPCs obtained by centrifugal infiltration, modification of the matrix alloy, the structure and physical properties of the porous ceramic materials, additionally the technological parameters like the temperature and time of infiltration as well as the rotational speed of the mould are important. In turn, the main parameters that influenced the efficiency of the infiltration process are the density, porosity, absorbability and permeability of the porous ceramic medium. The structural characteristics and physical properties of alumina foams, important for the infiltration of liquid aluminum alloy, have been presented. Scanning electron microscopy (SEM) and computer microtomography (μCT) were used to evaluate the microstructure of the Al₂O₃ foams. Selected properties of the foams such as density, open porosity, total porosity, absorbability were determined. In addition, the Ergun equation to determine the permeability of the foams was used. Metal-ceramic interpenetrating composites (IPCs) were obtained by the centrifugal infiltration of alumina foams with liquid Al alloy.

This article is devoted to interlaminar cracking research on carbon multidirectional fibrous-epoxy composites. Composite beams with 0°/0° 0°/45° and 0°/90° interfaces were subjected to double cantilever beam tests whereby force-crack opening displacement curves were determined. Additionally, crack length observations were conducted in order to determine the crack resistance curves of multidirectional composites. On the basis of the performed tests, it was found that the critical strain energy release rate for crack initiation is size independent of the material configuration. On the other hand, the fiber orientation is crucial to the critical strain energy release rate for crack propagation.

This paper presents the basic problems associated with the production of single polymer composite materials. The author has characterized the production of these materials and discussed the results of studies on the problems associated with manufacturing composites, that is the influence of the structure of the polymer material on the effect of moulding, as well as additives and the type of reinforcement fibres on its physical and chemical properties. The parameters of manufacturing single polymer polyester composites by the film-stacking method were determined empirically.

Fractographic examination of laminates reinforced with 2x2 twill fabric were carried out. Two reinforcement configurations relative to the global direction of delamination growth (GDDG) were considered: warp/weft tows parallel to the GDDG and warp and weft tows aligned at 45º with it. It was found that unlike for UD reinforcement, pure global Mode I and Mode II loadings resulted in local fractures typical for mixed mode I/II loading for both the global loading modes and reinforcement orientations. The possible reasons for such fractures were provided with the help of simplified qualitative stress analysis.

The paper presents the results of an experimental study concerning the strength of adhesive joints between the layers of a hybrid fiber metal laminate (FML) composite. The research was conducted on composites composed of aluminum 2024-T3 sheet metal and a glass fiber reinforced polymer (GFRP) prepreg made using the autoclave process. The key factor determining the quality of the layered composites is the high strength adhesive joint between the layers. The article discusses the issue of static inter-layer adhesive joint strength under different directions of loading for various types of adhesives. Shear strength tests for a single-lap joint were performed, as well as the peel strength test using the drum peel test. The strength tests were conducted for the variant that had an inter-layer joint made by epoxy included in the prepreg, while the second variant used an additional layer of adhesive film. The surfaces of the metal layers were prepared in accordance with the methodology used in aerospace production processes. The sheet surfaces were anodized in a sulfuric acid solution and then primed. Surface structure measurements of the sheets were made immediately before the joining process. Each layer was assembled in a clean room. The strength tests of the adhesive joints were conducted in static shearing and peeling conditions at room temperature. The results show that under shear loading the adhesive film lowers the elastic module of the joint and results in a slight increase in strength. However, under normal loading, there was 289.4% increase in the peel strength of the joint with the adhesive film. After the strength tests the surfaces of the destroyed adherends were analyzed using SEM. For the shear strength specimens no significant differences were found, whereas for the specimens subjected to peeling it was shown that cohesive damage was observed for the variant with the adhesive film, while the specimens without adhesive film were characterized by adhesive damage.

A new method of numerical homogenization for functionally graded composites (FGCs) was proposed in the paper. It was based on the method in which the gradient heterogeneous microstructure is divided into homogeneous slices. In the presented research, the model was built using 2D elements, with two linear material models of Young modulus E = 50 MPa and 750 MPa distributed in the sample volume in accordance with linear and normal graduation. The numerical homogenization was carried out by dividing the heterogeneous sample into 4, 5 and 8 slices. The substitute material characteristics were calculated and implemented into the sliced model. The numerical compression test results of the sliced and heterogeneous models were compared and the method error was calculated. The conclusion was that the more slices applied, the more exact results will be received. Selection of the number of slices should be based on the accuracy that is necessary for the global model to reflect the gradient properties of the structure and on the available computational capacity. A disadvantage of this modeling approach is the loss of ability to evaluate the distribution of stresses around the grains of individual phases in the microstructure.

BADANIA WPŁYWU MONTMORYLONITU NA WYBRANE WŁAŚCIWOŚCI I STRUKTURĘ The paper discusses the results of examinations of mechanical properties and examinations of the structure of composite polybutylene terephthalate with montmorillonite. The aim of the material examinations presented in this paper was to determine the effect of the content of the fillers on the structure and properties of the polymer composite. For this purpose, the examinations of tensile strength, hardness and topography of sample surface were performed for the surface of the specimens of the composite obtained using atomic-force microscope. The specimens of composites were obtained using the injection moulding method with processing parameters for which the best properties were obtained. The study revealed an insignificant increase in tensile strength for the specimens with addition of montmorillonite of 3 and 7% from 51 MPa for butylene polyterephthalate to 53 and 54 MPa, respectively. An increase in material Shore hardness was also found. All the composite specimens were characterized by hardness at similar level of 95 to 96 degrees on the Shore scale. An increase in hardness of the composites measured by means of the ball indentation test was observed compared to polybutylene terephthalate. Addition of montmorillonite of 3 and 7% leads to the increase in hardness from 130 MPa for polybutylene terephthalate to 143 and 148 MPa, respectively. Structural changes caused by the use of montmorillonite as a filler were observed in the examinations of surface topography. Several structural drawbacks linked to the adhesion between the matrix and the filler were also found.

Preliminary comparative static identification experimental tests on four selected commercial auxetic woven fabrics were conducted in terms of the tensile test in the auxetic fibre direction. A new method of such tests was developed, based on capstan grips as well as on video-extensometer and extensometer techniques. The identification tests were carried out at temperatures of 20 and 180°C due to the intended use of auxetic fabric as a protective curtain against a shock wave induced by a gas explosion. The ultimate tension force per unit width of fabric, effective Poisson’s ratios in the fabric plane and in the transverse plane, as well as the absorbed energy were determined approximately. The auxetic fabric with the relatively best properties was selected.

The issue of energy absorption during impact is present in various aspects of life. The possibility of dissipating unwanted energy gives huge opportunities for a variety applications such as helmets, car bumpers, smart body armours and protective pads. Nevertheless, there are numerous technical problems with achieving a compromise between good energy absorption efficiency and other important properties such as flexibility, weight and thickness. The article describes a study of composite structures based on shear thickening fluids (STF) and auxetic foams. The composites are developed as a potential component of products with high energy absorbing efficiency. The study reports on the rheological behavior of STF and force absorbing properties of the manufactured composites. In the experiment, two types of STF and eleven types of auxetic foams were used. Force absorbing tests for the produced samples were performed by dropping an impactor with the energy of 5 J. It was proved that the addition of STF to the auxetic foams increases the force absorbing efficiency.

In refining treatments (removal of solid inclusions) related to cast aluminum alloys as well as the recycling of cast metal composite material [MMK] on the matrix of aluminum and its alloys, consisting in separation of the components, substances which form another liquid phase (aside from the liquid metal (alloy)) are used. With regard to aluminum alloys, these substances are both refining fluxes and so-called recycling centers. They are composed of molten salt mixtures (mainly chlorides and fluorides). The effectiveness of their action is determined by the value of interphase tensions on the boundary with a liquid metal (alloy), which should be as small as possible. The values of interphase tensions in such system are not very well known, which led to an attempt to specify them in greater detail. A measuring station intended to specify them by means of the so-called ring test was constructed. The principle of conducting such measurements is simple but the method of their performance is difficult due to the specific properties of biphasic systems at significantly elevated temperatures. To complete the test stand (facility), a laboratory resistance crucible furnace was used and a measurement system composed of a probe that cyclically crosses the interphase boundary, the probe drive mechanism and a force gauge that continuously registers the changes in the values of forces acting on the probe. A non-standard massive cast iron crucible with a considerable thermal inertia was placed in the furnace chamber. The metal input (aluminum alloy) and salt mixtures (being refining means or recycling centers) were melted in this crucible. Trials were carried out using fixed values of the probe dimensions, speed of the probe crossing the interphase surface and frequency of registering the force gauge indications. During each series of trials, changes in the temperature values of the tested systems were recorded. It was found that both the method of measuring interphase tensions and the method of its realization performed well, ensuring reliable and reproducible results. The only drawback was the material of the probes used. The stainless steel used to make them proved to have poor resistance to the operating conditions. Despite this, the method and way of determining the interphase tension values in the systems allowed successful realization of the intended research objectives.

The desire to obtain unique properties of polymer materials and the ever growing competition in the plastics market have a direct impact on the intensification of research in materials science. This article regards innovative proposals to modify polymeric material (epoxy resin) to obtain new products (composites) with improved properties. The mechanical and chemical properties of composite materials based on epoxy resins modified with synthetic polysulfide rubber were determined. Moreover the effect of adding industrial waste (glass powder) on the structure and performance of the composites was estimated. The physical and mechanical properties of the composites as well as their chemical resistance to aggressive environments were determined. One of the applications for the innovative composite materials is to use them as a protective material, e.g. in construction for lightweight concrete.

This paper describes the changes in the tribotechnical properties of CuSn10 sintered bronze and MMCs based on this bronze reinforced with ultrafine composite Al-based powders. It was observed that the presence of hard particulates in the MMCs leads to a decrease in the friction coefficient and, particularly, wear rate. The presence of Al-based particulates in the MMC reduces the wear rate considerably. It decreases in the direction of FeAl → NiAl → Ti-Al-Cr particulates and for the best MMC composition the gain is about 20 times. In the MMC wear process, micro-craters are formed on the contact surface and it is the principal reason for the decrease in the wear rate.

A method was developed to manufacture Al-Si alloy matrix composites reinforced with MAX phases by squeeze casting pressure infiltration of porous preforms. The MAX phases were synthesized using self-propagating high-temperature synthesis (SHS) in the microwave assisted mode. For the produced composites abrasive wear resistance tests were carried out using the pin-on-flat method with reciprocating motion for different load values (0.1, 0.2 and 0.5 MPa), while maintaining other parameters (sliding distance, speed) constant. The sliding distance equaled 2000 m with the average speed of 0.3 m/s, whereas the flat counterpart was made of CT70 tool steel with the hardness of 67 HRC and roughness Ra = 0.4÷0.6. Before testing both of the tribosurfaces were degreased with acetone. Volumetric sample consumption was investigated and changes in the structure of the working surfaces were analyzed. Optical and scanning electron microscopy analysis were also performed and elaborated in order to facilitate understanding and interpretation of the wear mechanisms. It was confirmed that the composite materials exhibit more than two times higher wear resistance than that of the matrix itself. The wear rate of the matrix falls within the range of 3.5÷5.5-10⁻⁴ mm³/Nm, while for the composite material - 1.3÷2.4-10⁻⁴ mm³/Nm. In the Al-Si matrix the main wear mechanism was identified to be based on plastic deformation composed of scaling and cracking processes, while for the MAX phase composite it is principally abrasive wear leading to pre-fracture, delamination and extraction of MAX phase platelets.

Fiber reinforced polymer composites and aluminum alloys nowadays constitute the most dominant materials applied in the aerospace industry. This paper gives the theoretical background and provides both analytical and numerical calculations for analysis of the elastic-plastic behavior of a selected fiber metal laminate. The work introduces the closed-form solution for a multi-layered structure subjected to a unidirectional loading/unloading cycle, and explains the process of stress and strains development. GLARE^® plates, which are exposed to a tensile load, can generate even higher stress in the aluminum layers at unloading. Moreover, delamination and buckling of the external layers can be expected. The paper gives a detailed theoretical framework for this behavior based on the plasticity theory, provides numerical calculations, and compares them with the FEM and experimental results. Keywords: elastic-plastic behavior, thin-walled plates, composite-reinforced metal structures, theory of orthotropic materials, GLARE^®

In this study prediction of the strength properties of composites made of polyester resin and continuous glass fiber reinforcement in established grades was performed. Structure modeling based on the numerical homogenization method was conducted using Digimat FE commercial code, taking into account the geometry and properties of all the composite components. In the first stage, analysis was performed for OCF M8610 mat. At the beginning the calculations were done for beam roving from S glass. Preliminary calculations were performed for the virtual composition of glass fibers-air, which allowed calculation of the yarn properties, directly used to build the glass mat model. The second stage of the calculation was carried out for glass mat saturated with polyester resin. For this purpose, roving bundle data and polymer matrix data were implemented. The volume fraction of the glass mat in the composite was also determined, and a random fiber orientation in the plane was defined. The properties of the fabric-resin composite were calculated for polyester resin and Cofab A1118B glass fiber plain weave fabric. The basic properties of the fiber in the analyzed bi-directional fabric were established on the basis of literature. The calculation of some fabric properties was conducted by a different algorithm than in the case of the mat. The last stage of property calculation for the warp and weft was to predict the weave properties based on the manufacturer's data. Only at this stage was the mean field method (MFM) used in the calculations. The geometrical dimensions of the reinforcements were calculated including its grammage, where the value is highly compatible with the grammage given in the literature. For both types of reinforcement visualization of the composite structure was performed. The calculated composite properties were used in strength simulations of a useful product for three variants of composite reinforcement: (a) polyester resin without reinforcement, (b) polyester resin with glass fiber mat, (c) polyester resin with glass fiber fabric, which allowed carrying out a comparative strength analysis.

The aim of this paper was to characterize the microstructure and selected properties of Ni-3YSZ composites. The composites were prepared from a powder mixture containing 90 vol.% ZrO₂ and 10 vol.% nickel powder. In the experiments the following powders were used: ZrO₂ powder stabilized by 3 mol% Y₂O₃ from TOSOH ZIRCONIA 3YSZ of an average particle size less than 100 nm and density 6.05 g/cm³ and Ni powder from Sigma-Aldrich of an average particle size 1.5 µm and density 8.9 g/cm³. The samples were formed by uniaxial pressing. Two series of samples were fabricated with different sintering temperatures: series I was sintered at 1400°C and series II was sintered at 1600°C. The sintering process was conducted in an argon atmosphere. The structure of the samples was examined by X-ray diffraction (XRD) after sintering. The microstructure of the composites was investigated by scanning electron microscopy (SEM). The chemical composition was examined by energy-dispersive X-ray spectroscopy (EDS). The selected physical properties of the prepared composites was measured by the Archimedes method. The hardness was measured using Vickers hardness testing. Based on the hardness measurements the KIC values were determined. Uniaxial pressing and the sintering method enabled the manufacture of Ni-3YSZ composites. The microstructure observation revealed homogeneous distribution of the Ni particles in the ZrO₂ matrix in both series. The XRD patterns of the composites after sintering at 1400°C (series I) and 1600°C (series II) show that the composites consisted of three phases: t-ZrO₂, m-ZrO₂ and Ni. It was found that the temperature of 1400°C is not sufficient to obtain Ni-3YSZ composites with a high relative density.

The aim of this work was to determine the influence of thermal pretreatment of thermoset semi-finished products on the thermal properties as well as the subsequent processing parameters. For this purpose, the curing behavior in the pretreatment of thermoset fiber reinforced semi-finished products was analyzed. A semi-finished product with glass fiber reinforcement and powder resin system A.S.SET 1010 was investigated. During processing of the rigid semi-finished products, melting-up of the matrix system is necessary before shaping. To determine the influence of this process, samples were pretreated and tested at different heating temperatures and times. The change in the glass transition temperature and the degree of cross-linking was determined using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Thanks to this, the curing behavior and thermal properties of the semi-finished products were evaluated during their pretreatment depending on the heating temperature and time. It was confirmed that the pretreatment has a major influence on the degree of cross-linking, glass transition temperature as well as the later processing parameters.

The paper presents the characteristics of the ZrO₂-Ti composite system, formed by the slip casting method. Samples were prepared from slurries with a 45 vol.% solid phase content and 0, 3 and 10 vol.% additions of titanium, respectively. The sintering process was executed in the inert atmosphere of argon at 1450°C with a 2-hour dwell time at the maximum temperature. Density and strength measurements of the green bodies and sintered samples were made. In order to determine the phase structures before and after the sintering process, X-ray analysis was conducted. Vickers hardness and fracture toughness for the sinters were measured. The addition of titanium particles to ZrO₂ resulted in a slight decrease in hardness compared to the plain zirconia samples, while the fracture toughness of the composite samples increased. The tensile strength of the green bodies and sinters was at a similar level for the zirconia and composite samples. For the green bodies, the monoclinic ZrO₂ phase and tetragonal ZrO₂ were revealed. After sintering, only the tetragonal phase of zirconia was detected.

The self-heating effect occurring during the cyclic loading of polymers and polymeric composites may initiate accelerated thermally induced fatigue processes, which causes a rapid increase in the self-heating temperature at a location of stress concentration and, as a consequence, sudden structural degradation. Therefore, it is essential to investigate this process and determine the criticality of the self-heating effect, i.e. the critical value of temperature which initiates accelerated degradation processes. In this paper, an aspect of microcrack formation and development was considered as an indicator which reflects the degradation degree of a structure. Microscopic observation of microcrack development at progressive temperature values was chosen due to its high sensitivity to the initiation of fracture processes among applied measurement techniques to evaluate structural degradation during fatigue tests. Appropriate image processing techniques as well as quantitative measures to describe microcrack development enable evaluation of the criticality of the self-heating effect using this approach and comparison of the obtained results with those obtained by other measurement techniques. The specified critical value of self-heating temperature allows determination of a safe temperature range for heavily loaded structures made of polymeric composites, which can be helpful both during the design stage as well as at the operating stage of composite structures.

Ceramic failure, at stresses lower than those when K_Ic is reached, might be an effect of subcritical crack propagation.It occurs when the material is in service in the presence of water (even water vapour) for a long time. If this phenomenon leads to limiting its useful life, it is important to predict the lifetime of a ceramic component under specific conditions. Dynamic tests are suitable to determine subcritical crack growth parameters. Calculations are made to determine material behaviour under static loading on the basis of strength data. The paper presents the results for zirconia-alumina composites with 5, 15 and 50 vol.% inclusions to compare materials with different types of microstructures. Pure zirconia sintered bodies were used as the reference material.

The numerical modelling and simulation of approval tests of a side safety device (anti-bicycle buffer) for Wielton trucks was developed. The new type of device is made of glass-reinforced polyester laminates, manufactured using press technology. As part of the design, simulation of approval tests of the new design solution was conducted for five variants of the composite shells using MSC.Marc finite element code. The results are presented in the form of deflection contour maps and equivalent effort index contour maps for the laminate shells. The load capacity and usability conditions with respect to the buffer were checked. It was shown that all the analysed options of the GFRP composite buffer fulfil the approval conditions. The buffer case, optimal in respect to structural materials and formation technology, was recommended for production. The simulation results of the approval tests on the deflections of the side safety device chosen for production were compared with the results of the experimental approval tests. Good qualitative and quantitative agreement of the results was observed.

The paper presents the influence of the reinforcing phase form on the structure and tribological properties of composites with an aluminum alloy (AlMg5) matrix containing glassy carbon as a solid lubricant. These composites are designed to produce cylinder liners of piston machines, namely air compressors, combustion engines and pneumatic actuator cylinders. The results of comparative examination of composites containing foam inserts made of Al₂O₃ coated with glassy carbon and composites containing foam inserts made from glassy carbon are presented. Adding Al₂O₃ foam to the AlMg5 alloy increases the compressive strength, but enhances the friction and wear of the sliding cast iron. The wear of the composite containing Al₂O₃ when rubbing against a pin made of cast iron GJL-250 is more than twice lower than the matrix. The presence of glassy carbon foam reduces the friction and wear of both the cast iron pin (more than five times) and the matrix. The presence of the Al₂O₃ foam in the AlMg5 alloy deteriorates the heat dissipation, causing an increase in temperature in the friction zone during friction in air against GJL-250 cast iron. The temperature in the friction zone of the composite with Al₂O₃ foam is more than 20°C higher than the friction zone of the composite comprising glassy carbon foam.

The presented paper is devoted to the task of computational simulation of ferromagnetic particles in magneto-rheological fluids. Under the action of an external magnetic field, ferromagnetic particles form a complex internal microstructure. This microstructure is generally parallel to the direction of the external magnetic field intensity vector. The main aim of this work is to investigate the influence of the short-range repulsion interactions between the particles on the final shape of the internal microstructure. This interaction is implemented in the simulation process in such a way that the moving particles do not overlap. In the adopted theoretical model, in addition to the effects of short-range repulsion interactions, magnetostatic and hydrodynamic interactions are also taken into account. It is worth stressing that the applied theoretical model is very simple, however, it enables estimation of the mentioned effect. It was assumed that all the ferromagnetic particles have a spherical shape with a constant radius. A series of two-dimensional numerical simulations is carried out based on the molecular dynamic algorithm. The short-range repulsive interactions are described by a polynomial and by an exponential function with various parameter values. It turned out that the final shape of the microstructure strongly depends on the applied form of short-range repulsion. It is possible to obtain single isolated strings of particles as well as complex structures known as particle clusters.

The paper presents the influence of gypsum mold porosity as one of the process parameters allowing change in the gradient microstructure of composites obtained by centrifugal slip casting (CSC). This method combines the effects of slip casting and centrifugation. Composites made by centrifugal slip casting have the shape of hollow cylinders. Three types of gypsum molds with different porosity were used in the experiment. Alumina matrix graded composites with nickel particles were investigated. Slurries with a 45 vol.% solid content were consolidated using centrifugation at 1700 rpm. The composite properties were characterized using X-ray diffraction and scanning electron microscopy. Selected physical properties of the sintered specimens were measured by the Archimedes method. Applying a reductive atmosphere (H₂/N₂) during sintering averted the formation of NiAl₂O₄. The research showed that the use of different gypsum molds has an influence on the microstructure of Al₂O₃-Ni composites. The presented results revealed that with an increase in gypsum mold porosity, the width of the zone with nickel particles in the composites increases. It was found that the maximum width of the zone with the metal particles was obtained by the composites produced using the gypsum mold with the highest porosity.

Glassy carbon foams were produced by the pyrolysis process using polyurethane foam with a layer of phenolformaldehyde resin as the precursor. The pyrolysis process was conducted in vacuum conditions at 1000°C. The pyrolysis conditions were determined on the basis of carried out thermogravimetric analysis. The basic mechanical properties like the compressive strength of the carbon foams was measured and compared with the theoretical value. Furthermore, the glassy carbon foams were applied as skeleton reinforcement in epoxy resin matrix composites. Analysis of the mechanical properties revealed that the values of hardness and compressive strength of materials with spatial carbon foam are almost two times higher than for a pure matrix applied as the reference material. The major factors that influenced the final mechanical properties are the quality of the obtained foams and the amount of carbon in the material volume. Moreover, it was proved that the application of carbon foam with low mechanical properties led to significant increases in the compressive strength of the composite materials.

The paper presents a flexural strength comparison of hybrid epoxy composites with different reinforcing phases and amounts of used fillers. As the reinforcement, carbon fiber was used in mat and fabric forms. As the matrix, an epoxy resin and a mixture of the epoxy resin with a filler in the form of coal fly ash was used. The samples were produced according to the PN-EN ISO 178 standard and bending stress values of the studied composites were determined. The work is a part of studies related to selecting material for the hull of an innovative yacht with a hybrid drive, fueled by renewable energy sources, in the scope of the “RepSail” project in the “Era Net Future Travelling” contest realized at the Maritime University of Szczecin.

In this study an effort was made to form a composite microstructure in the surface layer of the AlZn5.5MgCu aluminium alloy using FSP technology by introducing SiC particles to the alloy. In the experiment the multi-chamber solution was used, which consists in placing SiC powder in chambers separated one from another, cut into the modified material, perpendicular to the sample surface. To perform the friction stir processing a tool with a threaded pin was used. Evaluation of the surface treatment effects was carried out by means of both light and scanning electron microscopy. In addition EDS analysis was performed as well as a comparative measurement of hardness. The conducted examinations showed strong refinement of the of aluminium alloy structure and intense dispersion of the SiC particles in the surface layer of the material, resulting in the formation of a metal-ceramics type composite microstructure. The presence of SiC particles was found in both the stirred zone (SZ) and the thermo-mechanically affected zone (TMAZ). The consequence of the strong refinement of the microstructure and the introduction of SiC particles was a considerable increase in the hardness of the surface layer of the modified material. The performed experiment showed the effectiveness of the applied multi-chamber technology and the possibility to create a composite microstructure in the surface layer of the AlZn5.5MgCu aluminium alloy.

Silver matrix composites containing 1÷2% graphene platelets of various thicknesses were uniaxially hot pressed at 480°C in vacuum from powders ball milled for 5 hours. Two kinds of graphene nanoplatelets were added: (i) - nanoflakes (FLRGO) of a thickness 2÷4 nm, which led to a higher hardness (35÷49 HV) and slightly lower electrical resistivity of the composites, than that of pure hot pressed Ag and (ii) - nanographite platelets (N006) 10÷20 nm thick as confirmed by electron microscopy, which caused a similar increase in hardness up to 34÷45 HV and about a 40% higher electrical resistivity than that of pure hot pressed Ag. SEM studies showed a more homogeneous microstructure of the composites with the FLRGO graphene additions. TEM studies confirmed refinement of the thickness and lateral size of the graphene particles after milling and hot compaction down to a few nm manifested by diffused electron diffraction. The hot extrusion of hot pressed composites with FLRGO platelets caused the growth of graphene platelets and coagulation of the platelets, which contributed to a higher hardness and electrical resistivity.

The paper presents the structure and the influence of the chemical composition and structure on the insulating properties of a polymer-ceramic microspheres hybrid composite used as insulating materials in infrastructure of transport and means of transport. The composite matrix is an acrylic resin and ceramic microspheres with the pressure of 13 Pa are the reinforcement. A content of about 44 microspheres in a 1 mm-thick coating has a major impact on the thermal insulating properties of the coating. The coefficient of heat conduction depends from the temperature and is lower at lower temperatures. This is the reason why these coatings are used as an insulator in technical means of transport requiring cooling (refrigerators and ice vehicles) and in the aviation industry to protect the interior of the plane against low temperatures during flights at high altitudes. Microscopic examinations were performed, the stereological features of the coating were examined and a equivalent model of the resistance of thermal transmittance through the coating have was developed. The equivalent coefficient of thermal conductivity of the composite, calculated on the basis of a formula taking into account the volume shares of the components and their thermal properties, is greater than the coefficient of ceramic spheres with their volume fraction amounting to 80%. This is caused by the fact that the formula does not take into account the stereological properties of spheres in the composite, i.e. the distribution pattern and number per unit of thickness of the coating.

A wide range of non-contact measurement methods is used in many fields of industry. 3D scanning technology is one of the modern techniques of geometry registration for reverse engineering, inspection or structure deformation analysis. The aim of the study is a comparative evaluation of square composites plates with holes under compression loading. The evaluation was performed on the basis of results from hand-held 3D laser scanner measurements. An essential element of the presented evaluation is analysis of the wall thickness of the plates. The range of this paper covers: presentation of 3D laser scanning measurement methodology, experimental tests and 3D scanning comparative evaluation of the specimens. The geometry of the composite plates with two kinds of holes: elliptical and cylindrical are compared. Higher values of wall thickness deformations for the plates with the elliptical holes were observed.

Hybrid materials such as Fibre Metal Laminates (FMLs) containing carbon fibre reinforced polymers (CFRPs) are very attractive candidates for novel design strategies due to their specific properties. However, Fibre Metal Laminates (FMLs) may be susceptible to galvanic and electrochemical corrosion in a damp environment due to the applied metal sheets. Aluminium alloy-glass/epoxy composite FMLs exhibit high corrosion resistance. Their corrosion process is limited to the metal outer layers if they are not protected because glass fibre reinforced composites are non-conductive. Galvanic corrosion initiation is likely when a composite contains carbon fibres, owing to the electric conductivity of these fibres. Therefore, it is necessary to determine the electrical properties of the produced hybrid materials. Measurements were made to determine the surface resistivity of components and contact resistivity of the laminates. Investigations were conducted on on a polymer composite and FMLs consisting of aluminium 2024-T3 joined with GFRPs (R-glass, S-glass) and CFRP. The aluminium alloy sheet was anodized in a sulphuric acid solution (SAA process). The composite plates and hybrid laminates were cured in the autoclave process. The surface resistance of the materials was determined by measuring the drop in current using the two probe method and strip electrodes. In the laminate specimens, the electrodes were placed in the longitudinal direction between the corresponding layers. The interlaminar interface properties of these laminates were studied by measuring the contact electrical resistivity of this interface. Moreover, the variation in temperature with time during electrical measurements was recorded by means of the thermovision technique for the composite specimens. This study revealed that the aluminium oxide and GFRP-R composite are insulators with very high but negative surface resistivity. The surface resistivity of the CFRP composite is equal to about 102÷103Ω/ı and depends on the direction of the fibres. When the electrodes are located perpendicularly to the fibres, the surface resistivity is lower and the surface temperature increases locally. Generally the contact resistivity of this composite is ~103 times higher than indicated in literature. It is a result of the high quality of the prepreg and autoclave curing of the laminate. The measurements of electrical contact resistivity indicated that it is possible to obtain a dielectric interface between the aluminium alloy and carbon reinforced composite by anodizing the aluminium and applying aglass prepreg layer 0.25 mm thick. The thinner glass composite layer does not increase the in-plane contact resistivity.

The subject of the studies was the assessment of polypropylene utilization possibilities by using shredded polypropylene as a mortar component. The article presents the research results of the impact of shredded polypropylene on selected properties of the cement composite. The assessed material was cement mortar, the composition of which included an additive - a polymer plastic in the quantity of up to 2%. The scope of the studies included assessing the impact of the polymer plastic waste on the obtained properties of the cement composite and in particular, changes in the compression and bending strength, absorbability and capillary rise of water. The studies were meant to assess the possibilities of using additives originating from polypropylene production waste and to indicate the direction for further studies on cement composites.

One of the basic methods for joining composites are adhesive joints. In contrast to traditional methods used in connecting metal structures (bolting, riveting), bonding ensures uniform stress distribution. Bonding requires appropriate technological conditions and proper surface preparation. In the case of bonding composites, surface preparation methods are based on mechanical processing. The authors conducted a study to compare the different methods of surface preparation used in the adhesive bonding of composites. As a parameter defining the efficiency of the method, stress failure in a tensile test was used. Specimens were made based on the ASTM-D1002 standard using a carbon-epoxy prepreg and DP-490 3M adhesive. The article contains the results of tensile tests for three types of surface treatment.

A simplified procedure for determining effective ultimate stress that could account for the adverse effects of undetected damage done to laminates was described. The procedure was based on the assumptions that an equivalent open hole (EOH existed that could appropriately represent the extent of damage for the purpose of calculating strength and that the laminate under consideration was notch sensitive. Particular emphasis was placed on the assessment of BVID extent, which was crucial to define the EOH dimensions. The results of different inspection methods concerning the damage extent were presented and compared with each other. Moreover, it was experimentally shown that for a typical inspection condition the detectability threshold of BVID expressed in terms of indentation depth, δ
, and was 262 µm. It was found that the extent of damage defined based on visual inspection was significantly different from that defined based on C-scans and fractographic inspections. It was concluded that to determine the EOH dimensions, the damage measurements were not sufficient while definition of the EOH dimensions could be based on the equal values of the stress concentration factor caused by the damage of a given extent and EOH.

The article presents the results of the properties of sound absorbing layer systems produced from recycled polyurethane foams. The sound absorption coefficient values were determined on the basis of the standing waves method in the frequency range from 1000 to 6300 Hz. The average sound absorption coefficient values for the systems produced from the polyurethane foams were
α_f = 0.82 (system formed from a foam of an apparent density of 220 kg/m³), α
_f = 0.59 (system formed from a foam of an apparent density of 240 kg/m³). A comparative of the sound absorption coefficient values of produced chips layered in comparison to single layer foam was also presented. The highest average sound absorption coefficient value was obtained forthe layer system formed from a foam of an apparent density 220 kg/m³. The conducted study of the properties of sound absorbing polyurethane foam allowed selection of a technical solution that can be used to reduce noise in the work environment, and also to expand the possibilities of practical application of polyurethane foams from PU recyclates.

In recent years dynamic progress has been seen in almost all areas of engineering materials. It has contributed to the development of new, innovative materials such as composite materials. Nowadays, a great deal of research is focused on ceramic/metal composites due to their potential to be used in many applications. An example of such a material is ZrO₂-Ni composites. This paper describes ZrO₂-Ni composites formed by uniaxial pressing and sintering in an argon atmosphere. The microstructure, selected physical and mechanical properties such as hardness, fracture toughness and the biaxial strength of the composites were investigated. The sintered composites had a relative density close to 99% of the theoretical density. The distribution of the component phases was uniform. It was found that the presence of Ni particles affects the mechanical properties of the ZrO₂ matrix. It was also revealed that the composites exhibit a lower bending strength than ceramic materials obtained under the same conditions. The composites show a decrease in hardness in regard to the hardness of monolithic ZrO₂. The presence of Ni particles in the composites causes dissipation of propagating crack energy, which results in an increased fracture toughness value measured for ZrO₂-Ni composites in comparison to the value obtained for monolithic zirconia.

Sandwich composites are very popular nowadays due to their beneficial mechanical parameters and low weight. The aim of the paper was to investigate the failure mechanisms of different sandwich structures under shear stresses. Composites consisting of carbon laminate skins and cores with different geometry were tested. The core materials included various expanded polymer foams, balsa wood and honeycomb structures - aramid and cellulose. These material combinations enabled the authors to compare the specific shear strength and fracture energy of different sandwich structures, describe the factors which influence the behavior of materials under shear tension, and characterize the failure mechanisms. Sandwich composites were manufactured by two methods: the one-step method in which carbon fabric was laminated directly onto the core, and by the two-step method. The faces made employing the first method failed to meet the appropriate strength criteria, therefore the second method was used. In the first step, faces made of four layers of carbon fabric and epoxy resin were pre-manufactured by hand lay-up. After crosslinking, the faces were glued to the core and left in higher pressure conditions. Samples were cut to the required dimensions. Shear strength was tested by three point bending of a short beam. The method is simple and allows shear stresses to dominate in the sample. Tests were made on a testing machine, Zwick 1435. The density of the samples was considered as well, so as to compare their specific strength. The highest value of specific shear strength, (8.7 ±0.7)·10³ Nm/kg, was demonstrated by the composite with balsa, whereas for the composite with the honeycomb it reached (3.3 ±0.3)·10³ Nm/kg and for samples with foams (4.2 ±0.2)·10³ Nm/kg. Additionally the failure energy was calculated for each material. The composite with aramid honeycomb had the highest value - it reached (9.3 ±0.5) kJ/m², while value of this parameter for balsa was the lowest: (3.3 ±0.3) kJ/m². The composite with balsa deformed elastically until break point and a crack between the layers appeared. The sandwich structure with the aramid honeycomb core is a promising material as it exhibited a multi-stage failure mechanism. Firstly, it deformed elastically, then the cells collapsed. Only in the composite with balsa and honeycomb with four-layer skins was shear the dominant failure mechanism. The composites with isotropic foams did not fulfill expectations, they deformed plastically and a notch appeared. That is why they need further examinations to increase their shear strength. In this study, the cracking mechanisms of the composites were evaluated based on microscopic observations using a digital microscope. Depending on the core geometry, the following mechanisms were identified: core shear for the honeycomb, delamination and crack for balsa, and notch appearance for the foam composites. The presented results are an introduction to further investigations of sandwich failure under different conditions.

The paper presents an assessment of the filler percentage impact on the stress-strain characteristics of wood-polymer composite (WPC) samples loaded in a uniaxial tensile test. The analysis was based on both experimental studies as well as numerical simulations. The manufactured composite consisted of polypropylene as the polymer matrix and wood fiber (WF) of varying percentages, i.e. 10÷40%. Numerical modeling of the static tensile test was performed using Ansys commercial code taking into account the heterogeneous composite structure and fibers orientation. In order to define the heterogeneous material, Digimat software was used. Appropriate calculations were made using the Mori-Tanaka homogenization model.

Nowadays, the propagation of elastic waves, particularly Lamb waves, is very often used in detecting damages in different kinds of composite materials. These systems are known as structural health monitoring (SHM). However, the phenomenon of Lamb wave propagation is very complex, especially in the case of thin-walled composite structures. Generally, three types of Lamb waves are observed, namely: longitudinal or pressure waves (L), shear vertical (SV) and shear horizontal (SH). The phase and group velocities of the mentioned waves depend on the thickness of the structure and the frequency of the excited signal. This fact makes proper interpretation of the received dynamic response of the structure difficult or even impossible. Therefore, determining the appropriate dispersion curves for different materials is a very important issue. In the present review, the most commonly used analytical approaches for determining dispersion curves in the case of multilayered composite plates are presented. At the very beginning of this work the solution for single isotropic plates is presented. Next, the fundamental assumptions of the theoretical model, which describe the elastic wave propagation phenomenon in multilayered materials, are discussed. In the first part, the relationships describing the elastic wave propagation for single orthotropic lamina are presented. There are two studied cases: namely when the wave front of the elastic wave travels along the principal directions of the material and when the wave front of the elastic wave travels in any arbitrary direction.

The appearing process-induced stresses influence the mechanical performance of a composite structure and can initiate pre-load damage. Residual stresses evaluation is particularly important in multilayered composites where the ply orientations and stacking sequences highly influence the appearing stresses. Various numerical methods are used to simulate the growth and development of arising residual stresses. The general aim of the current work is to present the fundamental relations to predict the strains and stresses during the manufacture of laminated composites. Additionally, different modeling techniques and constitutive models are presented with the intention of understanding the different phenomena taking place during processing and which models best predict the process effects. As an example, a simple finite element model of a thermally loaded laminate is proposed to present the heterogeneities in through-thickness residual stresses distribution.

In this work, a brief review of various approaches using Infrared Thermography (IRT) as a non-destructive method applied for better understanding of fatigue behaviour and the damage process is presented. Rapid determination of fatigue limits obtained with the use of IRT is in very good agreement with the conventional experimental testing program for a wide range of materials including various types of composites. In addition, it creates the possibility of locating, evaluating and monitoring fatigue damages both within standard specimens and structural components. Despite these achievements, there is little work concerning the use of IRT in the analysis of curved composite structures with delaminations subjected both to static and/or fatigue loads. In this paper, stepwise methodology, how composite curved panels can be incrementally tested in order to characterize and control real damages occurring during static loads is presented with emphasis on the possibility of using it for fatigue tests. It was shown that artificial delamination does not propagate in contrast to real defects which can be monitored by active thermography tests after each load step. The presence and evolution of damages caused by static loads has a great impact on the thermal behaviour of the curved composite panel and can be observed by changes in the temperature contrast on the investigated surfaces. Future works will concern application of the proposed methodology with the use of Active Infrared Thermography (AIRT) in the quantification of failures occurring during fatigue testing of curved composite elements.

In the first part of the current review, the fundamental assumptions of the theoretical model of elastic waves propagation in multilayered composite material are presented. Next, the equations which describe elastic wave motion in the case of single orthotropic lamina are derived. In the second part of this work, the most commonly used method of determining dispersion curves for multilayered composite material are discussed, namely: the transfer matrix method (TMM), global matrix method (GMM), stiffness matrix method (SMM) and finally the semi-analytical finite element method (SAFE). The first three methods are based on the relationships which are derived in the first part of this review. Moreover, TMM and GMM should be considered numerically unstable in the case of a relatively large product value of wave frequency and the total thickness of the composite plate. However, SMM seems to be unconditionally stable. The last method is based on the finite element approach and it can be used in order to confirm the results obtained using the analytical method. Finally, exemplary dispersion curves are presented. The dispersion curves are determined for the 8-th layer of the composite material, which is made of carbon fiber and epoxy resin. It is assumed that the wave front travels in an arbitrary direction.

According to damage tolerance philosophy, a composite component with a flaw is allowed to be operated if it is included in a maintenance program that will ensure damage detection before it reduces the residual strength of the structure below an acceptable limit. One of the damage tolerance approaches includes damage extent identification and monitoring of its growth. In view of the progressive behaviour of damage in composite structures, they should be periodically inspected to monitor damage progression. This article presents an approach to damage size monitoring of composite aircraft structures by means of ultrasonic testing with the C-scan mode and a developed algorithm based on image processing techniques. To test the algorithm, pairs of results of ultrasonic testing of composite elements of aircraft, carried out at time intervals, were used. The analysis of such results is difficult due to the complexity of the obtained C-scans, which is caused by the variable thickness of the aircraft skin and the presence of other elements in the tested structure (e.g. rivets and reinforcements). The proposed method enables the extraction of damage contours, preceded by indication of regions of interest by an expert, and calculation of an increase in the damage surface area, based on two input C-scans, as well as comparison of their contours.

The paper analyses the impact of ceramic particles on the thermal properties and flammability of polymer composites. The research subject concerns polypropylene-based composites. Polypropylene was modified with Aerosil 200 commercial silica and Innosilica silica obtained by means of a modified Stöber method. The input material with a variable content of SiO₂: amounting to 1, 5 and 10% was produced during injection. The heat resistance of the obtained composites was specified by the determining the Vicat softening temperature (VST) and heat deflection temperature (HDT), and based on differential scanning calorimetry (DSC) measurements, thermogravimetric analysis (TG) and thermal diffusivity (Df). A fire resistance test of the studied composites was also carried out. It was found that silica added to the polypropylene matrix has a favourable influence on or does not worsen the heat resistance of the studied composites. It was also noticed that all the composites, especially those with a 1% filler content, have a greater degree of flammability compared to the input polymer.

The aim of the study is a preliminary evaluation of the possibility and purposefulness of applying a gelcoat covering on GFRP (glass fibre reinforced polymer) laminates manufactured by the VARI (vacuum assisted resin infusion) method. A set of panels was manufactured on the basis of three types of glass fibre reinforcements: plain-woven fabric, chopped strand mat and 3D non-crimp fabric, while the composite matrix was epoxy resin. Alternatively, panels with and without the gelcoat layer were manufactured. The polyester gelcoat was laid on the mould by hand. Profilographometric tests were applied as the main method of evaluating the laminate surfaces. To evaluate the border area between the gelcoat layer and the laminate, microscopic visualization was performed with use of a scanning electron microscope (SEM) and - for chosen specimens - with use of a light microscope in Nomarski’s contrast conditions. In order to evaluate the influence of the gelcot layer presence on the laminate mechanical properties, tests of static bending were conducted on the laminates with and without the layer. The obtained profilographometric results showed that application of the gelcoat resulted in improvement of surface quality (a decrease in the maximum and average profile height as well) practically in all the tested specimens. Micrographs made of the gelcoat-laminate border area confirm very good coupling between these two elements. The obtained results of the bending tests showed that the presence of the gelcoat layer does not significantly affect the mechanical performance of the laminates. The registered differences in flexural strength between the specimens with the gelcoat covering and those without it are not big - and in most cases they are in favor of the latter ones. The obtained results allow the authors to conclude that VARI technology is very well suited to manufacturing products with a gelcoat layer. The results and conclusions obtained within the study may be useful for manufacturers in planning and optimization of manufacturing processes for elements made of composite laminates.

The paper presents the results of investigations on Ni-P/PTFE alloy composite coatingsproduced by the electroless method. Ni-P coatings were deposited from two baths differing in composition and pH (acidic and alkaline). PTFE powders with a nanometric size of particles was used as the dispersion phase. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy, roughness measurements and Vickers microhardness measurements. Abrasive wear testing of the Ni-P/PTFE coatings was carried out by friction of the ball at a constant pressure on the sample using a Calotest apparatus. Images of the surface morphology, cross section of the coatings and sample surfaces after wear tests are presented. The coatings are compact and have good adhesion to the steel substrate. Incorporation of the PTFE powder particles in the nickel-phosphorus matrix increases the degree of surface development and hardness of the coating material and increases the wear resistance.

The purpose of the performed study was to provide the best possible representation of the response of a beam subjected to Interlaminar Fracture Toughness testing in Mode II in the course of the End Notched Flexure test. The beam was modelled numerically with the results obtained in experimental tests. Furthermore, analysis was carried out in order to determine the parameters of the traction-separation law in the ABAQUS program defined for the cohesion layer, which have a key impact on the response of the cracking composite beam in the End Notched Flexure test. Experimental tests were conducted on composite beams reinforced with 'E' type fibre glass in an epoxy resin matrix. A composite plate 4.3 mm thick produced in the autoclave process was cut into beams with dimensions of 150 x 25 mm in a manner ensuring an initial delamination length of 30 mm. A numerical model of the composite material with a cohesion layer based on the determined value of fracture energy in Mode II was developed in the ABAQUS program on the basis of experimental tests. The analysis of the impact of the parameters defined in the traction-separation law on the response of the cracking composite beam was conducted on the basis of numerical simulations. The results obtained from the numerical analyses show a strong dependence between the cohesion layer parameters and the response of the composite beam, also in case of a constant value of fracture toughness. It was determined which of the parameters defined in the ABAQUS program have a key impact on the composite cracking process. Finally, very good convergence was achieved for the beam response in the numerical model and in the experiment in terms of force-displacement curves, the critical value of force and displacement causing energy release and crack length in the composite.

The aim of the study was to determine the effect of applying a gelcoat covering on the surface quality and mechanical properties of selected types of glass fibre reinforced polymer (GFRP) laminates produced by the resin transfer moulding (RTM) method. To carry out the investigations, a set of laminate panels was manufactured on the basis of three types of glass fibre reinforcements: plain-woven fabric, chopped strand mat and 3D fabric. They were manufactured by vacuum assisted resin transfer moulding (RTM), alternatively without and with an additional layer of gelcoat. The polyester gelcoat was applied with a brush. As the matrix of the composites, an epoxy resin was used. Evaluation of the manufactured laminate surfaces was conducted using an optical profilographometer, whilst evaluation of the border area between the gelcoat layer and the main structure of the laminate was carried out by microscopic visualization. In order to evaluate the effect of the gelcoat layer presence on the mechanical performance of the laminates, static bending tests were performed. The obtained results allow one to conclude that application of the gelcoat covering resulted in improvement of the investigated laminate surface quality. Decreases in the maximum and average heights of the surface profiles were observed. An especially big difference in the profile height is visible between the 3D laminate without and with the gelcoat covering. Almost all the taken photographs testify to very good coupling between the gelcoat layer and the main laminate structure. The transition between these two elements has a rather discrete character. However, an evident diffusion area occurs in the matrix-gelcoat coupling line and evident penetration of the gelcoat into the fibre strands occurs in the fibre-gelcoat coupling line. It was found that the presence of the gelcoat layer does not have a significant negative effect on the mechanical properties of the laminates. All the tested series of laminates with the gelcoat covering showed a significantly lower standard deviation than the equivalent series of laminates without gelcoat. It means better repeatability of the mechanical properties in the case of the laminates with the gelcoat covering in comparison with those without gelcoat. A consequence of the obtained results is the conclusion that RTM technology is very well suited for manufacturing laminate products with a gelcoat covering.

The article presents a comparison of the physical-chemical and structural properties of TiO₂-SnO₂ nanocomposites obtained by means of two methods: the calcination method and the hydrothermal method. The phase composition of the nanopowders and mean crystallite sizes were determined with the use of XRD analysis. Specific surface area measurements were conducted with the use of the sorption method based on BET isotherm measurements. In order to determine the morphology of the nanopowders, they were subjected to microscopic observations with the use of a transmission electron microscope. The presented methods enable the production of TiO₂-SnO₂ composite nanopowders of a controlled chemical composition varying both in the degree of particle agglomeration and mutual spatial distribution of the composite components, which will undoubtedly find its application in gas detection.

The new generation of prepregs that can be cured without autoclaves, only with the help of vacuum bags and ovens, provide an excellent opportunity for small and medium sized private enterprises to manufacture high quality airframe parts. The design and manufacturing process of an aileron demonstrator made of an MTM46/CF0302 CF/epoxy prepreg, being one of the above mentioned vacuum bag curable ones, is presented. The aileron structure, its fabrication breakdown, the related inexpensive tools made of low thermal resistance polyurethane foam and the curing process allowing for the application of such materials are addressed.

The design of a wing-to-fuselage attachment fitting for composite airframes is a considerable problem since it involves the application of point load to a laminate displaying a relatively low bearing strength. Nowadays the majority of composite airframes are made with the use of CF preimpregnates which make the solution to this problem even more involving. Recently, a new manufacturing technique has been developed that allows for the fabrication of a non-adhesive metal- composite joint especially designed to be used as wing-to-fuselage attachment fittings in the case of composite airframes made with VBO prepregs. In the body of the paper, first, a concise description of the manufacturing process of such a joint was provided, next, numerical stress analysis of the joint supplemented with experimental results was given. The experimental work concerned strain distribution and damage assessment investigated with the help of DIC and CT, respectively.

This paper is an attempt to describe the influence of the stereological properties of the reinforcement on the final material properties. The research was carried out on Al based composites with a heterogeneous reinforcement of Al₂O₃ and C. Various sizes of the carbon particle component (< 40, 80÷120, 160÷200 and < 200 µm) were applied for material manufacturing. The materials were obtained by high energy ball milling and subsequent hot pressing processes. As a result of the milling stage, a reduction in the compound size was observed. First, the real size of the carbon component, the real amount of carbon on the material surface and other properties were measured by quanti-tative metallography methods. Then, the correlations between the obtained stereological parameters and the tribological properties were checked. The analysis revealed that the average size of a single carbon particle and the distance between adjacent particles are the most important factors for the tribological properties of Al-Al₂O₃+C composite design. The larger the size of particles and the greater the distance between the particles resulted in increasing the friction coefficient value. It is related to the homogeneous distribution of the reinforcing component. However, the most surprising effect was discovered during analysis of the areal fraction of C particles. There were no clear correlations between the amount of C particles and the tribological properties. The conducted research revealed which of the analysed parameters are the most valuable for material design and predicting the final properties. Keywords: stereological parameters, tribological properties, aluminum matrix composite, carbon component, high energy milling

Mg based MMCs are increasingly used in automotive and aerospace applications. In this paper, Mg-SiC composites were obtained by the spark plasma sintering method. Various volume contents of SiC particles (5, 10, 15, 20 and 30 vol.%) were used. The samples have near full density, over 98%, and SEM observations confirmed the near full density of the sintered compacts. However, there was an optimum SiC content above which agglomeration of the SiC particles in the microstructure of the composites occurred. Moreover XRD analyses showed that besides Mg and α-SiC, β-SiO₂ (low-temperature β-quartz) and Mg₂Si phases are also present. The mechanical tests results demonstrate that the hardness and compressive strength of the obtained composites tend to increase with an increasing SiC volume content at the expense of compressive strain. The best results of hardness (111 HV_0.5) and compressive strength (346 MPa) were obtained by the Mg-30%SiC composite.

The paper presents the results of tribological studies of nanocomposite nickel/graphene (Ni/G) coatings and, for comparative purposes, of nanocrystalline nickel coatings produced by the electrochemical method on a carbon steel S235JR substrate. To prepare the composite coatings, graphene in the form of flakes was used. The characteristics of the graphene flakes were determined by means of Raman spectroscopy and scanning as well as transmission electron microscopes. The results of studies on the structure and morphology of nickel and Ni/G coatings produced in a bath containing different amounts of graphene are presented. The microhardness of the produced coatings was examined by Vickers measurements. The tribological testing was carried out using Amsler type machines. The wear depth of the coatings as a function of time for the tested Ni and Ni/G coatings were determined. Nanocrystalline Ni/G coatings produced by the electrochemical method exhibit a greater degree of surface development, increased hardness and better wear resistance when compared with nickel nanocrystalline coatings.

This paper presents the results of tests on PLA-based composite materials produced by mixing a base polymer (PLA - polylactide) with PLA fiber. The main aim was to obtain composites with improved mechanical properties. The tested materials contained various amounts of filler in the form of continuous fibers and nonwovens. The samples for the tests were manufactured using the extrusion method. Assessment of their structure and mechanical properties was performed and the results indicate a two-phase internal structure and the filler impact on the increased strength parameters of the obtained composite materials. This offers a possible solution to improve the biofunctional properties of such materials in medical applications.

In this study, the results of fatigue tests using fuzzy set methodology are considered. Cyclic loading causes damage, reducing the strength until the material can no longer sustain even service loading. The experiments demonstrate the scatter of results. Fuzzy set analysis has been proposed in order to estimate the uncertainty in the evaluation of stiffness and critical number of cycles corresponding to final fatigue damage. The results of fatigue-life tests using fuzzy set methodology are also considered when the experimental results are given in the form of a histogram. The fuzzy set and vertex method in conjunction with finite element (FE) computations are introduced to evaluate buckling loads.

The article is devoted to assessing the effectiveness of hydrophobic and air entraining admixtures based on organ silicon compounds. Mortars with lightweight clay aggregate were the subjects of this investigation. Hydrophobisation of the mass was performed using a hydrophobic admixture and surface hydrophobisation was produced using a methyl silicone resin solution with a high VOC content, a water-based emulsion of methyl silicone resin in potassium hydroxide (KOH) and low molecular alkyl-alkoxy-silane in organic solvents. In this paper, measurements of the basic mechanical and physical parameters were carried out. Compressive strength, flexural strength, density, open porosity, total porosity, absorptivity, capability to diffuse water vapour, frost resistance, sodium sulphate corrosion resistance and the thermal conductivity coefficient were determined. The mortars show high absorptivity of about 26%. Hydrophobisation is ineffective after the period of 14 days - the longer the contact of the preparation with water, the weaker the effectiveness of impregnation becomes. All the samples used in the research demonstrated good resistance to salt crystallization after 15 cycles. Impregnation by the use of mineral waterproofing grout (L2) does not protect to a sufficient degree mortar with lightweight aggregate against damage caused by frost. However, surface hy-drophobisation had a considerable impact on the frost-resistant properties of the mortars.

The purpose of this research was to determine the relationship between the delamination resistance of fabric reinforced laminates and the areal weight (AW) of reinforcing fabrics and fibre tow orientations. The laminates were reinforced with 2x2 twill fabrics of AW = 161 g/m² and AW = 395 g/m². The tows making up the wefts and warps were oriented at 0°/90° (denoted +) and +45°/45° (denoted x) relative to the delamination propagation direction. The delamination tests were carried out under Mode I and Mode II quasi static and cyclic loading conditions. These tests were complemented with impact tests. For Mode I loading, it was found that GIc was not dependent either on the AW of the fabrics nor on the tow orientations. Similar results were obtained for cyclic loading. Unlike for Mode I, for Mode II loading the highest G_IIc value was found for the laminate reinforced with fabric of AW = 395 g/m² and tow orientation “x” while the lowest one was for laminates reinforced with the same fabric but of a “+” tow orientation. Drop tests indicated that the laminates reinforced with fabrics of the higher AW had better resistance to impact induced damage.

A novel manufacturing method of Ti₂AlC MAX phases with TiC carbides was elaborated. Compacted from elemental powders, the samples were heated and synthesized in a microwave field under atmospheric pressure. Microwave radiation selectively heats the reactant particles, though additional SiC support was required. Graphite can be classified as a good absorber whereas in Al, Ti metallic particle electric eddy currents are induced only on the surface. Microwaves heat material from the inside to the outside and usually concentrate on the interface between materials with a different dielectric loss factor. Therefore, it is possible to induce and conduct the reaction, on the microscale, at metal-ceramic or even metal-metal contact points. Energy was transferred from the magnetron through the waveguide and after a few seconds synthesis began and spread to the entire volume of the cylindrical sample. The initiated SHS synthesis first proceeded with the formation of Al-Ti intermetallic and TiC precipitates whose highly exothermic reactions resulted in a significant increase in temperature to ca. 1600°C. Next, these phases are almost completely transformed into plate-like Ti-Al-C MAX phases forming a porous structure of the samples. Such materials can be ideal for components working in extreme conditions (heat exchangers, catalyst substrates, filters) or for composite reinforcing.

The paper concerns the numerical testing of a GFRP composite box beam reflecting, on a 1:2 scale, the central part of the superstructure of the recently designed original GFRP composite 5-box footbridge manufactured using infusion technology. The beam is composed of two laminate shells combined with glue on contact strips. The shells are glass-vinyl ester laminates protected with gelcoat and topcoat layers, respectively. The main constituents of the laminas are bi-directional balanced stitched E-glass woven fabrics and flame retardant vinyl ester resin. After homogenization, the composite forming a lamina (reinforced with one fabric) is modelled as a linearly elastic-brittle orthotropic material. Experimental identification of the material constants was done for the new composite and for the aged composite after 5-year environmental ageing, at three service temperatures, i.e. -20, 20, 55°C. The accelerated 5-year environmental ageing of the composite was performed using an ageing chamber and the relevant ageing programme. The study presents the numerical modelling and simulation of the static three-point bending test of the new and aged box beam, at the three service temperatures. The modelling and simulation, performed in the MSC.Marc system, was validated in a previous paper by the authors, based on the experimental three-point bending test of the new beam at room temperature. Comparative studies were carried out in order to determine the effects of the service temperatures and the 5-year environmental ageing on the load capacity of the GFRP composite box beam. Keywords: glass-vinylester composite, mechanical properties, GFRP composite box beam, three-point bending test, modelling and simulation, temperature and ageing effects

Microstructural graded hollow cylinders were processed and characterized using the developed method called centrifugal slip casting (CSC). Water based slurries containing alumina and nickel powders were tested in this work. Two series were produced by the CSC technique at mould rotational speeds of 1000 rpm. The samples were prepared with a solid content of 50 vol.% with 10 and 20 vol.% nickel particles with respect to the total solid volume, respectively. The microstructure along the radial direction of a cross-sectional sample was presented. No new phases were observed after sintering. Microstructural observation and EDS analysis showed two zones with various concentrations of Ni particles in both series along the radial direction of the cylinders.

The phenomenon of a lightning strike occurring during aircraft operation may seriously affect the integrity of its components due to the electrically insulating properties of polymers and polymeric composites used for manufacturing the fuselage elements of an aircraft. Due to the very high magnitude of temperature fields appearing during lightning strikes, decomposition and vaporization of the matrix and reinforcement materials occur. This results in a pyrolysis reaction and leads to rapid degradation of polymeric composites. One of the ways to limit such degradation is to make the matrix electrically conducting. Such a material is currently being developed by the authors’ team. In order to perform preliminary evaluation of the ability of the new material to minimize temperature magnitude and degradation during a lightning strike, a comparative study with a carbon fiber-reinforced polymeric composite, typical for aircraft applications, was performed. The comparative analysis was performed based on the coupled thermal-electrical analytical model of the considered composites subjected to a lightning strike. The obtained results show that the developed material, due to its electrical conductivity, receives much less thermal energy during a lightning strike and thus, minimizes degradation processes. Keywords: aircraft structures, lightning strike, conducting polymers, electrical conductivity, heat-induced structural degradation

The paper presents the basic knowledge for designing cylinder sleeves made of hybrid composites containing solid lubricants. The matrix for the described composites could be aluminium wrought alloys used for manufacturing pistons, for example AlCu4Ni2Mg or cast aluminium-silicon alloys used for blocks and cylinder sleeves for engines and compressors, for example AlSi12NiCuMg. These composites should contain two kinds of reinforcing phase, i.e. strengthening Al₂O₃ or SiC foam and thin layers of glassy carbon. Ceramic foam increases the compressive strength and wear resistance of the composite and decreases the thermal conductivity. Glassy carbon plays the role of a solid lubricant. A cylinder sleeve manufactured of a composite containing particles or spheres of aluminium oxide will possess other properties than one made of a composite containing silicon carbide. The reason for that is the different thermal conductivity for Al₂O₃ (
λ= 20÷30 W/(mK)) and SiC (λ
=100÷130 W/(mK)). Cylinder sleeves manufactured of a composite containing ceramic foams (Al₂O₃ or SiC) will possess a similar, but much lower thermal conductivity (for Al₂O₃ foam
λ = 0.2 W/(mK) and SiC foam
λ = 0.12 W/(mK) at temperatures of 20÷200°C. It is very important for air compressors in which the piston rings are manufactured of composite plastics.

In this study, the elastic wave propagation phenomenon was used to detect the initiation of fatigue damage in a composite plate with a circular hole. The Structural Health Monitoring (SHM) system based on the active pitch-catch measurement technique was proposed. Two configurations of measuring points location were taken into account. The signals from the intact structure were compared with the dynamic response from a structure having a relatively small, interlaminar defect. The influence of the measuring points (actuators and sensors) location on the effectiveness of the damage detection method was performed to obtain an efficient system which can detect the initiation of fatigue damage in a composite plate with a circular hole.

Microspheres are formed during the mineral transformation stage in coal combustion. Their content in fly ashes from the combustion of different types of coals varies over a rather wide range from 0.01 to 4.8 wt.%. The microspheres have three main elements, silicon, aluminum and iron, the oxides of which account for about 89.0 wt.% of the material. Mineralogical analysis using XRD shows that microspheres mainly contain mullite and quartz as the main crystalline phases. The size of microspheres varies between 5 and 500 µm and the most common dimension is 20÷300 µm. Microspheres are characterized by a low bulk density (0.2÷0.8 g/cm³) and can be easily separated by gravitational methods in the form of a concentrate in aqueous media or collected from the water surface of lagoons intended for storing of fly ash and slag. The unique properties of microspheres suggest the wide range of their use. They are currently used as lightweight filler which improves the thermal insulation properties of mortars and concretes based on mineral binders.

The effect of a 5 vol.% chromium diboride addition on the microstructure and properties of sintered titanium diboride was investigated. The preliminary results of studies of TiB₂-5CrB₂ composites sintered by SPS were discussed. The density, Young's modulus and Vickers hardness of the obtained sinters were examined. Microstructural examinations were carried out by SEM. It was found that sintering TiB₂ ceramics by SPS at temperatures of 2000 and 2200°C for 10 minutes is not sufficient. The results of testing the physical and mechanical properties of TiB₂-5CrB₂ composites have shown that the use of CrB₂ may be a good way to obtain a composite material for high performance applications. The best properties were obtained by the composite materials sintered at 2200°C. The results will serve as a basis for further optimization of the SPS process for composite fabrication.

This paper presents the results of research on the properties of composite coatings with a nickel matrix and diamond nanopowders as the dispersed phase. The coating deposition processes were carried out in a Watts bath containing organic compounds and dispersion particles in the form of nanodiamond powder. The characteristics of the dispersed diamond phase were determined using a transmission electron microscope and X-ray diffraction identifications. For comparison purposes, the research also covered pure nickel coatings with nanocrystalline structures. The morphology, topography and chemical composition of the produced coatings were analysed using a scanning electron microscope equipped with an EDS detector. The microhardness of the nickel and composite coatings were measured using a Vickers microhardness tester. The tribological properties of the manufactured coatings were studied using a Calotest. The structures of the produced coatings were found to be compact. Compared to the nickel coatings, the Ni/diamond composite coatings were found to have greater microhardness and stronger abrasive wear resistance.

The aim of this study is to investigate the mechanical properties of polymeric composites prepared by means of extrusion and injection moulding. Three stable thermoplastic polymers (high density polyethylene, polysulphone and polyamide) were used as composite matrices. Antibacterial silver nanoparticles nAg were used as the modifying phase. The mechanical properties of the tested materials were determined during uniaxial stretching. Such parameters as Young’s modulus E, tensile strength Rm and elongation at maximum force εFmax were measured. The results show that neither the preparation technology nor the amount of modifier impair the mechanical properties of the tested composites. The addition of silver nanoparticles does not cause a loss of strength, while it increases the Young’s modulus of the materials.

In the present paper the spherical silica material Innosilica was proposed to be used as filler for a composite with polypropylene. The spherical silica synthesis was based on a modified Stöber method. The aim of the study was to obtain a composite of better properties than those of pure polypropylene. The composite system with 1, 5, 10% of silica fillers were used. The characteristics of the obtained systems were defined by scanning microscopy. A universal fatigue testing machine Zwick Roell Z020 was employed to determine the tensile properties of the input material and composites under static extension and to the test of flexure resistance of the composites. The impact test with a composite notch and input material was determined using an Instron pendulum hammer type and the hardness property was measured with Shore hardness tester with a sharp conic indenter made by Zwick. As the reference material unmodified polypropylene and it’s composite with market silica - Aerosil 200 were used. The results of our researches indicate that the presence of the silica fillers improved the polypropylene properties. Parameters change depending on the content of the fillers. Innosilica allowed to obtain better results than the commercial silica. The study showed that the mechanical properties of silica-filled polypropylene material depend on weight ratio of the individual components of their constituent and on the geometry also. The filler of a spherical construction has a greater influence on the increase in composite stiffness than a filler of an irregular shape (Aerosil 200). This suggests that the higher structural homogeneity of composites PP/Innosilica exhibits the better mechanical properties.

The presented work is devoted to the problem of the optimal design of a multilayered composite structure. A square composite plate of geometrical dimensions 250x250x3 mm with a circular hole of diameter d = 100 mm is investigated. The structure is made of composite material, which consists of N = 12, 16 or 20 layers. Each layer is made of the same material, namely carbon fibers with epoxy resin (CFRP, fibers T300, matrix N5208). It is also assumed that the feasible fiber orientation angles are 0º, ±45º, 90º. The layer stacking sequence is symmetric with respect to the middle surface of the studied plate. The structure is subjected to uniform tension in the horizontal and vertical directions. Calculations are performed for the following load ratios, namely: p_hp_v = 0, 0.5, 0.75, 1.0, where p_h and p_v denote the load in the horizontal and vertical directions, respectively. The optimization problem is stated as follows: we look for the stacking sequence (the number of layers with fiber orientation angle equal to 0º, ±45º, 90º, respectively), which ensures the maximal value of the load multiplier. In order to find the solution to the optimization problem, the advanced concept of the discrete design variable is introduced. The use of these variables significantly simplifies the optimization process. In consequence, a very simple optimization procedure can be utilized. All the necessary computations are carried out with the use of the commercial finite element package ANSYS 12.1. The analyzed plate is modeled as a shell structure. The optimal solution mainly depends on p_hp_v. The total number of layers also has a slight influence on the obtained solution. The results are presented in graphs and collected in tables.

The study presents the results of investigations of the influence of niobium oxides and the addition of carbon on the pressureless sintering of niobium carbide powder and the properties of the obtained sinters. For this purpose, niobium carbide of a specific deviation from stoichiometry was synthesized (NbC_0.8). After the crushing process, all the characteristics of the powder were determined and the powder was found to contain niobium oxides in the quantity of a few percentage of the weight. Next, samples were prepared without any additives and with additives of 1 and 2% of carbon weight. The samples were pressureless sintered at the following temperatures: 1900, 2000 and 2100°C in argon flow by heating them at the final temperature for 1 hour, then their apparent density was measured. A qualitative and quantitative analysis of the microstructure was performed on metallographic micro-sections and the phase composition of the sinters was determined. It was found that the presence of niobium oxides in the NbC powders has an advantageous influence on the sintering process. Single-phase polycrystals can be prepared by the addition of carbon. Some mechanical properties were additionally determined from the sinters including: hardness and fracture toughness and next, an attempt was made to correlate them with the image of the microstructure of the composites and single-phase polycrystals.

The application of NiTi shape memory alloys as long-term implants is dependent on ensuring better biocompatibility of the alloy, which is achieved by modification of the surface by protective coatings or layers. In the present work, the surface of the NiTi alloy was covered by biocompatible composite coatings. First, a thin rutile layer was formed by autoclaving. Passivation was carried out at 134°C for 30min which resulted in forming an amorphous TiO₂ thin film. Next, a biphasic calcium phosphate (BCP) layer was deposited using electrophoresis (EPD). The BCP layer was composed of hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). The deposition voltage ranged from 40 to 80 V at a constant time of 60 s. The deposited samples were vacuum-sintered at 800°C for 2 h. Observations of the surface revealed that the obtained coatings are crack-free. Measurements done with X-ray diffraction confirmed that the top layer consisted of β-TCP and HAP.

The aim of the study is a comparative evaluation of panels made of GFRP laminate (10 layers of plain-woven 0/90 glass fabric) by RTM and VARI methods. The evaluation was performed on the basis of the analysis of the laminate thickness, fibre volume fraction and flexural strength. An essential element of the evaluation is the repeatability of the analyzed properties, which is estimated by the standard deviation and coefficient of variation of respectively numerous result series. Comparison of the two mentioned technologies may be significant information concerning their alternative applicability. The range of the study covers: preparation of four reinforcement lay-ups (preforms) of plain-woven glass fabric, manufacturing four laminate panels using the preforms - two by RTM and two by VARI, cutting specimens from the panels, evaluation of the thickness and fibre volume fraction of the specimens, and evaluation of the flexural strength of the specimens in 3-point bending tests. Laminates manufactured by the RTM and VARI methods showed a relatively high reinforcing fibre volume fraction. A slightly higher volume fraction and, at the same time, a significantly smaller thickness were observed in the VARI laminates. The laminates manufactured by RTM showed about a 10% higher flexural strength in comparison with the VARI ones. The laminates manufactured by VARI showed a higher volume fraction but it is probably due to gas voids present in areas near the reinforcing fibre strands. The presence of voids was also proved in the structure of the RTM laminates, but they are of a different nature - they are bigger and are located within the resin-rich areas between the reinforcing layers. The quality of the specimen surface (two-side smoothness in the case of the RTM laminates, one-side smoothness in the case of the VARI ones) could also have some effect on the flexural strength. In the case of both the VARI and the RTM laminates as well, a visible thickness "gradient", directed the from outlet to inlet, was observed. It is caused by "relaxation" of the underpressure after passing of the resin flow front during the impregnation process. The "gradient" is bigger and less uniform in the case of the VARI laminates than in case of the RTM ones. The RTM method occurred to be minimally better than the VARI in terms of repeatability of the fibre volume fraction and flexural strength, measured as the variance coefficient of the results of a specimen series. The worse repeatability of the laminates manufactured by the VARI method results from the bigger laminate thickness "gradient".

The application of structural non-oxide ceramics is at present a common trend in machines and the construction of mechanical devices. Dense ceramic sinters made of silicon carbide or silicon nitride very often replace metallic parts. The advantages of ceramics are especially evident when they work as parts of machinery exposed to the action of loose and hard particles. The paper compares the abrasive wear susceptibility of both the mentioned phases and two particulate composites made on SiC and Si₃N₄ matrices. Two types of tests were performed. The Dry Sand Test, which indicates the wear susceptibility of the material to wear during the abrasive action of hard particles without any lubricant, was the first one. The Miller Test was the second. This test examined the wear of materials during the action of hard particles in a wet environment (pulp). In both tests the same abrasive, silicon carbide powder, was used.

The recent years of intensive development in construction as well as growing demands has resulted in much greater attention paid to concretes for special applications, such as lightweight structural concretes. The advantage of lightweight structural concretes lies in the lower weight of the construction elements (the density of lightweight concretes equals less than 2000 kg/m³) and high strength parameters, which further lead to lower production costs. Moreover, lightweight concretes can be considered so-called ”green products”, as lightweight aggregates received from waste materials, such as fly ashes, are used for their production. Conducted research has shown that aloxite usage has a great influence on the physical and mechanical properties of lightweight structural concretes. The best results were achieved for a concrete mix with an additive of finegrained aloxite particles. The presence of aloxite fine fractions (F280) in concrete contributed to condensation of the cement paste structure and strengthening the interfacial transition zone between the porous lightweight aggregate and cement paste, improving the physical and mechanical properties of the concrete composite. It was shown that the compressive strength of concrete samples with an aloxite additive increases by about 25÷35% in relation to reference samples. Moreover, the aloxite additive improved the resistance to abrasion by about 30÷40% in comparison to concrete made without additives. In addition, the research proved that aloxite particles show a plasticizing effect and facilitate stirring of the concrete mix, especially in the presence of lightweight aggregate, which leads to a more homogeneous structure of concrete and improvement of concrete tightness by about 35÷50% in relation to the reference concrete.

In this paper, we proposed a new synthesis method of a CuO-SnO₂ composite based on the sol-gel technique and tin(IV) acetate as the precursor. In addition, for the first time we used a combination of high-energy homogenization and spray drying. The aim of the study was to obtain a nano-composite with a high Cu content. The system properties were investigated using XRD, TGA, TEM and SEM-EDS techniques. The obtained composite material contains an amorphous gel of tin(IV) hydroxide and crystalline copper(II) acetate. The presented method of synthesis allows for obtaining nano-composite particle sizes less than 50 nm, and a CuO-SnO₂ nano-composite fraction with a particle size less than 5 nm. The small size of particles should result in high activity of the system.

The aim of the work was to assess the effectiveness of a simplified simulation procedure of the VARI (vacuum assisted resin infusion) process with the use of PAM-RTM® software on mat, plain-woven fabric and unidirectional fabric preforms. The performed experimental determination of permeability, followed by its application in the simulation, exhibits an error of a few to a dozen % of the resin front range - process time relation. At the same time, it was stated that the samples with high anisotropy exhibit a larger simulation error. The cause of the simulation errors is the stochastic course of the actual VARI process, disturbed by such factors as: structural anomalies in the fabric, incomplete hermeticity of the vacuum system, nonuniformity of the resin accumulation behind the front and a non-uniform flow of the resin at the initial stage of the process. The simulation error was also affected by: insufficient mesh density, tetrahedral shape of the finite elements as well as a simulation function different than the actual one. The simulation errors observed for the simplified method are not large, considering the stochastic type of the process, and they make it possible to practically apply the simplified simulation method. The latter can be especially attractive for small and medium enterprises, as its only requirement is to perform simple VARI experiments on small samples and to possess the appropriate software and a standard PC (personal computer).

The results of examinations of polyamide 6 with quartz sand and glass fiber composites are presented. A composite was made using an extrusion machine collaborating with a granulator. The samples for the examinations were made using a Krauss Maffei KM65-160C1 screw injection moulding machine. Samples from polyamide 6 were also made to compare the properties of the composites and unfilled polymer. Investigations of the mechanical properties: tensile strength and hardness were carried out, and also the structure was determined by means of scanning electron microscopy. The aim of the investigations is to determine the influence of the filler on the composite properties and to receive a new, cheaper constructional material. The properties of the composite were determined from samples produced by injection moulding. As a result of such a method of sample preparation, the properties were conditioned by the processing parameters. The investigations were performed in order to estimate the processing capability and usability of PA6 composites with quartz sand and glass fiber addition. The lowest value of tensile strength of the polyamide 6/quartz sand composite was obtained. An increase in the hardness value of PA6 filled with quartz sand and glass fiber was obtained. The character of the changes of tensile strength and hardness values for the examined materials was evaluated, which proves the essential influence of the filler addition on the mechanical properties change. The tensile strength of the composite increases, while the hardness increases as the content of quartz sand and glass fiber increases.

Polyaniline (PANI) is a conductive polymer material with a huge potential for constructing different electrochemical devices. Different strategies can be used to modify and optimize polymer properties from the point of certain applications, e.g. for the construction of gas sensors. Among those strategies, the formation of composite materials comprising PANI as the base material and ceramic powder material as a modifier is a promising approach. In this work the results concerning the influence of CaTi_0.8Fe_0.2O₃ (CTFO) powders on some physicochemical properties of polyaniline (PANI) were presented and discussed. The materials were obtained by the polymerization of an aniline solution where CTFO powder, prepared by the solgel method was added. The microstructures of the materials were characterized using Scanning Electron Microscopy (SEM), the structure and phase composition was tested by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The electrical properties of the developed PANI-CTFO composites were determined using Electrochemical Impedance Spectroscopy (EIS). The gas sensing properties of the constructed sensor devices in the presence of water vapor were tested by measurements of DC electrical conductivity changes as a function of water vapor partial pressure. The current-voltage (I-U) characteristics were also used to characterize the influence of CTFO material on PANI electrical properties. It was found that the introduction of CTFO into the PANI host material leads to substantial changes in the material properties comparing to unmodified PANI. The discussion concerning the influence of the used modifiers on the structure, microstructure and electrical and sensing properties of the developed materials and observed correlation is also presented. The mechanism of the observed influence of CTFO on PANI properties is also proposed. The dominating role of the PANI-CTFO interface on the material properties is postulated.

The present study is an attempt to evaluate the developed exclusive technology for the production of high quality thinwalled Z profiles from Fibre Metal Laminates on the basis of an aluminium and epoxy-glass pre-impregnate using the autoclave process. The research examined Fibre Metal Laminates (Al/GFRP) based on metal sheets made of aluminium alloy and pre-impregnated tape made of glass fibres in an epoxy resin matrix. FML were produced in a 3/2 lay-up (three aluminium layers and two composite layers in 0/90 configuration). The following conclusions have been drawn on the basis of our exclusive technology for the production of thin-walled profiles made of FML laminates: (1) the hardening technology for preformed components in the autoclave process ensures the achievement of excellent dimensional tolerance of thin-walled profiles made of FML; (2) no delaminations, cracks, gas blisters etc. were detected by means of structural tests; (3) the process of forming Fibre Metal Laminates by means of component pre-forming does not significantly limit the values of selected profile angles. In the case of proper precision of component pre-formingand maintained regime in the case of the FML laminating process, the risk of structural defects, including profile corner zones, is significantly limited.

The research proved that polyester fibres, when added to concrete (2% of volume), improved its fracture resistance, however, the effectiveness of the fibres depended greatly on the strength class of the concrete. Much better co-operation of the fibres with the cement matrix was observed in the case of C25/30 class concrete. The application of higher class concretes (C35/45) results in decreased ability of the fibre to transfer loads after the cement matrix cracks. The addition of fibres seems to be positive in terms of the compressive strength. Depending on the concrete formula, for composites with polyester fibres a 6 to 15% increase in compressive strength was observed, as well as a decrease in abrasibility by 20÷50%.

Shear thickening fluids (STF), which are included in non-Newtonian fluids, are a good example of innovative ceramic- -polymer composites. Their characteristic feature is that the viscosity increases with an increase in shear rate. The energy is dissipated during the impact due to the increasing resistance of STF. This is the reason why STF are so promising for applications protecting the human body. Body armours based on STF, because of their elasticity in comparison to conventional counterparts, proved to be more comfortable. This work is devoted to the development of a new composition of STF with the highest dilatant effect. Based on our research on STF, it was shown that the higher the dilatant effect is, the more energy is absorbed during the impact. In this case, four different systems were prepared in which the main component of the solid phase was submicron silica powders KE-P10 (particle size 100÷200 nm) or KE-P50 (particle size 500÷600 nm). In all the prepared systems, the carrier fluid was poly(propylene glycol) with a molecular weight of 2000 g/mol (PPG 2000). The rheological properties of the systems were determined. The influence of the solid phase concentration, size of the particles and the temperature on the dilatant effect properties were examined. Rheological stability in time was also presented in this paper for certain compositions. The most satisfying results were achieved by the systems with KE-P10 in the amount of 60 volume percent. The dilatant effect at the temperature of 25°C reached 11 243 Pa·s, while the beginning of shear thickening was observed at the shear rate of 0.88 s⁻¹. What is worth mentioning is that the obtained results are repeatable in different time intervals, meaning that the investigated fluid is rheologically stable in time. Despite the drop in the dilatant effect by 70% at higher temperatures, the dilatant effect remained on a high level of 3000 Pa·s. Regarding the obtained results, we can assume that body armour based on the ceramic-polymer composite would be suitable for protection even at higher temperatures.

Fibre-metal laminates are modern composite materials that are replacing certain metal elements in aircraft structures. Such hybrid materials have synergic properties determined by their component properties and configuration. This article presents studies of GLARE laminates consisting of aluminium and glass-epoxy composite sheets manufactured using the autoclave method. 2024T3 aluminium alloy sheets were subjected to chromic acid anodising (CAA) and sulphuric acid anodising (SAA). Three different lay-up configurations of the composite layers were used in the structure of 2/1 laminates: [0°], [0/90°] and [±45°]. Tensile strength studies were conducted using a strength testing machine (MTS 322) in accordance with the ASTM standard for composite materials. Microstructural and fractographic observations were conducted using an optical microscope and a scanning electron microscope (Zeiss Ultra Plus, NovaNanoSEM 450). The tensile strength test did not result in cracking of the metal plies; it was the composite that underwent degradation. After the test, the samples were found to have undergone deformation and delamination as a result of the tension; the laminates with an SAA layer were more greatly affected. The plastic range properties are determined by the fibre configuration. The metal/composite adhesion force was higher than the cohesive force in the composite for all the configurations. The degradation mechanism of the laminate structure during uniaxial tensile strength tests does not depend on the type of anodised layer. The configuration of the fibrous composite layers affects the propagation of cracks in the composite area. Transverse cracking of the fibres, cracking of the anodised layer and decohesion of the matrix with tearing-out of fibres were observed in all the cases. The surface morphology of the fracture caused by the decohesion of the composite in an FML is of the same nature as the fracture in the composite material.

One of the problems concerning carbon nanotube (CNT)/thermoplastic polyester composites, prepared by in situ synthesis, is usually a lower molecular weight of the polymer matrix when compared to a homopolymer polymerized in the same conditions. It results in lower elongation at break/mechanical strength of the polymer, which may diminish the reinforcing effect coming from polymer/CNT interactions in the composite. Extension of the reaction time brings, in turn, problems with extruding the melted composite from the reactor due to its high viscosity and in consequence material waste. The objective of this study was to evaluate the efficiency of the solid-state polycondensation process (SSP), which is commonly applied to thermoplastic polyesters on an industrial scale, as regards poly(ethylene terephthalate) (PET) filled with single-walled (SWCNT) or multi-walled (MWCNT) carbon nanotubes. The experiments were carried out using a laboratory-made vacuum SSP set-up. The presented results prove the relatively high efficiency of the process, however, the material geometry seems to be a key factor. The best results were achieved for samples with the smallest thickness. Moreover the presence of nanoparticles in the polymer does not prevent or hinder further polymerization in the solid, and the reaction effectiveness is even higher in CNT composites when compared to an unfilled polymer.

Dispersing fine ceramic particles in polymer matrices has proved to be one of the most effective ways of enhancing key structural and electrochemical parameters of polymer electrolytes for rechargeable lithium batteries. It is now widely recognized that the phase composition, morphology and surface chemistry of the filler all exert a clear impact on the way it interacts with the polymer host, thus contributing to the final outcome in terms of ionic mobility, thermal, mechanical, chemical and electrochemical stability in lithium cells. In the present contribution we manufactured microporous polymer membranes based on copolymer poly(vinylidene fluoride-hexafluoropropylene) (PVdF/HFP) using a two-step approach originally proposed by Bellcore. A mesoporous silica filler MCM-41 was synthesized and functionalized with chlorosilane. After the effect of functionalization was verified by means of FTIR spectroscopy, the fillers were incorporated in the polymer matrices and the resulting dry composite membranes showed a well-developed porous structure and a high ability to absorb liquid media with the formation of stable gels. The good physical properties of the membranes were attributed to the enhanced compatibility of the filler with the fluoropolymer matrix. The composite gel electrolytes were prepared by soaking the dry membranes with a conventional lithium cation conducting liquid electrolyte and their electrochemical characteristics were determined in terms of the temperature dependence of ionic conductivity and electrochemical window. During the experimental studies we observed high conductivities at room temperatures exceeding about 2*10^‒3 S/cm and decidedly better anodic stability for composite gel electrolytes with an addition of mesoporous silica with and without surface modification.

The dynamic behaviour of thermoplastic samples reinforced with aramid or polyester based nonwoven fabrics has been investigated. Changes in the structural state of specimens through open hole and impact damage could be proved by changes in modal parameters. Furthermore a directionality study has been performed showing clear dependence of modal parameters and fibre orientation. An appropriate frequency band was selected for a robust structural state detection of the samples. Additionally, a special modal hammer device was used to increase the accuracy of determining the modal parameters. This work continues investigations which can serve as a foundation for modal analysis based structural health monitoring (SHM) and quality control systems for composite structures. Keywords: aramid nonwovens, polyester nonwovens, anisotropy, impact damage, open-hole, modal analysis, technical diagnostics, SHM, quality control system

The paper presents the results of studies of nickel-phosphorus/graphene (Ni-P/G) composite layers and, for comparative purposes, Ni-P layers produced by the electroless deposition method. The layers were prepared in multi-component solutions. The used graphene was in the form of flakes of different sizes. The characteristics of the grapheme were determined by means of Raman spectroscopy and scanning electron microscopy. The diffraction analysis of the material, morphology and surface topography of the Ni-P and Ni-P/G layers are presented. The micro-hardness of the material of the produced layers was examined by Vickers measurements. The conducted studies have shown that the Ni-P/G layers prepared by the chemical reduction process are characterized by a higher degree of surface roughness and three times higher hardness in comparison with the Ni-P composite layers.

Vacuum bag only (VBO) prepregs allow for manufacturing composite airframe parts without the need for expensive autoclaves since such prepregs can be cured in ovens with the help of vacuum bags. However, the vacuum pressure must be kept at an acceptable level to obtain low porosity products. One of such prepregs is Cytec MTM46/HTS(12K)-150-35% RW carbon/epoxy VBO prepreg designed for airframe applications. The aim of the presented research was to determine an acceptable level of vacuum pressure in vacuum bags, in particular, and the effect it exerts on the porosity of laminates made with the aforementioned prepreg. For this purpose, UD laminate plates were manufactured under 10, 40, 60, 80 kPa and 96kPa vacuum pressure. Next, ultrasound attenuation displayed by every single plate during ultrasound C-scanning was defined in terms of the so-called full screen height percentage and presented in the form of coloured contour plots. Upon counting the pixels corresponding to each colour, it was possible to determine plate area fractions for each attenuation level. Next, a certain number of specimens was cut out of the plate regions that differed in their attenuation and these specimens were x-rayed with the help of a tomograph, then specialized software was used to determine their porosity. Finally, an experimental relationship between the ultrasound attenuation and specimen porosity was determined.

In this paper, an investigation of the dynamic effects of the low-amplitude, high-frequency excitation of a composite aerofoil by means of integrated actuators on the flow is presented. For this purpose, a well-established elastic NACA 64-418 profile was manufactured from a glass fibre reinforced epoxy resin with integrated active elements. The modal properties of the profile were optimized during the design process in such a way that the spatial distribution of nodes and antinodes of the profile is potentially advantageous for the influence of the flow behaviour around the profile. Additionally, the respective eigenfrequency of the profile should be high enough to efficiently influence the flow. The first numerical and experimental results confirm that the aimed modal properties could be obtained. The optimized profile design has been implemented in the resin transfer moulding manufacturing process and selected low-profile actuating elements were applied after fibre-reinforced plastics consolidation on the inner surface of the NACA profile. The applicability of the proposed flow control approach will be evaluated in detail in a specially developed flow channel in further investigations.

The paper presents the results of research concerning the influence of the method and parameters of mixing polyamide powder (PA2200) and graphene flakes (G) on the formation of a composite powder intended to produce a new composite material - PA-G by Selective Laser Sintering. The mixing process was carried out in a rotary mixer for different mixing durations: 1, 2, 4 and 8 hours. The research results of the influence of mixing time on the structure and homogeneity of the PA-G composite powder are presented. The completed studies have shown that mixing time has an impact on the uniform distribution of the disperse phase (graphene flakes) in the volume of the PA-G composite powder particles. The 8-hour mixing time caused mechanical bonding of the powder particles, in the form of so-called neck, which is typical for selective laser sintering of powders (SLS).

The paper presents preliminary tests of an innovative laminar noise-dampening layered structure for industrial purposes, based on PUR foam containing a foam-recyclate. The test cycle included static tensile tests of foam specimens, acoustic dampening tests, technological gluing tests (foam layer with functional layers: magnetic foil and aluminium foil), foam and glue selection, static shear tests of the bonds between the foam layer and the functional layers. The results of the technological and the acoustic tests showed that application of the foam-based layered packet-structures is a very good method for noise-dampening of work-stands in industry. The demountable bond between the packet and the metalic wall is effective and simple to use. It enables application of the packet differentlyly on various work-stands. The static mechanical properties of the foams and of the glue-bonds were satisfactory and show the trouble-free, self-supporting behavior of the dampening packets.

The presented research was devoted to determining the influence of impactor geometry on the degree and character of failure of a glass fibre reinforced epoxy matrix subjected to low-velocity impact. Furthermore, the relevance of impact energy and lay-up configuration of each composite plate were analysed. The subject of the tests were autoclave manufactured 8-ply glass/epoxy prepregs of the following lay-up [0/90]_2s, [±45]_2s and [0/±45/90]_s. The laminates were subjected to low-velocity impact tests according to norm ASTM D7136 with the application of hemispherical impactors: 12.7 mm (0.5"), 25.4 mm (1") and 38.1 mm (1.5"), for three impact energies 5, 10 and 15 J. The conducted tests indicate the correlation between the diameter of the indenter and the load applied, on the degree and character of damage of the glass/epoxy composites, i.e. the higher the load, the greater the laminate failure, regardless of the lay-up configuration. Similarly, the degree of failure is greater when the diameter of the hemispherical impactor is smaller. The dominating types of failure are delaminations at the interface between the composite layers, and matrix cracks. This might occur as a result of considerable shear stresses at the laminate interface and delamination observed after impact with a smaller-diameter impactor. This is best observed in the case of a quasi-isotropic lay-up configuration, where the superposition of the delamination surface area was the highest. The use of a hemispherical impactor of the largest diameter causes bending stresses in the lower layers of the composite, and the presence of characteristic cracks in the matrix and/or at the fibre/matrix interface.

The paper presents results of an evaluation of the reinforcing phase particles in identical test castings of small overall dimensions, obtained from a composite suspension in diversified casting conditions. The composite suspension behavior has been studied in different casting conditions: gravitational, gravitational aided by subatmospheric pressure and under centrifugal force. The beneficial influence of the factors intensifying the process of filling mold cavities with a composite suspension was found. Gravitational casting of the composite suspension is limited by the size of the casting modules - in the analyzed experiment conditions they cannot be lower than 1.4 mm. In the castings obtained using subatmospheric pressure, uniform distribution of the reinforcing phase particles was found. Additionally, highly diversified particle distribution was observed in castings from a suspension subjected to centrifugal forces.

In this study copper matrix composites with two types of additions i.e. graphene platelets in the amount of 1÷2 wt.% or multiwall carbon nanotubes in the amount of 1÷3 wt.% were studied. Two types of graphene platelets were applied: of a fine thickness of 2÷4 nm and coarser of a 10÷20 nm plate thickness. The addition of finer graphene platelets to copper causes less strengthening, but smaller electrical resistivity, while the addition of MWCNTs causes an increase in hardness in comparison to graphene platelets and slightly higher resistivity growing with the amount of nanotubes. SEM and TEM studies allowed to determine that carbon nanotubes and copper grain size are refined during milling which does not change after consolidation. In the samples with graphene, a more homogeneous distribution of platelets was observed in the case of fine graphene, while platelet conglomerates in the case of coarser graphene tend to occur after the consolidation process at the copper particle boundaries.

This work is devoted to the development of the composition as well as analysis of the rheological properties of shear thickening fluids (STF) based on pure halloysite (mineral from aluminosilicates group; H) and silica (SF14) doped halloysite dispersed in various organic liquids. The objective of this study was to form an intelligent composite using aluminosilicate tubes to dissipate energy and verify the applicability of the final suspensions to produce liquid armor. Halloysite is considered cheaper and more environmental friendly than pure SiO₂ for STF production. Herein, we present studies concerning the effects of the molecular weight of poly(propylene glycol) (PPG) and modified aluminosilicate by mixing in ethanol with a carrier fluid. We also report that the fabrication of STF with silica doped halloysite leads to novel organic/inorganic composite materials with unprecedented protection properties. By analyzing the results obtained from the study, it was concluded that the liquids with modified halloysite as a dopant of 1, 3, 5 and 10 vol.% solid phase had a higher viscosity than the reference liquid based only on nanosilica. The fluid with the most favorable rheological properties is the slurry based on nanosilica with 1 vol.% halloysite (previously mixed with EtOH and PPG 725) dispersed in a poly(propylene glycol) of 725 g/mol molecular weight. The maximum shear thickening value of this liquid equaled 557 Pa∙s at a shear rate of 7.8 ^s‒1. In the final step of the research, a knife penetration resistance test was performed. It was observed that the protective properties of p-aramid fabrics interleaved with STF based on pure SF14 powder and doped with halloysite are comparable. Thus, synthetic nanosilica can be partially replaced.

Since deformations induced in composite elements during curing are a problem well-known to engineers that design composite structures, compensating for them is one of the most interesting issues in the field of composite manufactur-ing. The present work proposes a simple method that allows one to predict process-induced deformations. Development of the method starts with determining and measuring in experiments the factors that contribute to the deformations. These factors are then used in the FEM model to calculate the deformations of a double-curved composite element. The calculated deformations are verified by comparison to the measured deformations of an equivalent sample element. The comparison shows that the model used in the present work enables one to predict 80% of process-induced deformations of a composite double-curved element. Although the accuracy of the prediction is not excellent, the method enables estimation of the deformations and may be used as a base for significant improvement of composite element dimensional accuracy. Taking into account that the computational model used in the method is simple and may be implemented in commonly used FEM software, it appears to be a useful tool for any engineer dealing with composite elements design.

In this paper, the structure investigations of Ni-TiC composite coatings deposited on low carbon steel (S355J0) using plasma powder transferred arc welding (PPTAW) are presented. A blend of nickel alloy powder with 40 vol% TiC was selected as the precursor material for fabricating Ni-TiC composite coatings. The obtained composite layers were characterized by macro and microstructural examination. The distribution of carbide grains in the nickel matrix was characterized by fractal analysis. In addition, the volume fraction of TiC inclusion in the nickel matrix and coating dilution as a function hardfacing parameters were calculated. Metallographic examination revealed that the coatings obtained within the range of a 60÷80 A welding current have discontinuities in the interface layer - substrate and a number of large air bubbles. The composite coatings obtained with a welding current higher than 80 A were correctly formed. The microstructure of the composite coatings contains large and small irregular titanium carbide particles. As a result of the interaction between the nickel alloy matrix and high energy plasma arc with titanium carbide during the surfacing process, small particles are formed. Both the dilution coefficient and volume fraction of TiC increase with an increase in welding current. The last part of the paper includes the results of the fractal dimension measurements of coating cross-sections. For the analyzed structures, the percentage of TiC and linear fractal dimension were determined using the line counting dimension method (LCD), which is a modification of the box counting dimension method (BCD).

Composite materials were produced by reactive infiltration of a porous intermetallic Al9Cr4 preform whose structure was developed during combustion synthesis. Compacts of Al and Cr powders with a stoichiometric ratio of Al/Cr equal to 9/4 were placed and ignited in a microwave reactor. Due to the low enthalpy of the reaction, the samples were preheated. The reaction starts with partial melting of the Al particles producing a homogeneous structure with open porosity. The synthesis proceeded by intermediate phase transformations reaching a maximum temperature of ca. 1000°C. Next, the preforms were pressure infiltrated with molten Cu with interfacial diffusion of the composite elements. The intermetallic compound decomposed releasing Al which saturated the matrix and formed a Cu9Al4(Cr) phase. Simultaneously, the preform transformed into a mixture of globular precipitates of Cr52Al35Cu13 embedded in the Cu47Al41Cr12 phase. The produced composite materials exhibit significant heat and oxidation resistance. The developed protective layer was composed of Al₂O₃ oxides doped with Cr and Cu and growth with parabolic oxidation kinetics.

This paper presents an electroactivity comparison of Pt/SnO₂ nanocomposites with different metal phase precursors in a methanol oxidation reaction. One of them is a water solution of hexachloroplatinic acid and the second is the platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (known as Karstedt’s catalyst). The Pt/SnO₂ system has a broad range of applications in various sectors of industry. It is a very popular heterogeneous and electrochemical catalyst as well , especially in fuel cells. This effect is due to the presence of platinum. As the most expensive component of the catalyst it is still a barrier to its widespread use, hence, the constant search for new, cost-effective methods of obtaining this kind of systems. The aim of the research was to obtain a highly active Pt/SnO₂ catalyst with a low metal concentration in an electrochemical system. The small size of the Pt crystallites should result in high activity of the Pt/SnO₂ system. We proposed two synthesis methods of the platinum catalyst based on the sol-gel technique and tin(IV) acetate as the SnO₂ precursor in conjunction with the use of inorganic and organic sources of the metallic phase. The presented method of SnO₂ synthesis allows for obtaining nano-support and in the next step - a nano-catalyst. The system structures were investigated using TEM and XRD techniques to describe their thermal structural evolution. To study the influence of the metallic phase precursor, we used cyclic voltammetry (in acidic media), which is the best method to check the activity of the electrocatalyst. The results showed high electrocatalytical activity of the nanocomposites, irrespective of the metal phase source. The systems obtained from an organosilicone precursor demonstrate high temperature stability.

The present experimental and numerical research is focused on a box composite beam, so-called a validation segment, consisting of two vinylester/glass shells glued together. The top shell has a hat cross-section, whereas the bottom one is flat. The shells are glued together at two horizontal contact strips. The validation segment reflects the central part of the cross- and longitudinal-section of a box composite superstructure of a footbridge designed by the authors. The dimensions of the cross- section and the number of fabric layers in the validation segment are decreased twice in comparison with the footbridge superstructure. Moreover, the composite beam was rotated by 180° in relation to the footbridge. The validation segment is 2.35 m long, and the cross-section overall dimensions are 0.60 m × 0.26 m (width×height). The laminate components, glue and manufacturing technology of the validation segment are the same as for the composite footbridge. The study develops a methodology for numerical modelling and simulation by the Finite Element Method of box composite girders formed as two composite shells glued together. The methodology is developed in reference to the validation segment which is subjected to the 3-point bending test with shear. Experimental validation of the modelling and simulation was carried out for the basic case of new laminates at 20°C. FE computer code MSC.Marc 2010 was used for the numerical modelling and simulation.

Conventional needle-shaped instrument tips under ultrasonic excitation for root canal treatment made of nickel titanium (NiTi) alloys achieve a high cleaning performance, especially when inducing the cavitation phenomenon. Nevertheless, their tendency to spontaneous material failure is disadvantageous. Monolithic polymers, e.g. polyamide (PA) significantly reduce this risk, however, instrument tips made of this material are characterised by low cleaning performance. Fibre-reinforced polymers (FRP) exhibit the possibility to bear dynamic loads at higher life cycles than conventional metallic materials. The use of endless fibre-reinforced polymers allows the realisation of instrument tips offering good damage tolerance and cost-efficiency as well as a high cleaning performance. This paper focusses on preliminary numerical and experimental investigations necessary to prove the suitability of fibre-reinforced materials for endodontic instrument tips. The numerical investigations conducted using a standard FE-Method contain simulations of the eigenfrequencies. The accompanying experiments were done for optical detection of the cavitation effects induced by conventional and fibre-reinforced instrument tips. The calculations and tests of the novel instruments made of PA6 reinforced with carbon fibres (CF-PA6) demonstrate a significantly higher cleaning efficiency and a clear failure tolerant structural behaviour compared to conventional polymer and nickel titanium instruments. The investigations show a large number of influencing factors on the operation of fibre-reinforced instru-ments under ultrasonic excitation. In this context, further tests have to be done to qualify a potential clinical relevance.

The main purpose of this work is to numerically investigate the shear stress homogeneity in the adhesive layer of a double lap joint specimen subjected to dynamic shear loading using the Split Hopkinson Pressure Bar technique (SHPB). This homogeneity is measured through a coefficient defined by the ratio of the standard deviation over the average shear stress in the adhesive layer. Three types of fiber textures of carbon-epoxy composite adherents were examined: unidirectional laminates, 2.5 D interlock H2 and 3D orthogonal. The influence of many parameters related to the adhesive was studied for the three types of composite adherents. For the same percentage of carbon fibers, it was found that the unidirectional composite substrates give the best homogeneity. Moreover, a thicker, shorter and softer adhesive layer ensures the best shear stress homogeneity for all the three types of substrates. The software used for this study is ABAQUS.

The research on the graphene application for the electrodeposition of nickel composite coatings was conducted. The study assessed the important role of graphene in the increased wear resistance of these coatings. A Watts type nickel plating bath with a low concentration of nickel ions, organic addition agents and graphene as dispersed particles was used for deposition of the composite nickel-graphene coatings. The particle contents in the coatings, surface morphology, roughness and microhardness of the coatings were measured. An Amsler testing machine with a block - ring system was used for tribological tests with Lux oil lubrication. The obtained results suggest that the content of incorporated graphen particles increases with an increasing amount of graphen in the plating bath. The application of organic compounds was advantageous. The nickel-graphene coatings produced during the investigation were distinguished by much better tribological properties than the nickel coating. The tested composite coatings had a relative wear resistance from 3.7 to 6.9 times higher in relation to the relative wear resistance of a nickel coating.

The studies carried out were aimed at developing guidelines for the procedure of employing the Acoustic Emission (AE) method for ensuring the required manufacturing quality and operating safety of composite bridge structures. For the studies, the experience gathered in the studies of thin-walled components made for the aeronautics, automotive and boatbuilding sectors was used. The focus was components with a significant thickness (14÷16 mm) which are, by their nature, less homogeneous and can have more defects when compared to thin-walled composites. The studies carried out for the purpose of this work demonstrate the system for the acceptance tests of composite structures. The demonstrator model in question was developed based on laboratory tests of composite components and of parts of a prototypical structure under load, as described in this work. The recorded acoustic signals were analyzed using software enabling the authors to analyze numerous parameters of the signals and to locate the recorded acoustic emission artifacts. The developed procedures were verified in AE tests in four-point bending of a prototype composite beam with the length of 15.3 m. The nominal operating load and loads significantly exceeding the operating conditions were applied for the tests. The results obtained enabled the authors to study the destruction of composite beams. Based on the signal analyses, the sites of local composite damage were identified and the stage when the global structure damage took place was foreseen. Multiparameter analysis of the recorded acoustic signals made it possible to determine the kinetics of defect growth. The results of the tests carried out for this work helped to develop guidelines for the procedure of acoustic emission testing for composite road bridges at the stage of handing them over for use and in the periodic monitoring period for the used bridge structure.

Fiber reinforced polymer composites (FRP composites) are advanced technical materials nowadays, offering broad applications in bridge engineering science. This work is aimed at analysing FRP composite damage in static tensile tests, by assessing the load-carrying capacities of the tested specimens. For the tests, demonstrative scale composites for constructing structural components of the load-carrying girder of a bridge structure were used. Such materials are considered an alternative for steel and concrete today as they have superior strength parameters. This is shown by their higher maximum load values. In this work, several typical types of FRP composites damage in tensile tests are analysed. The damage in the form of local warp degradation (warp crushing) caused by mechanical impact reduced the load-carrying capacity of the specimens by 45%. The manufacturing defects, consisting in textile creasing while placing in the mould, and the introduction of holes for mechanical fixation of structural components also reduce the load-carrying capacity to about 20%.

The study of the physical and mechanical properties of high performance concrete with polypropylene fiber was presented in the paper. Its basic characteristics and physical strength were defined, i.e.: absorbability, density, open porosity, compressive strength, splitting tensile strength, flexural tensile strength and modulus of elasticity. The use of polypropylene fibers results in different wetting and adhesion properties of high performance concrete. The wetting properties of the concretes were determined by measuring the contact angle of their surfaces using two measuring liquids: water and glycerin. Measurements were carried out three times: at the time of application of drops after 0, 5 and 40 minutes. On this basis, the total surface free energy (SFE) was determined. The SFE polar and dispersion components were defined using the Owens- Wendt method. By analyzing the examination results, it can be noticed that the contact angle values depend on the type of concrete. The results of contact angle measurements proved that all the glycerine contact angles (θ_g) were higher than the water contact angles (θ_w), and they decreased in the course of time. The highest contact angle was shown for concrete without fibers both at the beginning of the tests and after 40 minutes. The smallest contact angle with water was obtained by the concrete with the smallest addition of fibers. The biggest SFE difference was observed for the lowest fiber content of 0.5%. This is due to the physical characteristics of this concrete. The concrete with the 0.5% addition of fibers is characterized by the highest porosity, absorptivity, and the lowest density among the tested concretes. This indicates increased wettability and increased adhesion properties. Based on the SEM study, the microstructure and distribution of cracks and pores in high performance fiber reinforced concretes were shown.

The paper presents the influence of the chemical composition and structure of a glassy carbon precursor on the tribological properties of a metal-ceramic composite, manufactured with the application of this precursor. Two groups of composites containing two different carbon precursors have been manufactured and studied. The first composite contained a glassy carbon precursor embedded from the liquid state in a porous ceramic foam with 90% open porosity. The ceramic foam (Al₂O₃) is the reinforcing phase and the glassy carbon functions as a solid lubricant. A twofold increase in compressive strength was observed when the foam was present. The foam porosity was reduced to 85% after it was coated with carbon. However, it was good enough for proper infiltration with the liquid matrix alloy. In the case of the second composite, it is a spatial skeleton made of glassy carbon (RCV) which functions both as the reinforcement and solid lubricant. The open porosity of the carbon foam (95%) promoted good infiltration with the matrix alloy. There was no report of holes which were not filled with the matrix alloy within the entire volume of the samples subjected to microscopic tests. The wettability of the foam surface with the matrix alloy is sufficient enough to form strong bonds. The composite containing ceramic foam coated with glassy carbon showed better tribological properties than the composite which contained only carbon foam.

The paper presents the results of research concerning lightweight, ecological composites produced on the basis of building lime, cement and metakaolin, which are binders, as well as hemps used as a renewable raw material of agriculture. Tests of the physical and mechanical properties of lime-hemp composites were performed and their basic characteristics were determined, i.e.: absorptivity, bulk density, thermal conductivity, compressive and flexural strength, as well as the dynamic modulus of elasticity. The study was conducted to determine the use of lime-hemp composites to construct walls or to fill the frames of a wooden house. The results show that the lime-hemp composites produced are lightweight and have low thermal conductivity and apparent density. On the other hand, they are characterized by very low strength properties compared to traditional building materials. The dynamic mechanical properties of the shives reinforcing the composites depend on various factors such as shives loading, orientation and the nature of the shives-matrix interface region. The addition of ethylene-vinyl acetate copolymer as a plasticizing and strengthening admixture caused a considerable increase in the strength parameters of the composites.

The paper presents the influence of the spatial structure of a glassy carbon precursor on the structure and properties of sliding composites. Comparative studies carried out and the results obtained have been described for composites containing conventional carbon foam as well as those containing glassy carbon foams, from various types of glassy carbon precursors, functioning as reinforcement and a solid lubricant. The application of two different reinforcing phases based on the different types of precursors used, results in producing composites of varied structures and properties. Such a procedure also requires a pressure change in precursor infiltration. The material used for production of the carbon precursor as well as the process parameters of its pyrolysis allow significant modification of the structure and properties of the manufactured composite.

The paper presents a procedure based on numerical analyzes allowing a quick risk assessment of delamination propagation in composite structures during routine inspections. The principle of the procedure is the comparison of size and location of the defect found during maintenance checks with a set of data obtained from series of numerical analyzes in order to determine the potential for growth of the delamination. The decision then can be made regarding the inspected component - whether it can be still used or should be replaced. The data for comparison contains sets of delamination sizes corresponding to critical embedded delamination diameters derived from linear buckling analysis and nonlinear analysis of postbuckling behavior including delamination propagation. The paper shows an example of such a procedure for a structure made of carbon-epoxy laminate. A series of numerical models was created covering all the possible locations of delaminations throughout the laminate thickness. Linear buckling analysis and nonlinear analysis of postbuckling behavior were conducted using the MSC.MARC finite element commercial code. The analysis of delamination propagation is also included based on the Virtual Crack Closure Technique. The critical delamination diameters were determined for each delamination location and the bases for comparison were created.

The aim of this study is to examine the possibility of fabricating ceramic-metal composites with a gradient concentration of metal particles from the Al₂O₃-Ni system. As the method of composite fabrication, centrifugal slip casting (CSC) was chosen. This method is a technique for powder processing, that combines the effects of slip casting and centrifugal casting. In this work one variant of the centrifugal casting method was used. The horizontal rotation axis was applied. Aqueous based slurries (with 50 vol.% content of solid phase) consisting of alumina and nickel powder (10 vol.%) were tested. The macroscopic as well SEM observations confirmed the gradient concentration of nickel particles in the composites.

For the production of composite materials WC-6Co, the spark plasma sintering method was used. As a result of rapid heating and a short sintering time, materials were obtained with a density close to the theoretical value. The resulting sintered materials were measured for density and hardness. The values of the critical stress intensity factor K_Ic and modulus of elasticity were set. SEM and AFM observations were carried out. On the basis of X-ray diffractometers analyses, the size of WC and Co crystallites were estimated, whose sizes are less than 50 nm. It was shown that the rate of heating to the sintering temperature significantly affects the sintered microstructure and consequently their mechanical properties. All the sinters are characterized by a K_Ic above 11.5 MPa•m^1/2. The hardest of the obtained materials (1842 HV₃0) was sintered at a heating rate of 600°C/min for 5 min.

The ceramic-polymer composites presented in the paper have unusual properties. These materials can operate in a wide range of electromagnetic spectrum and consequently they can be potentially used in imaging techniques, chemical characterization, security systems, quality control and very high data rate communication systems. Microwave applications are widely understood as antennas and radiocommunication devices. Materials used to produce equipment operating at high frequencies, even subterahertz, must be subjected to restrictive verification. The most commonly used materials in radio technology are ferroelectrics. They are characterized by a high value of dielectric permeability. A typical example of ferroelectric material used and widely known is barium strontium titanate (abbr. BST), which is applied in microwave technology. Barium strontium titanate was prepared using solid-state synthesis process. The materials used in the fabrication were ceramic powders: BaCO₃, SrCO3 and TiO₂. Thanks to the combination of an elastic polymer and ceramic powder with ferroelectric properties, it is possible to use such a material in devices operating at a very high frequency. The commercial materials used in the research allow one to produce composites by the tape casting method and obtain antennas. Ferroelectric ceramic-polymer tapes based on doped and undoped ceramic powder with different BST stoichiometrics have been prepared. The tunability of samples prepared of pure and doped Ba_0.65Sr_0.35TiO₃, Ba_0.58Sr_0.42TiO₃ and Ba_0.51Sr_0.49TiO₃ was measured. The relationship between the stoichiometry, or doped and undoped powder has been also found. It was observed that a higher ratio of Ba to Sr caused an increase in tunability values. Moreover, the addition of Ni₂O₃ to ceramic powder positively effected the tunability parameter.

The paper deals with the influence of delamination on mechanical characteristics of a composite cantilever beam. The main goal of the performed Finite Element Analysis (FEA) was to recognize the general nature of damage influence on the composite structure’ properties by extraction of eigenfrequencies and eigenmodes. The two main geometrical parameters, i.e. the size and location of a delaminated zone were taken into account. In addition, a simple analysis of the friction coefficient on the beam dynamics was performed. The numerical simulations were done in the ABAQUS/CAE commercial software environment. The models contained a single local delamination with appropriate contact definition. The defect length changed from 10 to 100% of the overall beam length. The results obtained for two different sequences of plies show the significant effect of delamination on the composite structure mechanical properties. In particular, the location of the delaminated zone had a non-uniform influence on the decrease in subsequent eigenfrequencies, which in some cases could help to avoid resonance. In the paper, analysis of the numerical results concentrated on the first five eigenmodes and on small and moderate-sized defects. The importance of other factors, e.g. friction coefficient or boundary conditions, as well as prospective experimental verification of the numerical results were also considered. In the performed analyses, glass-epoxy material data were used.

The presented paper discusses the minimum weight design of multilayered fiber composite plates with tolerances in individual ply thicknesses. These tolerances are given by the maximum acceptable deviation of every individual ply thickness from its nominal value. The robustness of the design is achieved by diminishing the design state variable (buckling load factor) by the product of arbitrary assumed tolerances and appropriate sensitivities. The proposed approach is illustrated with examples of a simply supported rectangular laminated plate design under uni- and bi-axial compression. The minimum weight identified by the total number of layers is found to assure plate stability. For the discussed analysis, buckling load sensitivity formulas with respect to ply thicknesses are given. Based on these relations, the impact of the discussed variations on the optimal laminate stacking sequence and buckling mode shape is studied in detail. The achieved results emphasize the importance of robust design opposed to merely nominal approaches.

The paper presents the results of tribological tests conducted on an A339/SiC/10p composite reinforced with SiC particles. The test method used in the research was the ball-on-disc method combined with variable abrasion test parameters. Different materials were used for the counter-specimen (steel, Al₂O₃, SiC), variable load (5 and 10N) and sliding speed (0.1 and 0.5 m/s). It was found that the use of a counter-specimen made from a material of higher hardness significantly reduced the friction coefficient and the specific wear rate of the tested A339/SiC/10p composite. On the other hand, in all the friction pairs, an increase in the load while maintaining the same test conditions caused a decrease in the friction coefficient value and an increase in the specific wear rate. Additionally, in the Al₂O₃ counter-specimens, an abnormal decrease in the friction coefficient was observed with an increasing load, but it had no impact on the results of the specific wear rate.

The aim of this paper is to present the adoption of the progressive damage model to describe the degradation of polymer composites under ultra-low-cycle fatigue. The first part of the paper is devoted to the presentation of the approach and discussion of the theoretical aspects of the numerical model. The model contains three states describing the material degradation process: undamaged response, point of damage initiation and damage evolution. The second part is devoted to the implementation of the presented model to describe the fatigue life of the polymer composite under ultra-low cycle fatigue. A polymer composite comprising unidirectional layers was modeled as linear elastic with progressive stiffness degradation. The model was loaded in cyclic tension with a sinusoidal waveform. Numerical modeling has been performed using Abaqus software. The results of the numerical analysis results were compared with the experimental results taken from literature.

The paper presents the study of nanocrystalline Ni/Al2O3 layers produced by the electrocrystallization method on a copper substrate. Two variants of Ni/Al₂O₃ layers with different contents (5 and 10 g/dm³) of Al₂O₃ disperse phase in the nickel plating bath and, for comparison a nickel layer of nanocrystalline structure were tested. The Al₂O₃ powder and composite layers were characterized using the following research techniques: scanning electron microscopy (SEM), X-ray diffraction (XRD), optical microscopy, microhardness measurements, measurements of surface roughness parameter R_a and electrochemical corrosion resistance studied by the potentiodynamic method. The paper presents results of the studies of the Al₂O₃ powder, Ni and Ni/Al₂O₃ structure, and the results of microhardness and corrosion resistance in the environment of 0.5 M NaCl. The produced layers have a nanocrystalline structure, are compact and have uniform thickness. The Al₂O₃ powder particles embedded in the nickel matrix increase the degree of expansion of the surface layer and hardness of the layer material. There is no increase in the corrosion resistance of the Ni/Al₂O₃ composite layers compared with the nickel layer in the same test corrosive environment.

One of the ideas to develop structural health monitoring systems is to use piezoelectric transducers generating elastic waves in a monitored structure. In the paper, we present an approach to develop such a system with the use of PZT ceramic (lead zirconium titanate - PZT) sensors embedded into the structure of a composite. Elastic waves actuated in an acoustic medium by a network of PZT transducers can be scattered on the discontinuities of the monitored structure, thus giving a possibility to detect such damages. For composites they can be debondings or delaminations caused by impacts. In that case, PZT transducers can be either bonded to the surface of an element or embedded in the internal structure of a composite. Both methods have their own advantages and drawbacks. Apart from increased sensor durability and lower energy consumption when actuating elastic waves, there are also other, more important reasons for sensor embedding. First, when considering structure repairs with composite patches, it can be hard to use PZT transducers attached to the surface due to their exposure to external conditions. Embedding may also increase the damage detection capabilities of the approach. For multilayered structures like Fiber Metal Laminates (FML), it may allow one to assess the state of each layer separately and to distinguish between inner layers delaminations and debondings between layers made of different materials. In the paper, we present an approach to detecting impact damages of composite structures which are barely visible on the surface (Barely Visible Impact Damage - BVID). The results of impact tests, signal analysis algorithms and the influence of the composite manufacturing process on chosen transducer properties are presented.

The problems with fabricating magnesium matrix composites with aluminosilicate cenospheres were demonstrated. Two casting methods, typical stir-casting and vacuum casting processes were chosen to obtain AZ91 magnesium matrix composites with hollow cenospheres 63÷125 μm in diameter. In both methods, violent reactions between the components precluded the fabrication of the desired composites with undestroyed cenospheres. The main reaction products were oxides and an Mg₂Si compound. The creation of a Ni-P coating on aluminosilicate cenospheres (by electroless plating method) in connection with the application of the vacuum casting process allowed the authors to obtain composites with cenospheres not filled by the matrix alloy. The proposed solution contributed to the fabrication of composites characterized by about 60 vol.% uniformly distributed cenospheres and a final material density equal to about 1.16 g/cm³.

The purpose of the study was to evaluate the possibility to use the thermography method in damage extent analysis for fibre metal laminates subjected to low–velocity impacts. On the basis of the obtained results, it has been found that the thermovision method may be used as a relatively effective method for damage identification in fibre metal laminates. It is possible to use local temperature change monitoring in FML as a diagnostic method for these elements in real time. On the basis of the studies it has been shown that depending on the impact energy, the local temperature changes. The values of this change depend on the impact energy. Moreover, the damage area in which the thermal change occurs is dependent on the impact energy. The damage areas estimated using thermography are similar to the damage areas measured by other methods known as more effective and certain. The energy absorbed by a laminate during the impact process is correlated with the process and type of laminate damage. It can be assumed that the observed thermal changes are caused by the degradation process of the structure as the results of deformation, matrix and fiber cracking, delamination initiation and propagation, friction and laminate perforation.

The results of structure investigations of an experimental magnesium matrix composite reinforced with Ti6Al4V particles in as-cast conditions and after heat treatment are presented. The commercial AZ91 magnesium alloy was used as the matrix alloy. The experimental composite was reinforced with 30 wt.% Ti6Al4V alloy spherical particles. The investigated material was obtained by the stir-casting method. The microstructure of the fabricated composites was characterized by uniform distribution of the titanium particles within the magnesium matrix. The phase composition of the composite was typical for the used component. New phases were not revealed by XRD techniques. Solution annealing at 693 K for 24 h and 48 h (with water quenching), followed by ageing at 423 K for 16 h was carried out. After ageing discontinuous precipitation process of the γ phase (typical for AZ91 magnesium alloy) was observed. The applied heat treatment processes did not bring about changes in the chemical composition between the used components.

This paper presents the results of examinations of wood-polymer composites based on mixed polypropylene (PP) and sawdust. Composites with a different volumetric content of wood were prepared (25, 50 and 70% filler). Injection molding technology was used to obtain the research samples. The authors also employed X-ray diffraction, an optical microscope and a transmission scanning microscope. Based on the X-ray diffraction analysis, the presence of several polymorphic forms of the polypropylene were found in the composites used in the study. The crystalline fraction of the matrix in the studied composites is composed of an alpha phase which crystallizes in a monoclinic lattice and a b phase which crystallizes in a hexagonal system. Microscopic analysis revealed irregular distribution of the wood particles in the matrix of the tested composites.

The goal of this paper is to analyse damage in Fibre Metal Laminates, containing glass and carbon fibre reinfor-ced composites, subjected to low-velocity impact. The analysis is based on the assessment of force-displacement characteristics in the aspect of energy absorption connected with initiation and damage propaga-tion in the examined laminate. On the basis of experimental research and result analysis, it may be stated that: (1) Fibre Metal Laminates with glass and carbon fibres are characterized by higher impact resistance in compa-rison to classic composite structures. This assumption is proved by higher maximum load levels, as well as by higher aggregate absorbed impact energy. Moreover, the aluminium layers can have a protective function as they absorb a significant amount of dynamic impact energy and lower the scope of damage in the laminate. (2) Fibre Metal Laminates with carbon fibres show greater susceptibility to damage resulting from dynamic impact than laminates with glass fibres. The main factors influencing the impact resistance of the examined materials are the properties of particular components, especially the composite reinforcing fibres. Carbon fibres show a relatively small deformation range until failure and are brittle in comprison to glass ones, which raises their su-sceptibility to damage resulting from dynamic impact. (3) Force-displacement (F-d) analysis, aggregate absor-bed impact energy (Ea) as well as initiation energy (Ei) and damage propagation (Ep) may represent some of the more vital criteria of composite materials assessment in terms of their resistance to low-velocity impact.

In the scope of reduced resource consumption and CO2 emissions, lightweight structures in multi-material-design offer a high potential for use in aviation or automotive applications. Though, to take advantage of the specific structural and functional properties of the different materials of hybrid structures, it is necessary to provide adapted manufacturing and joining technologies. This article presents the development of a new ther-moclinching joining process to produce hybrid structures with continuous fiber reinforced thermoplastic compo-sites and metallic components. Based on the principles of staking and the classical clinching process, thermoc-linching technology ensures element free and form-closed joints by plastic deformation of the reinforced thermoplastic component. To approve the technological concept of the thermoclinching process, prototypic jo-ints with both reinforced and non-reinforced thermoplastics were produced and experimentally tested, revealing up to 50% higher failure loads of the reinforced joints. In order to understand the generated fiber reorientation during the thermoclinching process and its optimization, the produced joints were analyzed using non-destructive and destructive testing methods such as computed tomography scans and micrograph analysis. It was shown that parts of the textile reinforcement were purposefully relocated into the neck and head area of the joint and thus considerably contribute to the load carrying capacity of the joint. Process simulations are performed to predict the plastic deformation and the resulting fiber orientation during the joining process. Even now, it can be stated that without the necessity to apply any additional joining elements, the developed thermoclinching tech-nology projects a high lightweight potential for future composite structures.

Modern aircraft structures contain sheathing elements which are supposed to not only carry loads, e.g static ones, but also at the same time possess resistance to corrosion or dynamic impact. As a consequence, new kinds of hybrid materials, e.g fibre metal laminates, were created. They combine the mechanical and physical proper-ties of various materials. Until now, the most common and widespread structures are GLARE® laminates (alu-minium/glass-epoxy composites), characterised by high fatigue and static properties, as well as by impact resi-stance. The concurrent influence of many negative factors during exploitation causes a gradual decrease in the functional properties of these materials. One of the factors affecting e.g. static strength is low-velocity impact. Low-velocity impact often leads to macroscopically invisible damage of the composite structure, with delamina-tions and ply cracking occurring during impact energy absorption. Fibre metal laminates possess a much better dynamic load-carrying capacity, limiting negative ply cracking in the composite and absorbing some impact energy through elastic-plastic deformation. In order to assess the influence of low-velocity impact on the residu-al strength of composite materials, Compression After Impact (CAI) tests are carried out. Normalised CAI te-sting is used for classic 5 mm thick composite structures. However, as the literature suggests, it is not effective in the case of fibre metal laminates, particularly those with a thickness more then 1.1 mm. The work presents an analysis of the possibility of conducting an effective (ensuring valid assessment of strength reduction) CAI test for 1.5 mm thick FML panels after dynamic impact. An alternative workstation construction was proposed, and simulations and experimental verifications were conducted. It was observed that a solution based on the ASTM standard does not apply to thin FML laminated panels. Deformation of the specimen occurs in areas located far from the impact site. As a consequence, the strength values differ neither for plates with impact-induced damage nor ones without it. The proposed alternative holder construction for compression after impact of thin fibre me-tal laminates plates testing eliminates premature material damage. On the basis of the conducted numerical si-mulations, it was stated that using the ASTM holder for CAI test leads to the occurrence of the first buckling mode in the damage area, with stress concentration in its vicinity. Such a form of deformation may allow one to correctly assess the influence of impact damage on FML composites.

The usage of ceramic materials in applications endangered by intensive cavitation could limit erosion phenome-na. Especially effective improvement could be achieved with the application of sintered ceramic matrix compo-sites (CMC). The presented work describes the cavitation wear resistance of a few CMCs in comparison to mo-no-phase ceramic sinters made of alumina and tetragonal zirconia. Their degradation was described by the volumetric loss of material. Additionally, the cavitation degradation mechanisms of each particular material were determined by detailed observations of worn surfaces at different stages of wear.

In recent years the technology of manufacturing dense composite sinters with submicrometric grains in the alu-mina/yttria-alumina garnet (Al2O3-Y3Al5O12) system has developed. The garnet grains are very uniformly di-stributed in the alumina matrix due to applying special chemical methods. Such a material shows a higher hardness, comparable fracture toughness and almost a one order of magnitude lower wear susceptibility when compared to alumina sinters. The drawback of this material is its relatively low strength. This work presents the results of experiments on improving the mechanical properties of the Al2O3-Y3Al5O12 (YAG)m composite by introducing grains of another phase (tetragonal zirconia) into the alumina matrix. The sintering of such a com-position demanded temperature conditions which did not exclude the possibility of yttria atom diffusion betwe-en the garnet and zirconia grains. This phenomenon strongly influenced the phase composition of the final sin-ters. The paper discusses the microstructure of the sinters. The influence of the starting composition and sintering conditions on the final phase composition and selected mechanical properties of sinters were investiga-ted.

Among sound insulating materials used in the automotive industry, multilayer systems consisting of foams, nonwovens, mats, knitted fabrics or porous panels in different combinations are very popular. These materials can be replaced by fibre reinforced composites. These composites can be good sound absorbing materials even at low thickness. One way to increase sound absorption is to form a composite with an optimal structure and surface topography. In this work, the investigations concern the sound absorption by thermoplastic composites with surface asymmetry. The influence of surface asymmetry of thermoplastic composites on their sound ab-sorption coefficient was studied. The first kind of asymmetry concerns the structure of the composite surface, i.e. plastic and fibrous structure. The second kind of asymmetry concerns the topography of the composite sur-face, i.e. the one side of the composite surface is smooth and on the opposite side it is characterized by some re-lief. The sound absorption coefficient was measured for different sample orientations to the sound wave to as-sess the significance of the surface asymmetry and to indicate a more favourable composite side from the sound absorption point of view. Generally, both the surface structure asymmetry and surface topography asymmetry influence the sound wave behaviour and consequently increase the composite sound absorption.

This work concerns the biological and morphological assessment of poly(lactide-co-glycolide)/silver nanopar-ticle (nAg) composites prepared by the slip-casting method. Due to the significance of the bactericidal proper-ties of such materials, antibacterial activity against Gram-positive - Staphylococcus aureus and Gram-negative - Escherichia coli was evaluated by means of the surface deposition method. By inductively coupled plasma mass spectrometry (ICP-MS), it was possible to evaluate the amount of released silver ions and to determine their im-pact on the surrounding environment of bacteria. The material microstructure and dispersion of the modifier phase were estimated by using electron scanning microscopy with elemental analysis in micro-areas (SEM+EDS). The roughness and Theta angle measurements allowed us to define the surface character of the investigated materials. The tests of antibacterial efficacy proved that nanosilver-modified composites have bac-tericidal activity against the tested bacteria. The antibacterial efficacy of the tested materials depends on the amount of modifier phase (nAg). Along with an increasing volume fraction of modification phase, a different degree of the homogenization process was observed as well as a reduction in composite homogenization, a roughness increase and Theta angle decrease. At the same time, the composites showed higher wettability. Spectrometric analysis showed that the amount of released silver ions depends on the amount of nanoparticles present in the polymer matrix.

Silver-based composites can be divided into two types: type 1 uses a pure element or carbide as the dispersed phase; type 2 uses oxides as the dispersed phase. In this work was shown the combined effect of small additions of oxides with tungsten. Attempts have been made to describe the influence of production process parameters on the microstructure and properties of Ag-W-TiO2 composites. The compositions of the powder mixtures are Ag + 10% W + 1% TiO2, Ag + 20% W + 1% TiO2, Ag + 30% W + 1% TiO2. The powder mixtures were prepared by tumbling in a Turbula type mixer. The mixtures were then subjected to a double-press/double-sinter process. The studies show that a nearly fully-dense material made of silver, tungsten and TiO2 powders cannot be achieved by double pressing and double sintering. The relative density near 90% of the composites was achieved. The electrical conductivity and bending strength of Ag-W-TiO2 materials decrease with tungsten content, but the hardness of Ag-W-TiO2 materials increase with the amount of tungsten. The Ag + 10% W + 1% TiO2 and Ag + 20% W + 1% TiO2 materials studied in this work also show relatively homogenous distribu-tion of the tungsten and TiO2 additions.

The paper describes the sol-gel method for preparing nanocomposites from the TiO2-SnO2 system with various chemical compositions. The obtained nanopowders are characterized by a significantly expanded specific surfa-ce area (SSA ~ 100 m2/g), which suggests low particles agglomeration and undoubtedly has a beneficial effect on the application of the obtained nanopowders in the production of resistive sensors for gas detection. The cry-stallites sizes estimated with use of XRD (Dhkl ~ 8 nm) are similar to those calculated based on specific surface area measurements (DBET ~ 15 nm). Moreover, the paper examines the spectral dependence of the diffuse re-flection coefficient Rdiff(lambda) of the obtained nanocomposites.

An attempt has been made to prepare Al₂O₃/Ni composites with 1 vol.% metal particles by the gelcasting method. Alumina matrix composites with an addition of nickel particles, already used in industry, are produced by various methods. Unfortunately, there is a problem to obtain elements of a complex shape characterized by a uniform distribution of metal particles in a ceramic matrix. For this reason, the authors have attempted to apply the gelcasting method to produce an Al₂O₃ +1 vol.% Ni composite. The electrokinetic properties of the composite slurries and the influence of the presence of nickel have been studied. The microstructure of green and sintered samples were examined with a scanning electron microscope. Selected physical properties of the composite have been described. The material in the green state was characterized by a density of about 57%, and 97% after sintering, of the theoretical density. Nickel particles were uniformly distributed in the ceramic matrix. The performed studies have confirmed the possibility of using the gelcasting method to produce an alumina-nickel composite.

This study examines how the fluidizing time influences the thickness and decorative properties of a protective coating created by the fluidization method. We have made two types of coatings: polyethylene and a composite (with polyethylene matrix and SiC particle reinforcement). The work, responding to the market demand for new attractive-looking materials, meeting certain preset criteria, such as coating thickness, is part of research into the selection of protective-decorative coatings for elements working in the natural environment, subject to UV radiation, wind and rain.

Composites containing nickel nanoparticles dispersed in a ceramic polycrystalline matrix are widely utilized materials for different applications. They are utilized in ceramic matrix/metallic additive composites due to their profitable influence on both the mechanical (grain size growth control, stress relaxation on crack tip by plastic deformation) and functional properties. A zirconia/nano-Ni composite is an important material for solid oxide fuel cell electrodes possessing unique electrochemical properties. Another composite composed of alumina and nano-Ni is a widely investigated structural material showing excellent mechanical properties. The paper presents an innovative pro-ecological method for synthesizing nickel nanoparticles to be used in ceramic matrix/metal particle composites, which could be used as an alternative to traditional methods. The proposed biochemical syntheses minimise or even completely eliminate the amount of produced waste and could be implemented as sustainable processes accepting the basic principles of “green chemistry”. The suggested method enables precise size control of the created nanoparticles and at the same time offers numerous advantages in comparison to conventional methods.

The effects of applying the stir casting method to fabricate composites with an Mg-Zn-Zr-RE magnesium alloy matrix reinforced with short carbon fibers are presented in the article. The experimental procedure carried out in industrial conditions was described. Carbon material in the form of short staple fiber granules obtained from chopped/cut carbon roving was used. The procedure of suspension fabrication and casting in ceramic and steel moulds was described. The possibility of obtaining casts of different size and shape which can be a semi-product for die casting technology has been shown. Additionally, the microstructure and mechanical properties of the obtained material were characterized.

The aim of the study was to develop a laminate composite that can be an analog for St3S steel in the case of corrosion problems and excessive product weight. E-glass fibers in the form of mats and fabrics with different reinforcement direction, unsaturated polyester resins, and basalt woven fabrics with a grammature of 180 g/m² were used in the study. Polyester laminate composites of 300x200 mm were manufactured using the vacuum assisted resin transfer molding method. The mechanical properties of the laminate composites in the form of plates were compared with the mechanical properties of the St3S steel serving as a reference material. Selected glass fiber-reinforced polyester composites with the best mechanical properties were additionally modified with basalt fabric. The flexural strength, elasticity modulus and work up to fracture were determined in the three-point bending mode. The values of the mechanical parameters of the composite samples were compared with the mechanical properties of St3S steel. The highest elasticity modulus of the laminate samples was found for the composite reinforced with a unidirectional glass fabric, while the maximum flexural strength was attained by the composite samples reinforced with three and four directional fibrous reinforcement. Their differences amount to several percent. The composite samples representing the best strength properties were further modified using a fabric made from basalt fibers. The use of hybrid fiber reinforcements (glass fiber, basalt fiber) allows for an over 20% increase in the flexural strength of the composite samples. Comparable strength characteristics to the steel samples were achieved. The flexural strength of the hybrid composite samples was 415 MPa, and 429 MPa for the St3S sample. The hybrid laminate composite with basalt woven fabric has a distinctly higher work up to fracture value in comparison with the unmodified laminate composite related to the same cross section unit.

The additions of 5÷10 wt.% TiC to WC-Co industrial composites substituting WC were consolidated using either the Hot Isostatic Pressing (HIP) method at the temperature of 1320°C and pressure of 250 MPa, or using the Spark Plasma Sintering (SPS) method. The latter samples show a hardness increase from 1050 HV (without TiC) up to 1330 HV at 5% TiC. A larger addition of 10% TiC allows one to obtain a similar hardness increase as in the case of the 5% addition. A higher hardness of 1570 HV was observed for samples consolidated using HIP, which can be explained by the higher consolidation pressure of 1500 bars and temperature of 1350°C leading to a lower porosity. The crack formation behavior allowed the authors to determine the fracture toughness, K_IC, in the range of 10.9÷11.2 MPam^1/2 for the samples containing 0÷10% TiC. Three phases were identified using the X-ray diffraction method, as well as scanning and transmission electron microscopy. The major identified phase is WC particles separated by a narrow layer of Co and are accompanied by single particles of TiC. It indicates that TiC do not form a common solid solution with WC as also confirmed by EDS chemical analysis, which was suggested in literature.

The homogenous distribution of reinforcing phases in a liquid metal matrix determines the final properties of composite elements fabricated by the casting of a suspension. Ensuring not only a proper temperature and stirring conditions during suspension preparation, but also a relatively short time between the end of mixing and the start of suspension pouring into moulds is critical. In the article, investigations focused on the migration of glassy carbon particles (GCp) in two melted magnesium alloys, Mg₃Al and Mg₂ZnZrRE, were presented. The composites previously obtained by the stir casting method were remelted at the temperatures of 610, 640, 690 and 730°C (time 30, 60 and 90 min) and finally cooled at a temperature of 20°C. The particles segregation on the macro scale was analyzed on a longitudinal section of the obtained samples. It was revealed that both types of suspensions were stable at 610 and 640°C but at 690 and 730°C, a loss of stability was observed. In spite of the slightly less density of the glassy carbon than the applied magnesium alloys, the type of segregation was different and depended on the alloy chemical composition. In the suspension of Mg₃Al-GCp, particle migration to the crucible top was observed only, while in the Mg₂ZnZrRE-GCp suspension, two zones with a high particle concentration were formed, separated by a zone of pure metal.

The preliminary results on the application of cold chamber pressure die casting for fabricating a magnesium matrix composite with glassy carbon particles were presented. For small-sized composite casts, processing a suspension obtained by remelting of composite ingots was applied. Those ingots were previous fabricated by mechanical stirring and gravity casting. Composite casts of a mass of 14 g, complex shape and homogenous particles distribution, without cast defects were obtained. Their macrostructure, microstructure and mechanical properties were characterized. The usefulness of pressure casting for the fabrication of particulate magnesium matrix composite casts was revealed.

The aim of this paper was to characterize the microstructure, especially the morphology of NiAl₂O₄ spinel phase in Al₂O₃-Ni composite system. The composites were prepared from the powder mixture contains: 90 vol. % of Al₂O₃ and 10 vol. % of nickel powder. Two series of samples were prepared: Series I with addition of nickel powder of average particle size 8.5 µm and Series II with addition of nickel powder of average particle size 1.5 µm. The presence of the spinel phase in composites was confirmed by both X-ray phase analysis and SEM observations. All tested samples were characterized by homogeneous distribution of NiAl₂O₄ phase in the whole volume of the material. The spinel has on oval shape with characteristic void inside. Two areas of spinel phase were identificated. The inner part is compact and consisted of large grains of spinel. In contrast, the outer part is porous and consisted of smaller grains of spinel. In aim to describe the spinel morphology the stereological analysis was done. Results showed that there is no evident influence of Ni initial grain powder size on the spinel formation and morphology. Formation of the spinel retarded the densification of the composites of Al₂O₃-Ni system.

In this work, a novel approach of thermal non-destructive testing of composite structures is presented. Among the widely-known pros and cons of Active Infrared Thermography (AIRT), there is still space for its cognition and development. In general, AIRT is based on heat transfer which is changed by the presence of subsurface flaws, variation of thicknesses, corrosion etc. Internal defects disturb normal heat diffusion within the material due to different thermophysical properties, and the result is variation of the amplitude and phase of the response signal on the surface of investigated objects. Typically, external excitation is performed by different heat sources (i.e. halogen lamps). Application of a thermoelectric module as a heat flux activation source presents clear disadvantages in terms of versatility, but it creates new possibilities of testing components which cannot be heated e.g., due to thermal expansion or space limitation for the excitation source. In addition, this approach provides quick measurement. The investigated samples are previously cooled down by the thermoelectric module, and then they are exposed to a higher ambient temperature. An infrared camera monitors the surface temperature variation both during the cooling and heating stage in order to reveal subsurface flaws. The main aim of this work is to examine the effectiveness of Cooling Down Thermography (CDT) to detect artificial delaminations in composite plates.

The number of structures made from multi-layered composite materials increases every year. Some of these structures include different cutouts, which result from the manufacturing process or are needed for maintenance. This kind of discontinuities are the source of stress concentrations, which cause the nucleation and evolution of various forms of damages in composite materials. The problem of the damage becomes particularly important when the structure is subjected to cyclic loads. The present work concentrates on the investigation of the strength evaluation for rectangular composite plates with internal holes of different shapes. Numerical results are presented for circular, elliptic and square (with rounded corners) holes placed in the centre of a plate, which is subjected to bi-directional tension pressure imposed along the outer edges. It is assumed that the stacking sequence is symmetric with respect to the middle surface of the structure. The considered plates are made from an angle-ply laminate, which consists of the twelve layers with a fiber orientation angle ±θ, for example [±5°, ±5°, ±5°, ±5°]S, where 's' denotes the symmetry. The fiber orientation angle θ is studied in order to find the maximum strength of the considered plate. The solution is sought from the following discrete values, namely [0°, 5°, 10°, 15°, … , 90°]. The numerical calculations are performed with the use of the multipurpose finite element code ANSYS 12.1. In order to estimate the static strength of the structure, the linear (admissible stress) first ply failure criteria are applied. The influence of the geometry of the plate and the cutout on the optimal solution (fiber orientation angle ±θ) is also investigated. It is assumed that the ratio of the area of the analyzed plate and the hole is constant for the different shapes of holes. Simulations are performed for the two different materials, where the ratio of Young's modulus E₁, E₂ equal, respectively, E₁/E₂ << 1 (anisotropy) and E₁/E₂ ≈ 1 (quasi-isotropy).

One of the most popular steels which have been used for tools in the hot metal extrusion process is AISI type H13 hot work tool steel. Although this steel has relatively good properties - wear resistance and hot toughness - it is no longer completely satisfactory because new extrusion materials place higher demands on extrusion tooling, and H13 type steel in its current form is not optimal. The paper presents the proposition of improving the properties of H13 type steel by introducing hard ceramic particles as reinforcement to the structure. Such composites consist of a modified H13 steel matrix and TiC par-ticles of 0, 10, 20 and 30 volume percent. The composites were manufactured by the powder metallurgy method. The atomized matrix powder was mixed with a TiC powder using a Tubular mixer for 60 min. The mixed materials were consolidated by Hot Isostatic Pressing (HIP). Prior to the HIP process, the powder materials were placed in a steel can. The conditions of hot isostatic pressing for the modified H13 tool steel matrix composites were: temperature 1150ºC, time 4 hours and pressure 100 MPa. Particle reinforced metal matrix composites are difficult to machine using conventional manufacturing processes due to high tool wear caused by the hard reinforcement, even those tools which are made of cemented carbides. One of the best methods of machining of composite dies is sink electro-discharge machining EDM or wire electro-discharge machining WEDM. This work concerns the investigation into the machinability of Titanium Carbide (TiC) particle reinforced modified H13 steel using wire electro discharge machining (WEDM). WEDM cutting was conducted using a machine equipped with a RC type relaxation generator. The dielectric used in this experiment was deionized water. As the tool material, brass wire with a diameter of 0.25 mm was used. To compare, wrought H13 steel was also machined. The machining parameters such as pulse time and load voltage were varied in order to optimize the metal removal rate and surface integrity. The obtained results indicate that MMCs can be machined using WEDM although the metal removal rates are lower compared to conventional machining processes. It is shown that the surface roughness increases with higher discharge energy and decreases with the volume fraction of the reinforcement. The optimum machining rate considering the roughness and cutting rate, was when the pulse on-time is at 1.5 µs, pulse off-time at 10 µs and load voltage at 122 V.

In this paper, the influence of a glycerol derivative (glycerol monoacrylate) synthesized by the authors on the dilatant effect of shear thickening fluid was investigated. It was assumed that the monomer synthesized from acrylic acid and glycidol, owing to the presence of two hydroxyl groups, allows one to enhance the dilatant effect of the investigated slurries by creating a three-dimensional network between the powder particle and dispersing agent. The dilatant effect was examined with respect to the solid loading and molecular weight of the dispersing agent. As the ceramic powder, a nanosilica with an average particle size of 14 nm was used. Poly (propylene glycol) of a molecular weight of 400 and 725 g/mol played the role of dispersant. The solid loading was changed from 12 to 15 vol.%. The measurements showed that by applying even a small amount of glycerol monoacrylate (0.5 wt.%), it was possible to enhance the dilatant effect of the investigated slurries. It was also observed that by increasing the solid loading and/or using a poly (propylene glycol) of a higher molecular weight, it was possible to increase the critical viscosity even threefold. Furthermore, the rheological properties of the slurry return to the initial state when the external force ceases. The influence of temperature and quantity of impacts also were investigated. The measurements showed that by increasing the temperature of the shear thickening fluid from room temperature to human body temperature, resulted in a decreased dilatant effect of the slurry. However, the onset of shear thickening and critical shear rate shifted to higher values of shear rate. Moreover, widening of the dilatant jump was observed. Similar results were obtained as a result of the using the fluid several times. The studies have shown that with each successive impact, the dilitant effect decreases.

The paper presents the influence of a hybrid composite structure containing two reinforcing phases i.e. porous, spherical Al₂O₃ ceramic particles, coated with glassy carbon film which carries out the function of solid lubricant. This composite is manufactured by a new method developed in 2013, which consists of three stages i.e. pre-form manufacturing from porous foam by means of gelcasting, foam saturation with a glassy carbon precursor and its pyrolysis, followed by the infiltration of the pre-form coated with glassy carbon by a liquid alloy. The new method helps to obtain composites with homogenous glassy carbon distribution which improves their tribological properties. The presence of aluminum oxide increases the hardness locally whereas the presence of glassy carbon mitigates the shear strength. Comparative tribological studies of a composite with an AC-AlCu3Mg1 matrix alloy containing 10% Al₂O₃ and the hybrid composite in which aluminum oxide spheres have been coated with glassy carbon, both sliding against GJL-300 cast iron in air, confirmed the positive influence of carbon on both the friction coefficient and wear. The friction coefficient at a sliding speed of v = 2.5 m/s and unit pressure p = 2 MPa after wearing-in of the sliding surfaces is 0.08÷0.12 for the composites with glassy carbon and 0.25÷0.32 for the composite which contains only ceramic spheres.

Substantial progress in the field of materials used for medicine has be observed in recent years, driven by the higher demand for these types of materials. Promising prospects are offered by composite materials that allow for unlimited modelling of the properties in materials used for specific medical applications. The focus of the investigations presented in this paper is placed on metallic-ceramic composites based on a titanium alloy matrix (Ti-6Al-4V) with a 20 wt.% addition of aluminium oxide (Al₂O₃), hydroxyapatite ceramics (Ca₁₀(PO₄)₆(OH)₂) and YSZ (zirconia stabilized with 8 wt.% yttria Y₂O₃) obtained using the spark plasma sintering method. The specimens were compressed at 35 MPa and sintered in a shielding gas (argon) medium at the temperature of 1000°C in an SPS HP 5 apparatus manufactured by FCT for 25 min. The obtained composites were subjected to microstructural analysis using an Axiovert light microscope and X-ray quality analysis using a D8 DISCOVER Bruker diffractometer. Hydrostatic weighing in deionized water according to the PN EN ISO 2738: 2001 standard was also used to evaluate the density (apparent and relative), porosity (open and total) and water absorption capacity. The topology of the surface of the metallic-ceramic composites was determined using a Hommel T1000 profilometer. The mechanical properties (microhardness) were measured using a semi-automatic microhardness tester (FM-7, FutureTech) with a Vickers indenter at a load of 100 G. The resistance to wear was evaluated by means of a ball wear testing stand. In this study, Ti6Al4V/HAp(ZrO₂, Al₂O₃) composites were prepared using spark plasma sintering (SPS) to obtain highly compact composites. The aim of the study was to evaluate the ability of spark plasma sintering to obtain metallic-ceramic composites based on titanium alloy with an addition of inert ceramics and bioactive ceramics for medical applications.

This article presents the results of studies concerning the production technology and properties of 316L-HAp composite materials sintered at temperatures of 1000 and 1100°C with compaction pressures of 5, 25, and 50 MPa. The spark plasma sintering method (SPS) was applied for the purpose of producing these materials. 316L-HAp composites characterized by densities ranging from 5.45 to 6.01 g/cm³ were the final products of the applied process. The results of absolute porosity measurements are discussed. It is shown that as sintering temperature and compaction pressure increase, so does the sinter's apparent density and compression strength, although an Rc value that is lower by 8% is observed for sinters produced at a temperature of 1100°C compared to those produced at a temperature of 1000°C. Hardness decreases as sintering temperature increases and reaches the highest values in sinters produced with a compaction pressure equal to 25 MPa.

Composite γ-Ni+γ’ coatings on an iron substrate were developed by the conversion of Ni+Al electrodeposits with dispersed Al particles in an Ni matrix. The conversion was made by vacuum annealing at 900°C for 3 h under a uniaxial pressure of 1 MPa and full-density composite coatings were obtained. A nickel interlayer was successfully employed to block the mutual diffusion between the iron substrate and aluminium and therefore hard and brittle Fe-Al intermetallics were not formed. The oxidation resistance of as-plated Ni and γ-Ni+γ’ composite coatings at 1000°C was compared. After 100 hours at 1000°C, a mass gain of oxides for the γ-Ni+γ’ coating was about 7 times less than for the nickel coating. The γ-Ni+γ’ coating follows parabolic oxidation kinetics, which implies that oxidation is bulk-diffusion controlled. SEM/EDS and XRD characterisation showed that during oxidation, a thin continuous Al₂O₃ layer is formed below the matrix of an NiAl₂O₄ spinel. The wear mass loss of the γ-Ni+γ’ coatings was found to be about 3 times smaller than the as-plated Ni and Ni+Al coatings. Moreover, the γ-Ni+γ’ coatings oxidised for 20 h, containing very hard and wear-resistant Al₂O₃ particles, show the smallest wear mass loss of all the tested materials.

Non-contact measuring techniques are nowadays widely used in many applications from industry to the laboratory testing of advanced materials. The present paper is dedicated to the laser measurement scanning technique being one of the 3D active vision measurement non-contact systems. In order to analyze the deformations of a composite structure, 3D virtual models of an unloaded and loaded composite sample are created from 3D scanning data. The results of the deformation analysis are presented in the form of contours of the 3D deviations. Additionally, a comparison between the virtual images of the intact and delaminated areas of the analyzed composite structure is presented.

This paper presents the tribological characteristics of friction materials manufactured for a high loaded friction point. Composite powders containing 1% carbon nanotubes or 5% glassy carbon particles were produced by high energy milling in planetary mills. High energy during powder preparation led to reinforcement particle fragmentation up to sizes between 0.1÷2 µm. Furthermore, mechano-chemical bonding between the reinforcement and the Al particles used as the matrix was obtained during this process. As a result of the pressing and sintering processes, composite materials with homogeneous reinforcement (SiC) or heterogeneous reinforcement (SiC with addition of 1 wt.% multiwalled carbon nanotubes (CNT) or 5 wt.% glassy carbon particles) were manufactured. The properties of the obtained composite materials were measured during tribological tests at room temperature (25°C) and high temperature (450°C). The tribological research was conducted by the ball-on-disc method, at a distance of 250 m, with a load of 10 N and sliding speed of 0.1 m/s. The analyses of the friction coefficient and wear results revealed the desirable influence of the carbon components especially in increasing the average value and stabilization of the friction coefficient, particularly at room temperature. Moreover, the carbon additions led to a decrease in wear in comparison to the composite reinforced with SiC particles only. The changes in the wear level and friction coefficient value are a result of the differences in the predominant wear mechanism observed between the friction surfaces of the composite materials at room and high temperatures.

The paper presents the study of multilayer nanocrystalline Ni/Cu coatings produced by the electrocrystallization method on a carbon steel S235JR substrate. Three variants of multilayer nickel/copper coatings of various thicknesses and quantities of the individual layers of nickel and copper were tested. The coating properties were characterized using the following research techniques: X-ray diffraction (XRD), transmission (TEM) and scanning (SEM) electron microscopes, optical microscopy and Vickers microhardness measurements. The paper presents the results of the structure, morphology, surface topography and microhardness measurements of multi-layer nanocrystalline Ni/Cu composite coatings. The produced coatings have a nanocrystalline structure, compact structure, good adhesion to the substrate and a uniform thickness over the entire coated surface. The thickness of the single layers of nickel and copper has an effect on the hardness of the multilayer Ni/Cu composite coatings.

This paper presents the results of studies on the electroless deposition of Ni-P/nano-SiO₂ composite layers on pre-treated polymeric bases (PET polyester Mylar A type) and on carbon fibers (24k fibers with 7 µm Tenax rovings). The Ni-P matrix was deposited from a bath consisting of NiSO₄ 0.1 M; NaH₂PO₂ 0.2 M; glycine 0.21 M, with a pH = 7.5÷8.5 and thiourea added as a stabilizer, as well as cetyltrimethylammonium bromide as a surfactant. Silica powders (Sigma, grains 7 and 14 nm) were added in amounts of 10÷30 g/l, with ultrasonic homogenization of the suspension or by using a homogenizor. Under the applied experimental conditions, the deposition of composites with two types of silica on two types of substrate was carried out. The deposition was performed in the temperature range of 60÷70°C, during 5÷60 minutes, while the samples rotated at 1 rpm and the suspension was agitated with a stirrer. The composition of the deposited layers was determined by chemical methods and their surface morphology was investigated using SEM. Under the applied conditions, Ni-P/SiO₂ layers of a thickness within 120÷710 nm, an aluminium oxide content up to 17.3 wt.%, and 2÷3 wt.% phosphorus were obtained.

In this study, fatigue damage progress is analyzed both theoretically and experimentally. Cyclic loading causes damage, reducing the strength until the material can no longer sustain even service loading. The theoretical analysis is associated with the definition of the damage parameter. The experimental analysis is mainly devoted to the consideration of two structural elements, i.e. a rectangular composite plate (made of glass fibre/epoxy resin) with a centrally located circular hole subjected to cyclic tensile stress and a square plate (made of aramid fiber/epoxy resin) subjected to shear loading. The experiments demonstrate scattering of the results. Fuzzy set analysis has been proposed in order to estimate the uncertainty in evaluation of the critical number of cycles corresponding to the final fatigue damage.

Magnetorheological characterization of a synthesized MRF and ballistic performance of a MRF-composite material with high-strength textiles as Kevlar and Dyneema, are presented. The ballistic performance of the investigated structures under a Parabellum 9 mm projectile with a velocity of 360 m/s, on the basis of deformation depth in backing clay and number of pierced layers was determined. The targets with MRF demonstrate a 30% reduction in depth of deformation when comparing to the neat samples. On the other hand, implementation of the MRF to the structures of the high-strength materials caused a twofold increase in the overall target weight. At the same time, the inherence of the MRF in the structure of the composite samples does not affect the number of damaged layers. This result indicates that the absorbing mechanism of the MRF is rather limited to residual energy absorption under the impacting projectile.

Nickel coatings produced by plating processes are mainly used for decorative purposes and as a material that protects the substrate from corrosion. The incorporation of a reinforcing phase of alumina in a ductile nickel matrix allows for improved tribological and corrosion properties. The aim of this study was to investigate the effect of the process parameters on the structure of Ni/Al₂O₃ composite layers produced by the electrochemical method. The study included composite layers of a microcrystalline and nanocrystalline Ni matrix and micrometric and nanometric particle size disperse phases of Al₂O₃. The layers were deposited in a Watts bath modified by a nickel grain growth inhibitor, at a current density of 5 A/dm². In order to ensure uniform co-embedding of the disperse phase particles with the nickel matrix and to produce a stable suspension, a cationic surfactant was also used. The completed studies have shown that addition of the nickel grain growth inhibitor significantly affects the reduction of the nickel crystallite size. The particle size of alumina affects its content and distribution in the Ni/Al₂O₃ composite layer. Both, the grain size of the nickel, as well as the amount and type of built-in phase affect the microhardness of the examined nickel and composite layers.

During the last few years, many scientists and industries have become interested in developing new materials which would maintain good mechanical properties and low density comparable with aluminum alloys. This can be observed predominantly in the aircraft or aerospace industry. Fiber metal laminates (FML) are a new kind of composite, particularly the Glare^® type laminate, which consists of aluminum and a glass/epoxy composite. FML combine both the good characteristics of metal such as ductility and durability with the benefits of fiber composite materials such as high specific strength, high specific stiffness, good corrosion resistance and fatigue resistance. In this paper, an FML consisting of aluminum and glass fiber/epoxy layers has been introduced. The FML were produced by the autoclave technique. The aluminum sheets were special prepared with chromic acid and sulphuric acid aluminum anodizing. Two combinations of fiber configuration were selected: Al/[0]/Al and Al[0/90]/Al. The structure characterization after bending tests is shown and discussed. Microstructural analysis has been carried out using an optical microscope. The three point-bending tests were conducted according to standard specifications. Preliminary studies have shown that the metal layers in the laminates and the composite polymer layer, particularly in the bend area in the laminate, have a significant impact on the nature of the damage. Laminate destruction indicates the complexity of the degradation process of these materials. The orientation of the reinforcing fibers has an influence on the degree of destruction of the laminate structure which may have a decisive effect on the ability of forming laminates. An important factor influencing the properties of the laminate as a whole is to provide high adhesive properties of the composite-metal connections.

Composite structures built of para-aramid fabric and shear thickening fluid (STF) are developed in the light of their potential application in smart body armour. The study reports on the rheological behaviour of nanosized silica suspensions. Depending on the oligomer chemical structure and molecular weight, we observe different behaviour under shear stress. The STF composed of PPG400 and containing various volume fraction of FS showed good time stability. The compositions containing 6.5 and 11.7 vol. % of silica maintain their rheological properties, although the composition with the highest concentration of solid phase lost about 20% of its maximum viscosity value after 40 days in a closed vial. The addition of colloidal shear thickening fluids to para-aramid woven fabric (Twaron^® CT709) showed enhanced ballistic penetration resistance of the elaborated system for Parabellum 9mm bullet.

The paper concerns the activated sintering of boron carbide based materials. The work shows the influence of introduced Cr₃C₂, CrSi₂, Cr₃Si modifiers on the sintering of commercial boron carbide. A high-temperature graphite dilatometer was used in order to investigate boron carbide sintering with various additives. The shift of the onset and endset sintering temperature of different sample compositions was determined. The influence of chromium compounds on sintering was explained by XRD phase analysis. The phase changes in the sinters vs. increasing volume fraction of the additives were made. The same analyses were made on samples heat-treated close to the onset sintering temperature.

The work presents the technology and investigation results of ferroelectric-ferromagnetic composites based on ferroelectric powders of the PZT type and ferrite. The ferroelectric powder comprised two PZT type compositions: Pb_0.84Ba_0.16(Zr_0.54Ti_0.46)O₃ + 1.0%at. Nb₂O₅ (PBZTN) and Pb(Zr_0.51Ti_0.49)O₃ + 0.2%at. Bi₂O₃ + 0.03%at. Nb₂O₅ + 0.06%at. MnO_{2 (PZTBNM). The initial constituents for obtaining the PZT type powders included oxides: PbO, ZrO2, TiO2, Nb2O5, Cr2O3 as well as carbonates: barium BaCO3 and strontium SrCO3. In the PZT-ferrite composites, the synthesized ferroelectric powder constituted 90%, whereas the ferrite powder (Ni0.64Zn0.36Fe2O4) was 10%. Temperature examinations of the internal friction (IF) of the PZT-ferrite type composites, which belong to non-destructive methods of material examination in mechanical spectrometry, and also measurements of the dielectric properties were performed. The IF method enabled the authors to determine mechanical properties such as mechanical losses or value of Young's modulus in a broad range of temperatures. For both the investigated composites, an increase in mechanical losses Q^–1 and decrease in Young's modulus Y with an increase in temperature were observed. At the phase transition point connected with an electric sub-system change while changing from the ferroelectric to paraelectric state, a rapid increase in Young's modulus Y was observed. It was confirmed in further investigations of dielectric properties (T) i tan(T).}

This work presents the results of studies concerning the production and characterization of Al-SiC composite materials with a 20 and 25% volume fraction of reinforcing phase particles. The spark plasma sintering method (SPS) was applied for the purpose of producing these materials. The final product of the applied process was Al-SiC composites characterized by a density from 2.70 to 2.72 g/cm³. The results of effective porosity and total porosity measurements are discussed. It was proven that as the content of hard ceramic particles increases in the composite, its apparent density, hardness, and compression strength increase with a simultaneous reduction in tensile strength. For example, the performed tests showed that the composite with the 25% silicon carbide content exhibited the greatest hardness (81.2 HBW 2.5/62.5) and compression strength (315 MPa).

The article presents the results of studies on the mechanical and tribological properties of polymer composites intended for the regeneration of sliding machine elements. Chemically cured epoxy resin Epidian 5 constituted the composites’ polymer warp. Fe powder with a define content of grains and obtained by means of reduction was used as a basic filler, whereas solid lubricants of a layered structure - graphite and molybdenum disulfide - were used as the sliding additives, and polyaramid fibres in the form of pulp - as a fibrous filler. Three series of composites with different qualitative and quantitative compositions were prepared with the addition of lubricating agents in the amount varying from 10 to 30 parts by weight in a single or combined system. The composites were crosslinked with aliphatic polyamine (triethylenetetramine), and the crosslinking process was conducted at room temperature. Once the composites were cured, their mechanical properties (i.e. resistance to compression and tear, and the module and deformation at the time of bending) were checked with the use of an Instron machine for endurance tests. The tribological characteristics of the composites in dry friction conditions were determined with a T-05 roll-block type tribotester, in which a roller with a composite layer deposited on its surface played the role of a model tribological system. A steel block, on the other hand, played the role of a counter sample. The friction and wear tests were conducted at the constant speed of slide of 0.1 m/s and changeable pressures of 0.9 and 1.5 MPa. Based on the obtained friction and wear properties and the results of investigations in which scanning electron microscopy (SEM) was applied, it was concluded that the best results are displayed when solid lubricants of a layered structure are jointly applied.

In the article, an approach for damage characterization in composite aerospace structures for the linear acoustic non destructive evaluation technique is presented. The damages which affect the structural integrity of such components among others are: disbonds, delaminations and foreign object inclusions. One of the significant damages which may occur during structure operation is low energy impact damage (BVID - Barely Visible Impact Damage). BVID may decrease the stiffness of the component due to the creation of internal damages resulting in impact energy dissipation across the material. In the paper an approach for their diagnostics is presented. The approach is based on structure integrated PZT piezoelectric sensors. The application of such sensors enables acoustic and local distortion fields propagation based on the physics of small displacements in continuous media. This can be affected by local geometry changes caused by BVID which opens an opportunity for their detection. The signal processing methods which may enable damage detection and their classification are presented in the article. The results of low energy impact detection based on the PZT sensor network approach as well as their full characterization using classical NDE are also provided.

Since today's petrochemical industry is able to explore the seabed at the level of 3000 m, there is also a need to provide reliable, but cost effective enclosures for the respective technical equipment. This paper gives in-depth analysis of the design aspects for fiber reinforced pressure chambers, which are installed in the subsea environment. A chamber structure consisting of a metal liner and fiber reinforced composite is considered. Two theoretical models: for a generalized orthotropic material and for a laminated composite are recalled and used in the analytical study of the vessel. Finally, a structure optimization procedure is introduced and a verification example is provided.

In the article, three different type II additives (fly ash, silica fume and slag) were used in order to improve the adherence of polypropylene fibres to cement mortar. Estimation of the level of fibre adherence to the cement matrix change was conducted on the basis of mechanical research of the composites, as well as observation of the interfacial transition zone between the fibres and cement paste in scanning electron microscopy. It was shown that the mechanical properties of cement composites modified with polypropylene fibres strongly depend on the type of pozzolanic additive and compactness of the interfacial transition zone between the fibres and cement paste. The obtained values of fracture toughness of the cement composites proved that during the whole research period (180 days), the presence of 0.5 vol.% polypropylene fibres, regardless of the cement matrix applied, improves the fracture toughness of the cement matrix. However, two ranges of reaction between the cement matrix and the fibres were observed; the first up to 56 days of hardening, where the fibrocomposite properties depend, besides the fibre properties, on clinker fine-crystalline phases of cement paste. The second one - after 56 days of bonding, where the composite properties depend mostly on the pozzolanic and hydraulic additives.

The usage of ceramic materials in applications endangered by intensive cavitation could limit erosion phenomena. In the presented work, cavitation erosion resistance of commonly used oxide phases (-alumina, tetragonal zirconia) in structural application were investigated. Volumetric wear of both materials was compared to the wear rate of FeAl48 alloy. Both oxides were more resistant for cavitation than intermetallic phase. Observations by means of SEM technique showed that surface destructions run in a similar way for both investigated oxides. The degradation proceeded by removing of the whole grains from sintered body. However, in the alumina grains were removed from a wide area, opposite to the zirconia material, which was degraded in limited, ribbon-like areas. In this case destruction reached deeper than only the one grain into material.

Abstract Fibre Reinforced Polymers (composites) are widely used in the aerospace industry due to their excellent quasi- static mechanical properties in relation to density. However, it is known that polymer composites do not have good resistance to dynamic loads, especially to low-velocity impact phenomena, which is one of the most important issues for composite structures, particularly in aerospace due to the effect it has on material structures. The purpose of this study was to investigate the differences in polymer composite behavior between low-velocity impact and the similar (the same boundary conditions) quasi- static indentation. The composites used in this study were: Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) manufactured by the autoclave method (materials used in aerospace technology). Impact tests were carried out according to the ASTM D7136 standard. Quasi-static indentation was performed according to the ASTM D6264 standard. After the tests, the samples were subjected to non-destructive and microscopic testing methods to investigate the damage size and failure character. It was noted that low-velocity impact causes significant damage to both kinds of composite structures, while the quasi-static indentation under the same impact force level results in some internal degradation of the laminate structures (barely visible damage). However, the size of it is extremely different to the case of low-velocity impact. The failure types of composite structures after static and dynamic loads are similar. The major failure type in composites after static and dynamic loads are matrix cracks, delaminations, and in the case of impact fibres-cracks. To obtain similar damage character and size (as in the impact effect) in the composite structure on account of quasi-static indentation, a much higher force level in comparison to dynamic loads is necessary.

The yield and flow stress data for an Al-10% SiC composite and for its aluminium PM matrix after extrusion and drawing are reported. Preforms were manufactured by the cold pressing of RAl-1 aluminium powder and of its mixture with 10% SiC particles. They were extruded at 480ºC, with extrusion ratio = 4.2. No porosity was observed on longitudinal sections of the Al-SiC composite. The hardness and compressive mechanical properties of the materials were evaluated. The yield and compression strengths of the composite were higher than for the PM aluminium. After cold drawing with strain r = 0.09, the yield stress of the extruded aluminium increases from the range of 74 to 80 MPa to the range of 115 to 118 MPa and at a 0.75 strain flow, the stress increases to 160 MPa. The average yield stress of the extruded composite is 93 MPa and drawing increased it to 135 MPa; at a 0.75 strain flow stress, it increased from 150 to 180 MPa. For both the aluminium and the composite, the critical compressive strains are higher than 0.75.

The purpose of the study is to present low-energy and low-velocity impact issues of hybrid laminates based on aluminium alloys connected with glass/epoxy composite (GLARE type) composites and conventional glass fibre reinforced polymer (GFRP) used in aerospace. The tested laminates were prepared by means of the autoclave method. Their reaction to low- velocity impact was analyzed using a hemispherical impactor (diameter 38.1 mm). The laminates were characterized in terms of damage size and failure mechanisms after impact with different energy levels (1.5 and 2.5 J). After the impact tests, the failure was evaluated using ultrasonic, microtomography and microscopic methods in order to determine the nature of internal degradation of the structure. It was noted that low-energy impact phenomena are of importance in aerospace materials. They cause barely visible impact damage to composite materials. However, the used FML are innovative materials characterized by higher low-velocity impact resistance because of the superior properties of both metals and fibrous composite materials with a strong adhesion bonding. The damage of GLARE laminates is much less than in polymer composites. Some transverse cracks and micro-delamination between the composite layers and in the adhesive layer are the major failure types in GLARE laminates as a result of low-energy impact.

The paper presents the results of studies on a segment of acircular saw used for cutting concrete. Usually, such products are manufactured by powder metallurgy methods with an addition of diamond particles. This manufacturing technology of such materials is aimed at obtaining a ‘self-sharpening’ effect. The effects consist in matrix abrasion during operation and in exposing the cutting diamonds, then their falling out and the following matrix abrasion. In the process of manufacturing such materials, such a matrix composition should be chosen so as to ensure that the diamond particles feature good adhesion. Because of that, the studies were aimed at determining uniformity of the diamond particles arrangement in a fracture of the studied segment, and determining the element distributions in the material matrix. Chemical composition point analyses were performed using the EDS method as well as element distribution maps in the product matrix. An X-ray phase analysis was carried out to evaluate the possibility of forming intermetallic compounds between the matrix components which could have formed during sintering.

The concept of fabricating disc magnets for application in stepper motors has been presented. The disc magnets are composed of two elements, magnetized in the opposite direction, having a gradient structure. Such a structure produces a effect similar to the one in multi-pole magnetizing, which is difficult to implement, especially for small size magnets. The magnets were processed using Nd-Fe-B powder bonded by an epoxy resin. As a novelty in this concept, one can regard the application of centrifugal casting, directing the magnetic particles to the region of the active part of the magnet i.e. the part interacting with the magnetic core. In the applied solution, an elongated part having axial symmetry and a cross-section equal to that of the thus designed magnet. It was shown that by the application of resin of a carefully chosen viscosity, one can obtain various distributions of powder particles along the radius of the magnet. A more favorable structure of the composite magnet for this particular application was achieved using low viscosity resin, which enabled movement of the entire powder towards the active part and provided a 43% filling ratio. The studies showed that the flake-shaped powder used in the experiment, shows a tendency to form a morphological texture, i.e. the flakes tend to locate themselves perpendicular to the radius of the cast magnet. This method of fabricating disc magnets for stepper motors provides substantial savings, resulting from using a smaller proportion of Nd-Fe-B powder while maintaining a high filling ratio in the active part of the magnet.

Carbon nanotubes because of their high mechanical, optical or electrical properties, have found use as semiconducting materials constituting the reinforcing phase in composite materials. The paper presents the results of studies on the mechanical properties of polymer composites reinforced with carbon nanotubes (CNT). Before introduction to the polymer matrix, the nanotubes were subjected to chemical cleaning. Carbon nanotubes cleaning was carried out in the liquid phase using a mixture of oxidising concentrated nitric and sulphuric acids. Three-point bending tests were carried out on the composites. The density of each obtained composite was determined as well as the surface roughness and the conductance at room temperature. Carbon nanotubes constituting the reinforcement for a polymer composite improve the mechanical properties and conductivity of both the composite and the polymer.

The paper presents results of research on sintering, polycrystals manufacture and determination of the characteristics of the obtained NbC_1-x - NbO₂ composites. For the manufacturing of composites powders synthesized from the elements in the solid phase reaction method in the laboratory of Department of Ceramics and Refractories WIMiC, AGH were used. As a result of grinding and drying, carbide powders have undergone a surface oxide passivation. In order to improve the granulation and moulding capacity of powders and to partially deoxidize them, a small amounts of Nowolak MR resin were introduced into powders, as a carbon precursor. The prepared granulates were used to manufacture composites with the pressureless sintering and hot pressing. Mechanical properties, thermal and chemical properties were investigated and compared with the results obtained for the single-phase niobium carbide polycrystals. It was found that the composites are characterized by: high hardness (HV~16 GPa; HK 12÷14 GPa), higher than the polycrystals bending strength (~500 MPa) and fracture toughness (5 MPa∙m0.5) and good thermal conductivity (12÷15 W/m∙deg). Oxidation resistance of the composites is the same as the single-phase materials.

This paper investigates the structures of composite overwrapped pressure vessels (COPV) intended for use as storage tanks for compressed gas fuels in automobiles and other vehicles. The objective of this work was to establish the use of mosaic patterns arising during winding in the helical layers. In the authors' opinion, the optimal mosaic pattern considering the behavior of reinforcement tows under loading is the one designated as Nr1 in the matrix method. It exhibits the lowest number of crossovers, as well as their most orderly array - linear. Crossovers are considered as local distortion of a composite structure, which has a negative effect on the development of damage in the material. This statement is the result of previous studies performed by the authors, as well as papers by other researchers. In total, 9 different type 3 and type 4 vessels produced by filament winding were studied. The studies encompassed an analysis of the mosaic patterns in selected helical layers only. This work contains neither information on the thickness, sequence or winding angle in the helical layers, nor on the number of longitudinal or circumferential layers. The work presents non-standard methods for the assessment and designation of mosaic patterns. The mosaic patterns in the helical layers were designated in accordance to the matrix method. The patterns were compared to the Nr1 patterns, which are optimal because of the lowest number of crossovers. The results of the study point to a lack of good engineering practices in the usage of specific mosaic patterns in responsible high-pressure constructions. In the opinion of the authors, the only rationale for the use of specific mosaic patterns now in use by the industry is the visual effect and attractive, rhombic character of the pattern. Each vessel had a unique composite layer template . Among the analyzed vessels, only one Nr1 mosaic pattern was found. It was used in the layer laid down at the angle of 14°.

The paper presents the preliminary results of studies on obtaining copper-based composite materials strengthened with carbon nanotubes modified with copper nanoparticles. The nanotubes modification was carried out by chemically attaching copper nanoparticles originating from copper acetate. Electrolytically obtained copper powders were used as the matrix. The materials were consolidated by one-sided pressing followed by sintering. Microscopic examinations both of the powders and of the finished sinters were carried out using an Olympus GX41 optical microscope. Additionally, quantitative analysis of the sinters structure on non-etched microsections was performed. Computer software Image - Pro Plus was used to calculate the nanotubes surface fraction and their average surface area; the studied micro-particles aspect ratio was also determined. It has been shown that the nanotubes in the sinters, depending on the sintering method, differ in size and arrangement in the composite.

The applied methods for preparation of the reference powders contains high-energy milling in planetary mills, resulting in a particles size reduction to the dispersion level. Such a reinforcing particle size allows one to obtain high wear resistance. Apart from size-reduction of the ceramic phase, mechanical coupling of hard ceramic and plastic metallic (matrix of the composite) particles takes place. Stable coupling between the ceramic and metallic particles was obtained by pressing and sintering in a high-temperature press. This method allows one to eliminate the problems occurring in classic casting technologies applied for the manufacturing of composites such as: low wettability of the particles by liquid metal or a heterogeneously distributed reinforcing phase. In addition, the applied modification of the composite composition with glassy carbon particles, contributed to the change in the wear mechanism of the composite and cooperating cast iron. Evaluation of the tribological properties was performed by friction and wear coefficient determination. SEM observations of the composite powder and of the composite allowed the authors to evaluate the influence of the powder preparation process parameters on the composite microstructure.

Titanium implants are characterized by improved mechanical properties compared to human bones, that might lead to overtaking the whole load from the bone, which is conducive to bone resorption. One of the proposals to solve this problem is the use of composite materials based on a titanium matrix or titanium alloy matrix with an addition of hydroxyapatite (HAp) ceramics. The introduction of HAp to the metallic material contributes to improvement in biocompatibility and allows for integration of the implant with bone tissue. The focus of this study is on examining metallic-ceramic composites based on a titanium matrix or titanium alloy matrix with an addition of hydroxyapatite ceramics HAp (Ca₁₀(PO₄)₆(OH)₂) ranging from 20 to 40 wt.%, obtained by means of the spark plasma sintering method in the atmosphere of shield gas (argon), at the sintering temperature of 1000°C in SPS HP 5 equipment (manufactured by FCT). The samples were sintered for 25 minutes at the compaction pressure of 35 MPa. The composites were evaluated by means of structural analysis in microstructural examinations with an optical microscope, Neophot 32, and X-ray quality analysis using an X-ray diffractometer (Seifert 3003 T-T) and the following parameters: supply voltage –30 kV, current intensity –40 mA, measurement step 0.1º, integration time 10 s, characteristic radiation wavelength λCo = 1.790 nm. The hydrostatic weighing method in deionized water according to standard PN EN ISO 2738: 2001 was used to measure the density, porosity and water absorption. The surface profile of the biocomposites was determined using a Hommel T1000 roughness tester. The roughness parameters were measured in contact with the examined surface by coupling the stylus with a differential measurement system. The mechanical properties (hardness) of the metallic-ceramic composites based on a titanium matrix or titanium alloy matrix with an addition of hydroxyapatite ceramics HAp were evaluated. The aim of the study was to determine the usefulness of the SPS (Spark Plasma Sintering) method for manufacturing metallic-ceramic composites for medical applications.

Magnetorhelogical fluids (MRFs) are a class of multifunctional materials with the characteristics of reacting to a magnetic field by noticeable and reversible changes in their rheological and magnetic properties. The object of this study was MRFs with carbonyl iron particles based on a synthetic carrier oil. The effect of varying the mass of the solid state components such as carbonyl iron (CI) particles and fumed silica stabilizing agent additive on the performance of MRFs was examined. For this purpose, the microstructure of MRFs with different carbonyl iron addition was observed in the presence and of without a magnetic field. Moreover, the rheological properties characterization of different compositions of MRFs was conducted using a rheometer equipped with a magnetic field. It was found that the application of an appropriate proportion of solid components plays a crucial role in the formation of usable magnetorheological properties. The results of steady shear tests show that a higher mass proportion of carbonyl iron particles strongly affects the performance of MRFs, the yield stress as well as off- and on-state viscosity. A higher content of magnetic particles can ensure a substantial increase in the yield stress values of MRFs. The MRF containing 75% w/w CI achieved a yield stress at the level of 18 kPa in the magnetic field of 318 kA/m, while the MRF with lowest magnetic component mass concentration of 25% w/w reached only 0.4 kPa, whereas the MRFs with different fumed silica amounts achieved more comparable viscosity level and yield stress values. These results clearly indicate the decisive influence of carbonyl iron content on MRF performance. Oscillatory, rheometric measurements versus magnetic field show that the highest values of shear complex modulus were achieved by the MRFs with the highest percentage of carbonyl iron particles (75% w/w) and fumed silica additive (1% w/w). At the same time, the loss factor dependence on the fumed silica and carbonyl iron amount showed a much smaller effect on the MRF performance.

Composite materials have developed in recent years. Fiber reinforced polymer composites (laminates) and aluminum alloys currently constitute the most dominant materials applied in the aerospace industry. The paper presents the tensile properties of selected fiber metal laminates regarding the content of structural components. Additionally, the failure characteristics of the tested specimens were determined. The hybrid systems (Fiber Metal Laminates) in this study were based on the 2024-T3 aluminum alloy and glass and carbon fibers reinforced polymers. The tensile properties were determined according to ASTM D 3039. The strain gauge Vishay CEA-06-125UT-350 was employed to measure the strain. The results have shown that the tensile properties of both tested types of laminates depend on the metal volume fraction factor. The investigated specimens showed a bilinear character in the stress-strain curves. The findings imply that the tensile properties of fiber metal laminates depend on the type of composite reinforcement, metal volume contribution and fibers orientation. It can be noted that with a decrease in the metal volume fraction and a layer orientation change from 0 by 0/90 up to 45 results in a decrease in the Young's modulus of the tested laminates. Several fracture modes were identified depending on the lay-up configuration and type of reinforcing fibers. Use of the metal volume fraction approach in predicting the mechanical properties is appropriate for both carbon and glass fiber reinforced fiber metal laminates.

Model composites were made, for which the following components were selected: epoxy resin reinforced with layers of NCF (non-crimped fabric) with appropriately oriented glass, carbon and aramid fibres. The fabrics for the test were selected so as to allow the comparison of ballistic resistance depending on the type of material, thickness and sequence of fabric. Resin infusion technology was used in preparing the composites. The resistance of the composite models was tested for penetration with: 9x19 mm FMJ projectiles, at a bullet impact speed of ca. 360 m/s, fragment simulating projectiles (FSP) with a mass of 1.1 g and fragments of a model IED improvised explosive device containing fragments in the form of 3/16” bearing balls. Carbon composites have the highest resistance to perforation with a 1.1 g FSP fragment simulating projectiles of all the materials tested. The ballistic limit of a four-directional carbon composite with a surface density of 5.5 kg/m² is 305 m/s, and for a surface density of 21 kg/m² the ballistic limit is 780 m/s. The ballistic resistance of the carbon composite is related to its high shear strength - the highest of all the materials tested. In reference to the model of composite damage by the projectile, this means that the first stage of penetration, in which the material is compressed and subject to shearing force, is the determining factor in resistance to perforation.

This paper presents the results of studies on the electroless deposition of Ni-P/nano-TiO₂ composite coatings on pretreated polymeric substrates (PET polyester Mylar A type) and on carbon fibres (24k fibres with 7 µm Tenax rovings). The Ni-P layer was deposited from a solution consisting of NiSO₄ 0.1 M; NaH₂PO₂ 0.2 M; glycine 0.21 M, with a pH = 7.5÷8.5 and thiourea added as a stabilizer, as well as cetyltrimethylammonium bromide as a surfactant. Titanium(IV) oxide (Aldrich, grains 25 nm) in powder form was added, amounting to 10÷30 g/l, with ultrasonic homogenization of the suspension. Under the experimental conditions applied, partial sedimentation of the powder occurred. Deposition was performed at the temperature of 70°C, during 5÷15 minutes for the carbon fibers and 60 minutes for PET. The substrates were rotated at 1 rpm and the suspension was agitated with a stirrer. The composition of the deposited layers was determined by chemical methods and their surface morphology was investigated using SEM. Under the applied conditions, Ni-P/TiO₂ layers of a thickness within 0.3÷1 µm, titanium oxide content up to 17% by weight, and 2÷3% phosphorus by weight, were obtained.

Ceramic-polymer composites have great importance in many branches of industry. They are used, among the others in electronics, optoelectronics, plastics for the construction of nuclear reactors or spacecrafts. They also play an important role in the production of materials for the protection of the human body. These materials are formed of shear thickening fluids (STF), also referred to as dilatant fluids. They are non-Newtonian liquids, which are characterized by an increase in viscosity as a function of shear rate. Materials and devices based on shear thickening fluids dissipate an energy associated to shocks, impacts and vibrations very well. This paper presents the results of research on the effects of a molecular weight of dispersing agent on the rheological properties of shear thickening fluids. In the first step, liquids with poly(propylene glycol) of a molecular weight of 400, 425 or 725 g/mol (used as a dispersing agent) were prepared. As a ceramic powder, a nanosilica with an average particle size of 14 nm was used. Concentration of the powder was 12 vol.% or 15 vol.%. In the second step of this study, the rheological properties of the prepared fluids were analysed at 25 °C. The effects of the type of used glycol and the content of solid phase on the rheological properties were examined. More favorable results were obtained for the systems of 15% by volume of the solid phase. The influence of the temperature on therheological properties was also checked. Parallel measurements for systems with a poly(propylene glycol) of a molecular weight of 400, 425, 725 g/mol and a powder 12 vol.% at 37 °C were conducted. The effects of the viscosity leap were lower but were received at higher shear rates.

Increasing demands for energy efficient lightweight structures capable of working in complex termomechanical loading conditions require the selection of appropriate load adapted materials as well as the development of associated manufacture processes ready for series production. Metal matrix composites with their advantages such as high thermal stability, reinforcement structure designability and high specific material properties have become more popular among materials applied as reliable load bearing products. To adapt the manufacturing process for these composites, understanding of solidification processes, the type and formation of interface and thermal behaviour of the composite are indispensable. The aim of this work was to understand the thermal behaviour of aluminium based metal matrix composites reinforced with carbon fibres 3D textile manufactured via the high pressure die casting (HPDC) process. Within the residual stress analysis and the sensitivity analysis of fibre coatings, plane specimens made of Al-226D with a carbon fibre (HTS) reinforcement with a nickel phosphorus coating have been investigated. Differential scanning calorimetry (DSC) and dilatometry tests have been performed considering the anisotropy of textiles and the formation of a crystallisation front in the cast specimens.

Laminated Ti-(Al₃Ti+Al) and Ti-Al₃Ti composites have been synthesised with controlled temperature and treating time using 50, 100 and 150 µ m thick titanium and 50 µ m thick aluminium foils. Microstructural examinations showed that Al₃Ti was the only phase formed during the reaction between Ti and Al. After 20 minutes of treating at 650 ° C, not all the aluminium was consumed and the composites consisted of alternating layers of Ti, Al and Al₃Ti. After 60 minutes, the aluminium layers were completely consumed, resulting in microstructures with Ti residual layers alternating with the Al₃Ti layers. Tensile strength, flexural strength and impact toughness measurements were performed on the materials with different microstructures to establish the properties and fracture behaviour. After 60 minutes of treating, all the composites had a higher yield strength, higher ultimate tensile strength and higher flexural strength than those composites after 20 minutes of treating produced with the same thickness of starting Ti foil. On the other hand, the strain at fracture and impact toughness of the composites behaved conversely. The results of the investigations indicated that the mechanical properties of the composites strongly depend on the thickness of the individual Ti layers and the presence of residual Al layers at the intermetallic centrelines.

A significant role in metallurgical and foundry processes, inclusive of the ones related to composite material technology, is played by interfacial tension arising in technological systems. In the systems related to the technology of composite castings (both ones reinforced with particles and with saturated reinforcement), interfacial tension, particularly during recycling processes, appears at the boundaries of three phases: liquid metal (alloy), liquid slag, and atmosphere, in any combinations. Knowledge of the values of these parameters facilitates the designing of technological processes. Therefore, a useful measurement method of these tensions should allow for the measurements to be carried out during a single experiment. The authors have tested a chosen method, being a combination of plate and ring methods, and found its usefulness in the case of systems composed of liquid aluminum alloys and melted salt mixtures. Since the method is based on the measurement and recording of the forces acting at the probe (solid phase) moving successively through a layer of liquid metal (alloy) to the layer of liquid slag and, afterwards, to the atmosphere, proper interpretation of the plots of the changes in the forces recorded by the measurement system have become very important. Observation of the measurement process in real systems is very difficult (or even impossible). Hence, the authors have carried out tests with the use of equivalent media at room temperature, and obtained model plots of the recorded changes in the force values in conditions of fully clear behaviour of the examined systems. Thanks to these experiments and the observations, the authors have attained necessary and unquestionable information for full interpretation of plots illustrating the changes of recorded forces under the conditions of tests using metallurgical systems occurring in the technology of e.g. recycling of cast composite materials in the matrix of aluminum alloys.

Tin(IV) oxide - carbon nanotube nanocomposites were synthesized by the sol-gel method without and with ultrasonication, microwave radiation, and cavitation. The synthesized products were examined by means of transmission electron microscopy (TEM), X-ray diffraction, and differential thermal analysis methods. The TEM micrographs have shown that the tin (IV) oxide was deposited onto the oxidized surface of MWCNTs. The X-ray diffraction patterns have shown that the crystallite size of the SnO2 was within the 6.7÷11 nm range. The thermal analysis data indicate that the thermal stability of the SnO₂ - MWCNТs composites increases versus the initial carbon nanotubes. The scheme of transformations in the tin(IV) oxide - carbon nanotube nanocomposite synthesis by the sol-gel method was proposed.

Recently, the shear thickening phenomenon has drawn the attention of many researchers. The ability of shear thickening fluid to resist operative force creates a possibility of applying this kind of material wherever there is a necessity to dampen and disperse energy. Therefore, dilatant slurries have found their application in dampers, devices that protect buildings against seismic shocks or military applications in so called “liquid armor”. A great deal of research has focused on investigation of the mechanism and influence of parameters such as volume fraction, polydispersity and medium viscosity of the dilatant effect, however, some fields are still unexplored. In this work, the influence of nanosilica particle size on the dilatant effect of shear thickening fluids was investigated. For the tests, nanosilica with diameters of 7 and 200 nm was chosen. The suspension was prepared by dispersing the nanosilica into poly (propylene glycol) of a molecular weight of 400 g/mol. The concentration of the ceramic powder varied from 12 to 30 vol.%. The influence of the particle size on the dilatant effect was observed by a rotational rheometer Kinexus Pro with a plate-plate system. In this case, viscosity as a function of shear rate was measured. The shear rate increased from 1 to 1000 s^-1. The measurement showed that the diameter of silica particles has a significant influence on the rheological properties of the investigated suspensions. With an increase in particle size the dilatant effect increases. However, its position is shifted to a lower shear rate. The maximum volume fraction and relative viscosity of the suspension also was examined. The measurements showed that with increasing particle size, the relative viscosity of the suspension decreases, which result in an increase in the maximum volume fraction of nano-SiO₂.

The study presents the results of experimental testing of a layered cross-ply [0/90]_n E-glass/polyester composite in the range of the selected compression properties at high strain rates = 2300÷4600 s^-1 and a quasi-static strain rate = 0.0067 s^-1. The composite was manufactured using contact technology using Owens Corning CD-600 E-glass stitched fabric and Polimal 104 polyester resin. The circular cross-section specimens of three sizes 2.5, 5 and 7.5 mm in height and 15 mm in diameter were tested in the above described experiments. To determine the static properties, quasi-static experimental tests were conducted using an Instron 8802 machine in the displacement control mode at a constant crosshead speed of 1, 2 and 3 mm/min respectively for the 2.5, 5.0 and 7.5 mm specimen types. The compression loading was monitored with a load cell Instron ±250 kN, whereas the axial strain with an Instron 2620-604 extensometer using additional fixing discs. The measuring base of the extensometer was equal to the specimen height. Identification included the stress-strain curve, strength, Young’s modulus and failure strain. For the high strain rates testing, a modified Split Hopkinson Pressure Bar test system was used, containing an LTT 500 Amplifier made by Tasler, Germany and an NI USB-6366 data acquisition device made by National Instruments, USA. The failure modes observed under high strain rate loading were similar to those observed under quasi static loading. The samples predominantly failed by shear fracture. Reduction of the specimen height implies an increase in the nonlinear effects in the initial part of the stress-strain diagrams (increasing strain at same stress), probably caused by the boundary effect. The main parts of the stress-strain plots are approximately linear, thus the linear elastic-brittle material model can be assumed. It was generally observed that the compressive strength and Young’s modulus along the thickness direction are higher at high strain rate loading compared to the results at quasi-static loading.

The influence of impact damage on the dynamic behaviour of dry and wet thermoplastic fibre reinforced samples has been investigated. The change of the structural state could be detected in the changes of the modal parameters. In the first part of the investigations, appropriate modes were selected for a reliable structural state detection of the samples. The accuracy of determining these parameters could be identified for the chosen measurement method. Within the second part of the work, the changes in the modal parameters caused by moisture, impact damage and the combination of both have been investigated. This research serves as a foundation for modal analysis based a structural health monitoring (SHM) system for composite structures that include the effects of moisture.

The new trend in designing and manufacturing machines and devices e.g. for the food and pharmaceutical as well as automotive industry, is replacing lubricating oils with solid lubricants incorporated into the surface layer of engineering materials. Incorporating solid lubricants helps decrease both the friction resistance and wear of rubbing parts as well as reduce the amount of lubricating oils to ensure efficiency and effectiveness at much lower operational costs. Moreover, the use of a solid lubricant as an additional phase in a friction material does not damage the environment by oil penetration through leaks or accumulation of waste oil residues. At the Silesian University of Technology, a novel method of obtaining a new generation composite containing glassy carbon as a solid lubricant has been developed. The uniqueness of the elaborated technology is the fact that glassy carbon is produced directly in a ceramic from a previously introduced liquid precursor. Such a solution, compared to the so far applied methods where the prepared carbon particles are mixed with the alloy matrix, appear to offer some advantages. Firstly, the manufacturing costs are lower because there is no need for the expensive procedure of mixing the reinforcing phase with the liquid metal matrix. Secondly, glassy carbon distribution throughout the entire volume of the composite is uniform, free from sedimentation or agglomeration and particles clustering. The presence of uniformly distributed glassy carbon greatly affects the tribological properties of the composite. This is possible due to the low shear resistance and high hardness as well as excessive thermal stability of the glassy carbon. An additional advantage seems to be its low thermal expansion. The friction coefficient determined during rubbing against cast iron GJL-300 in the conditions of friction in air ranges between 0.08 to 0.14.

Aluminium alloy based composites were prepared by hot pressing in a vacuum in order to study the strengthening effect of an amorphous phase addition in the form of ball milled powder from melt spun ribbons of the Al₇₃Si₅Ni₇Cu₈Zr₇ (at.%) alloy. For comparison, a composite with a strengthening ceramic Al₂O₃ phase was hot pressed under the same conditions. DSC measurements allowed the authors to determine the start of the crystallization process of the amorphous ribbons at 240°C. The presence of the majority of the amorphous phase in the melt spun ribbons was additionally confirmed by the X-ray diffraction technique which also revealed the presence of an α-Al solid solution and some peaks of intermetallic phases. SEM studies showed homogenous distribution of the strengthening particles in both kinds of composites and confirmed the existence of α-Al and some intermetallic crystallites inside the metallic amorphous particles. The hardness of all the prepared composites was comparable and amounted to approximately 50 HV1 for those with the Al matrix and 120 HV1 for the ones with the 2618A alloy matrix. The composites have shown a higher yield stress than the hot pressed aluminium or 2618A alloy. SEM studies of the cracks after compression tests revealed that the interfaces between the strengthening phase and matrix in metallic amorphous powder-Al /2618A alloy composites show a different character of the interface between the ceramic particles and the Al matrix. Therefore in the composite with the Al₂O₃ particles, cracks have the tendency to propagate at the interfaces with the matrix more often than in amorphous/Al composites.

The results of examinations of polyoxymethylene (Tarnoform) with quartz sand composites are presented. Investigations were made for composites with quartz sand covered with a 20% type A 1100 aminosilane water solution. A composite with a 30% filler content was made using an extrusion machine collaborating with a granulator. Composites of lower filler contents (10 and 20%) were made by the addition of a proper amount of Tarnoform to the 30% composite. The samples for the examinations were made using a KraussMaffei KM65-160C1 screw injection moulding machine. Investigations were conducted on the samples before as well as after UV ageing. Investigation of the mechanical properties: tensile strength and hardness were made, and also the thermal properties, gloss and color were determined. The aim of the investigations is to determine the influence of the filler and UV ageing on the composite properties and to receive a new, cheaper constructional material. The lowest value of melting enthalpy of the POM/ quartz sand composite was obtained from samples after UV ageing. An increase in the lightness value after the ageing process of POM filled with quartz sand was obtained. The character of the changes of the a* and b* coordinate values for the examined materials before and after the ageing process was evaluated, which proves the essential influence of the filler addition on the colour change. The tensile strength of the composite decreases, while the hardness increases as the content of quartz sand increases both before and after the ageing process.

The chemical reduction method, as one of the processes very often applied in surface engineering, allows one to obtain materials with good performance properties. Electroless Ni-P layers have been extensively applied in industry, microelectronics and materials engineering due to their unique and exceptional properties. Thanks to the addition of carbon nanotubes as a dispersion phase, it is possible to obtain layers with improved properties. Solid particles in a nickel matrix have been developed to achieve better wear resistance, corrosion resistance, microhardness and tribological properties. The study is concerned with composite layers consisting of a nickel-phosphorus (Ni-P) matrix and a dispersed carbon nanotube (CNTs) phase. The Ni-P layers and composite layers were deposited on a S235JR carbon steel substrate by the chemical reduction method. The process of manufacturing both layers was carried out by means of sediment electroless depositions in a nickel sulfate bath. The paper describes the technique of manufacturing Ni-P/CNT layers, the methods of CNT identification in the Ni-P layer, and presents the results of examinations of the mechanical properties (micro-hardness examinations) of the layers of the final products. The CNTs introduced into the Ni-P matrix improve the properties of the Ni-P layers and thereby the useful properties of the products covered by Ni-P/CNT coatings.

The article presents the analysis of failure for a reinforced concrete beam with a low level of reinforcement, made of high strength concrete, in the process of static deformation in comparison to experimental results. On the basis of its ultimate uniaxial compressive strength, the methodology for defining the parameters of the constitutive model for high strength concrete was developed. The comparison of the obtained results indicates the correctness of the assumptions and constitutive models of the high strength concrete and reinforcement steel, and also the effectiveness of Crisfield’s arc length method and the Newton- Raphson iterative solution with adaptive descent. The numerical results of the smeared crack patterns proved to be qualitatively agreeable, regarding the localisation, direction and concentration, with the experimental results.

An attempt was made to modify water glass with a propanol suspension of magnesium nano-oxide obtained by the thermal method. Foundry binders are usually complex synthetic materials of different chemical nature. Due to their specific chemical composition, they often pose a threat to both humans and the environment. Therefore, the constantly tightening rules on environmental protection have compelled the foundry industry to replace hazardous organic binders with less harmful ones, i.e. inorganic. Considering the above requirements, a foundry binder with a promising future seems to be water glass. It is cheap, easily accessible, and non-toxic. At the same time, the potentials of water glass as a binder for moulding and core sands have not been so far fully explored. The effect of the modifier and its content on the R_m^U tensile strength of loose moulding sands was examined. The content of modifier was determined at which the sand reaches the highest and the lowest values of R_m^U. This content amounts to 3 mass% and 5 mass% giving 1.61 MPa and 0.42 MPa, respectively. It was proved that the maximum value of R_m^U was the effect of the chemical reaction of water glass with magnesium nano-oxide, while the minimum value of R_m^U was due to the excessive binder wettability of the sand grains, hindering the formation of strong binding bridges in the sand mixture. FT-IR studies revealed the presence of chemical reactions taking place between the binder and modifier, the result of which was the presence of Mg²⁺ cations in the of water glass structure.

The paper concerns composite materials based on a thermoplastic polymer and low melting metal alloy. Composites with various alloy content were prepared by the sintering of PMMA or PVC powder to obtain a matrix with open pores. Then, liquid Wood’s alloy was intruded into the matrix using a pressure autoclave. The obtained systems consist of co-continuous, interlaced 3D networks. The microstructure, electrical and thermal properties have been investigated. SEM micrographs revealed good dispersion of the filler in the matrices. The metal alloy inclusions have irregular shapes and different sizes from a few µm up to 100 µm. The results of the resistivity measurements showed that both composites conduct electrical current well. The resistivity of the samples varies from 4.2•10^-4to 1.5•10^-5 Ω•m and the type of matrix does not have an influence. In contrast to electrical conductivity, the concentration dependence of thermal conductivity did not show percolation beha¬viour. The thermal conductivity of the composites increased but only slightly and its value is still closer to the polymers than to the metals. A slight reduction in the Vicat softening point of the composites was observed. It is due to the low melting temperature of the alloy, i.e. 70°C.

The article presents the analysis of the stress and strain state of reinforced high strength concrete beams with a low level of reinforcement in the process of static deformation in comparison to experimental data, according to the methodology of determining the parameters for the constitutive model of high strength concrete, based on its ultimate uniaxial compressive strength. Three variants of numerical solutions of the BP-1a beam were presented, which are distinguished by their failure surface. Numerical calculations made with the use of the Newton-Raphson method with adaptive descent and Crisfield’s arc length method are verified with experimental results. The development of strain for extreme concrete fibres of the compression zone and the development of strain for a longitudinal reinforcement bar in the tension zone at beam’s midspan are characterized by excellent agreement in the presented cases.

The article presents the analysis of the load capacity and deflection of a reinforced high strength concrete beam with a low level of reinforcement in the process of static deformation in comparison to experimental data, according to the methodology of determining the parameters for the constitutive model of high strength concrete, based on its ultimate uniaxial compressive strength. Three variants of numerical solutions of the BP-1a beam were presented, which are distinguished by their failure surface. Numerical calculations made with use of the Newton-Raphson method with adaptive descent and the arc length method are verified with test results. The load-deflection relationships for the flexure beam from the experimental data and the finite element analyses are in good agreement up to failure. In all the cases, the differences between the final loads for the model and the ultimate loads for the experimental results are less than 5%.

In the paper, a research study is presented that was carried out for the purpose of obtaining composite materials based on a commercial micron boron carbide. A hot pressing process was performed to produce all the necessary materials. Chromium carbides, chromium silicides, and chromium boride were used as sintering activators, and as the phases generating thermal stresses (to improve fracture toughness). Some additives were introduced, their amounts not exceeding 5% of the total volume of the sample. In the case where large amounts of the introduced phases were applied, the sintering temperature was reduced by 120°C as regards the boron carbide sintered with carbon. The phase composition and the structure of the sinters produced were analyzed. The microstructure of polished and chemically etched (in molten salts) samples was investigated using scanning electron microscopy. The elastic properties, hardness, bending strength, and fracture toughness of the products were also determined.

The study examines a shell segment made of glass-polyester layered composites with fabric- or mat-reinforced layers. The segment is a single-wave, single-shell, and simply supported one, with a span, whose initial geometry and ply sequences were patterned after the cover segments of a selected rectangular tank in a sewage treatment plant in Germany. The aim of the study is multi-criteria quasi-optimization of the cross-section shape of the shell of the segment with flat flanges, with fixed, overall dimensions and ply sequences. The segment is subjected to a static three-point bending test with kinematic excitation. The optimization criteria are as follows: maximum load capacity of the segment, minimum weight of the segment, technological feasibility, and architectural effect. Numerical models of the segments with specified geometry of the cross-section (6 objects in total) were built using the Altair HyperMesh 11.0 system (finite element mesh) and MSC.Marc / Mentat 2010 (analysis set). The geometries were earlier prepared in the Generative Shape Design Catia v5r19 module. The numerical calculations (simulations) were performed using the MSC.Marc 2010 solver for non-linear analyses. The methodology for modelling and simulation of the composite shells, developed in the authors’ previous papers, has been applied.

According to Takagi's definition, an intelligent material is able to react to external stimulus by a significant change in its properties in order to make a proper and successful response to the stimulus. The rheological behaviour of magnetorheological composites (MRC) can be controlled continuously, rapidly and reversibly by an applied magnetic field. In this paper, an acrylic copolymer with carbonyl iron powder (CIP) is tested in conditions of mechanical and magnetic stimulations. Chitosan-coated magnetic particles are made in order to change the hydrophilic surface character of CIP to hydrophobic and as a result, obtain better compatibility between the particles and the matrix. The test samples are subjected to cyclic shearing with a constant frequency of 1 Hz. The change in the magnetomechanical properties is expressed by the relative change in hysteresis loop area δW and stress amplitude δτ. An increasing content of carbonyl iron in the composites and the strength of magnetic field H causes an increase in the hysteresis loops area. Material containing modified particles has a significantly bigger hysteresis loop area than samples filled with unmodified carbonyl iron powder. Based on this knowledge, it can be concluded that this sample can dissipate much more mechanical energy.

Higher performance and reliability, reduced fuel and lubricant consumption as well as a greater solicitude to the earth's environment are nowadays the main driving forces of progress in contemporary automotive, aviation and spacecraft industries. Among the effective solutions of these issues are friction reduction in the powertrains of vehicles as well as mass reduction of engines by means of the replacement of steel parts of engines or other mechanisms by twice lighter ones made from titanium alloys. In the paper, basic information concerning the manufacturing of two types of thick carbon or MoS2-based friction reducing nanocomposite coatings is given and part of the characterization results concerning their microstructure, mechanical and tribological properties as well as the corrosion resistance of nanocomposite nc-WC/a-C and MoS₂(Ti,W) coatings deposited by magnetron sputtering onto Vanadis 23 HS steel and hardened Ti6Al4V titanium alloy substrates are presented and discussed. The work was accomplished by an interdisciplinary team of researchers from AGH University of Science and Technology in Krakow, the Motor Transport Institute in Warsaw and of the Lodz University of Technology in the frame of the POIG project KomCerMet (Workpackage KCM3) financed by the Ministry of Science and Higher Education of Poland. Keywords: nanocomposites, coatings, nc-WC/a-C, MoS₂, nanostructure, dry friction, resistance to corrosion & wear, protection against galling

Ferroelectric-ferromagnetic composites based on ferroelectromagnetic PbFe_1/2Nb_1/2O₃ powder and ferrite powder (zinc- nickel ferrite-NiZnFe and zinc-manganese ferrite-MnZnFe) were obtained in the presented study. The volume fraction of ferroelectromagnetic powder in the composite PFN-MnZnFe was equal to 90%, while the ferrite powder fraction was 10%. Synthesis of the components of the ferroelectric-ferromagnetic composite was done by the powder calcination method. Final densification was done by the pressureless sintering method. On the obtained ferroelectric-ferromagnetic composites, XRD investigations were performed as well as investigations of the microstructure, EDS, dielectric, magnetic, internal friction and electrical hysteresis loop. The results of these investigations have shown that the combination of ferroelectromagnetic PFN with magnetic ferrite caused an increase in the value of the dielectric permittivity of the composite. Therefore, the addition of the ferrite (Ni_1-xZn_xFe₂O₄, Mn_1-xZn_xFe₂O₄) as an additional component improves the magnetic properties of the PFN-ferrite composite. Taking into account the fact that the electric conductivity of zinc-manganese ferrite (MnZnFe) is higher than the zinc-nickel ferrite (NiZnFe), it seems to be a better material for obtaining composites based on ferrite and PFN powders.

The methods of manufacturing composites with spatial variation in the reinforcement distribution which exploit reinforcement segregation in the liquid matrix are among the most effective ones. However, methods based on density differences such as gravitational casting and centrifugal casting have their limitations in the range of reinforcement configurations that are possible to obtain. An alternative is to exploit the phenomenon of electromagnetic buoyancy occurring in situations where the particles and the matrix have different electric conductivities. This paper presents some possibilities of exploiting this phenomenon to obtain the local reinforcement of a bush made of aluminum alloy AK12 with SiC particles at its inner wall. The paper discusses the model of such a process and the effect of its parameters on the trajectories of the particles moving in the molten matrix.

In water there are several pollutants having a significant impact on human health. The greatest difficulties are associated with the removal of viruses due to their small size (generally in the range of 20 to 400 nm). Currently, the most effective ways of removing of viruses from water are filters based on electrostatic adsorption. In this method, negatively charged viruses (in the pH of drinking water, pH 5÷9) are retained on an oppositely charged filter surface. These filters are characterized by large pores allowing a much more efficient flow of liquid through the filters and also eliminating the blockage of pores. In order to provide ceramic filters with a positive charge, their inner surface is modified. The purpose of this study was to obtain ceramic composite materials on the basis of zinc oxide with active layers from zinc oxide and simulate the filtration process using a polymer dispersion characterized by a similar size of particles to that of viruses and a negative charge in the pH of drinking water, as is in the case of viruses, was carried out. In order to obtain ceramic composite materials, two types of zinc oxide were used. The average grain sizes of the powders were different - an average particle size of about 200 nm for the powders which were purchased from NanoTek and about 7 μm for those which were purchased from POCH. Porous ceramic composite materials were formed by unilateral pressing. A 10 wt.% aqueous solution of poly(vinyl alcohol) with a molecular weight of 67 000 and degree of hydrolysis of 88% was used as the binder in the ceramic materials. Zinc acetate ((CH3COO)2Zn) was used to obtain the active layer of the ceramic composite materials while 0.01 wt.% solutions of polymer dispersion with a negative electrokinetic potential - Rokryl SW 4025 (Rokita S.A.) - was used to simulate the process of filtration. During the study, measurements characterizing the ceramic powders, measurements of the physical and mechanical properties of the samples were performed. The influence of the pressure (10 and 30 MPa) and additive of nano-ZnO (0 to 10 vol.%) on the tensile strength, open porosity and distribution of the pore size in the samples after sintering at 900 ºC were determined. Moreover, the effectiveness of the filtration process using the porous ceramic materials with an active layer of ZnO, which was formed by the impregnation of ceramic samples by zinc acetate and sintered at 430 ºC, were evaluated.

The research presented here was devoted to the pressureless sintering of composites consisting of a SiC matrix and intentionally introduced particles of solid lubricants as a dispersed phase. The goal of using such materials is to achieve a selflubrication effect in friction seal elements during sliding contact. In the first part of the investigations, the optimal conditions of sintering, as well as the best composition and concentration of the solid lubricants were established. The second part of the work consisted in characterizing such mechanical and tribological properties of the materials as: hardness (HV and HK), bending strength, abrasive wear resistance, friction coefficient and linear wear in contact parts made of homonymous and heteronymous materials. Based on the tribological and mechanical studies correlated with microstructure investigations (SEM), the material fulfilling the requirements for the construction of self-lubricating seal elements was selected.

The number of critical bone defects caused by injury, cancer or aging of the world population is increasing. Techniques currently used to repair these defects suffer from several disadvantages, such as a lack of mechanical and biological matching of bone characteristics, the requirement of second surgery and the risk of pathogen transmission. Scaffolds made of bioresorbable polymers are a promising alternative as they temporarily support regeneration of the damaged site and undergo complete degradation after new tissue is formed. The goal of the present study was to determine the changes of the mechanical properties of fibrous PCL-based nanocomposite scaffolds during in vitro degradation. The composite scaffolds containing PCL, 5 wt.% of hydroxyapatite nanoparticles, HA, and different concentrations of PLGA were prepared by combined sol vent casting and solid freeform fabrication techniques. The composite scaffolds were subsequently put to a dynamic degradation test. After fixed periods of time, the mechanical properties, mass loss of the scaffolds and change of the surface morphology (SEM) were determined. It was observed that the addition of PLGA accelerated the degradation of the scaffolds. However, the mechanical properties increased during the first weeks of incubation.

Polyoxymethylene nanocomposites with octakis (dimethylsiloxy, ethyl epoxycyclohexy) octasilsesquioxanes (POSS) were obtained during melt blending. The influence of the POSS nanoparticles on the morphology and mechanical properties of polyoxymethylene (POM) nanocomposites properties was investigated. POM/POSS nanocomposites were produced by means of melt mixing of POM with POSS; with a POSS content of 0.5, and 1 wt.%. The uniaxial elongation test of polyoxymethylene has been performed to determine the influence of POSS on the mechanical properties of the new hybrid material. The dispersion of POSS in the POM nanocomposites was studied by scanning electron microscopy (SEM). According to the mechanical investigation, it was found that the process of polyhedral oligomeric silsesquioxane (POSS) addition leads to an enhancement of both the tensile strength and stiffness, where the most encouraging results were achieved for the POM/POSS nanocomposites with 0.5 wt.% POSS. The SEM studies allowed us to provide direct evidence of better interfacial adhesion between the POSS particles and POM matrix, which may lead to better mechanical properties, specially tensile strength, elongation and stiffness. The obtained polymer composites POM/POSS are an interesting group of materials of construction, showing very good performance.

One of the basic requirements needed for proper aircraft operation in combat situations is the provision of an adequate number of airfields and a sufficient level of operational readiness. The rapid repair of airfield pavements enables quick resumption of air operations. The existing technology and methods of airfield pavement reconstruction could not meet the stringent time requirements of military operations, that is why mobile, composite airfield mats have been developed. In the paper, the operational and maintenance advantages of the elastic, mobile airfield mat ELP-1 KRATER manufactured by Stocznia Żuławy Sp. z o.o. are shown. The results of field and laboratory tests, performed by the Air Force Institute of Technology, Poland (ITWL) are also shown. The laboratory tests consisted of basic material property testing, as well as fatigue testing of the composite material. Strength tests of the mat-to-ground anchoring bolts were also performed, the results of which are presented in the paper. The field tests consisted of two stages: static and dynamic. In the static tests, the quality of the crater soil filling was tested with pressure plates and deflectometers. The dynamic testing had the form of several runs with a heavy truck on the mat-subbase system instrumented with strain gauges. These braking runs were an approximation of the loading conditions present during aircraft landing, and the weight of the test vehicle was comparable to the weight of transport aircraft. The overall levels of the recorded reaction forces were low, and the heaviest loading occurred during the most aggressive braking and turning maneuvers. The preliminary numerical model of the system consisting of the mat and the soil subbase is also presented. The numerical analysis was performed with the use of the Finite Element Method (FEM). A local model used to test the subbase stiffness was created alongside an associated global model which was employed to simulate the heavy test vehicle runs. The FE analysis has confirmed the theoretical assumptions and helped to put the experimental results in a proper framework. The overall evaluation proves that the mechanical strength of the composite mats is sufficient to withstand loads that may come from heavy military aircraft.

Titanium diboride has many advantages such as a high melting point, high Young’s modulus, low density, good thermal conductivity and high Vickers hardness. Therefore, the addition of TiB₂ to metal matrices has also been observed to greatly increase stiffness, hardness and wear resistance. The aim of the studies was to determine the influence of different contents of TiB₂ ceramics on selected properties of AISI 316L austenitic stainless steel. Metal matrix composites containing TiB₂ as a particulate phase were produced by high pressure-high temperature (HP-HT) sintering. Next, the apparent density (ρ_o) was measured using the hydrostatic method. The hardness was determined by the Vickers method. Young’s modulus measurements of the sintered composites were also taken using the ultrasonic method of measuring the transition speed of transverse and longitudinal waves. This paper also presents the microstructure analysis of composites with different contents of TiB2 particles. The composite was analyzed by observations with an optical microscope, scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). It was shown that the properties of the composites significantly depend on the sintering conditions. Generally, the application of a larger participation of strengthening phase improves the properties of the sintered composite materials. The microstructure of the composites with different contents of TiB₂ consisted of a fine and uniform TiB₂ particle distribution along the grain boundaries.

The work describes the microstructural changes occurring during the ceramization of silicone rubber-based composite in different conditions. Ceramization is a phenomenon which assures the compactness of polymer-based composites in the case of its thermal degradation caused by open fire or exposure to high temperatures. Polymer-based materials used as wire coatings contain a certain amount of mineral additives. Their type, volume, and grain size distribution are decisive for shaping the microstructure of a ceramized body. Moreover, the ceramization conditions can strongly influence its final microstructure. The total porosity, open porosity, pore size distribution and ceramized body compactness evolve with changes to the degradation temperature of the composites at which they have been studied.

The phenomenon of silicone rubber ceramization is based on preventing the release of volatile compounds resulting from the thermal decomposition of the polymer matrix through the creation of a ceramic coating on the composite surface. Usually, the coating is composed of mineral filler particles, combined with a fluxing agent. The ceramic barrier created is to protect the copper wire inside the cable from melting, which is additionally strong enough to maintain the mechanical integrity of the electrical circuit. The paper presents experimental data on the mechanical properties of silicone rubber composites, the morphology and strength of their ceramized layer and associated thermal characteristics and flammability of the materials. The results were analysed in terms of their material composition, type, size and surface modification of the mineral fillers. The composite with wollastonite exhibited the most stable structure and properties. Their porosity was the east dependent on the thermal conditions of ceramization, leaving a considerable amount of sub-micron pores up to the highest temperatures.

Carbon nanotubes are one of the strongest materials of unique mechanical, optical, electrical and electronic properties. Because of that they are mainly used as semiconductor materials constituting the reinforcing phase in composite materials. Most frequently nanotubes are obtained using the following methods: catalytic pyrolysis (CVD), electric arc method or by catalytic laser synthesis. The paper presents the results of studies on the topography of multiwall carbon nanotubes (MWCNTs) obtained by the CVD method, using an atomic forces microscope (AFM). Prior to the studies the nanotubes were cleaned using two methods - one part was cleaned in a mixture of concentrated sulphur and nitric acids, and the other in a mixture of perhydrol and acetic acid. Measurements of the surface topography using the Tapping Mode method were performer on the material prepared in this way, acquiring the data on the height and on the phase imaging.

This paper presents the results of laboratory research on concrete beams with alternative types of reinforcement, assuming a constant volume of fibers. As the reinforcement of the cement matrix, two types of macro-fibres, namely steel and polypropylene fibres, were used. In addition, traditional beam reinforcement in the form of aligned, smooth, and ribbed steel rods were tested. In the case of the long fibers-the steel bars were assumed to force the long fibers to adopt a certain position – four rods at the corners of the cross section, two of which were in the tension zone and two in the compression zone. By introducing a slip sleeve in three stirrups to stabilize the transverse bars in the desired position, efforts were made to ensure the independent operation of each of the four rods. It was shown that the highest load-carrying capacity and the toughness of the composite, was obtained for concrete beams reinforced with ribbed steel rods. Unexpectedly, the beams with the polypropylene fi bers and smooth steel rods showed substantial susceptibility to deflection. In both cases good interaction between the reinforcement and cement matrix was observed. The fracture toughness of the reinforced concrete and steel synthetic macrofibres in the share volume was comparable to 1.65% as documented by an equivalent flexural strength.

The advantages of FML structures (e.g. GLARE or CARAL) come from the improvement in durability of such structures, however, in such structures failure modes may also occur. Failure modes which may occur in such structures are similar to those in epoxy composites but some of them are associated with fracture mechanics similar to e.g. aluminium alloys. The quality control of materials and structures in aircraft is an important issue, also for FML laminates. For FML parts, a 100% non-destructive inspection for internal quality during the manufacturing process is required. In the case of FML composites, the most significant defects that should be detected by non-destructive testing are porosity, delaminations and cracks. In this paper, the use of non-destructive different methods for the inspection of Fibre Metal Laminates was presented. The novelty in the approach will include the use of multimode and highly specialized inspection methods such as: ultrasonics, thermography, air-coupled ultrasonics, and X-ray tomography.

The inner material structure as well as voids and damages in composite materials have a significant influence on mechanical material behaviour. Thus, for a reliable application of composites in safety relevant lightweight structures, knowledge of the inner material structure is of utmost significance. Computer tomography is an especially important part of nondestructive testing (NDT) both in research and industrial applications for non-transparent composites. Besides that, a novel in situ CT which enables the preparation of tomograms of specimens under loading conditions offers a better understanding of damage processes in composites. The paper gives examples for the advanced analysis of fibre-reinforced composites and their degradation behaviour using novel CT systems. The advantages of high resolution CT scans as well as corresponding FEM results are shown and an overview of the numerous application possibilities is given.

The scope of the study is to evaluate the behaviour of exemplary glass fibre preforms during the vacuum infusion process. The reinforcing preforms were prepared from: plain weave crimp fabric, chopped strand mat (with two alternative binders - polyester-appropriate and universal), a unidirectional (UD) fabric and a 3 mm PARABEAMR® 3D rising fabric. ESTROMAL 14 polyester resin was used as the matrix. All the laminates showed a fibre volume fraction in the range of 49÷52%. The permeability analysis was conducted with the use of PAM-RTM software by the ESI GROUP. As the base for the analysis, measured experimental saturation times were used. It is probably the simplest method to determine the permeability of fibrous preforms. The plain weave fabric showed a satisfactory saturation time (less than 9 min for 250 mm preform section) and permeability (5.66・10^-10 m²). The infusion process proceeded in a stable way and the resin front ran uniformly along the whole width of the preform. The chopped strand mat showed a saturation time similar to the plain weave fabric. However, it showed a very long time of saturation (over 46 min for 250 mm preform section) and low permeability (1.06・10^-10 m²) for the universal binder applied to the fibres. The universal binder probably does not react efficiently with terephthalate resins (ESTROMAL 14). The UD fabric showed evident anisotropy in permeability. When saturated along the main fibre strands, the permeability was by half higher than in the case of the plain weave fabric (8.2・10^-10 m²). When saturated transverse to the main fibre strands, it showed a permeability lower by about 40% in comparison to the direction along the main strands (4.65・10^-10 m²). The application of a spreading mesh considerably shortens the saturation time of the UD fabric (less than 1.5 min for 250 mm preform section), but it results in a deficient saturation. The PARABEAMR® fabric showed a lack of the “rising” effect in the VIP process. However, further investigations may show some applications for this structure in pressureassisted technological processes. The study showed that PAM-RTM software may be successfully applied to determine the permeability of fibrous preforms and to analyse the saturation processes. The determined values and trends in the K1 and saturation time are the initial assessment of preforms applicability in the vacuum infusion process.

In this study, organically treated montmorillonite was used as a filler for composites containing glass reinforced polyester waste. The composites were prepared by in-situ polyester polymerization when the organoclay was added to the reaction medium simultaneously with the monomers. The influence of the amount of nanofiller on the selected properties of composites with waste has been tested. In this work, composites composed of polyester resin Polimal 109-32K (product of Organika-Sarzyna) and nanofiller NanoBent^®ZR2 - organophilized montmorillonite (product of ZG-M “Zębiec” S.A.) have been obtained. The filler was introduced to the compositions in the amounts of 1, 2, 3 wt.% of all the components. The influence of the nanofiller on the density of the composites as well as on the compressive strengths and the flexural strengths of the polyester composites with a glass reinforced polyester recyclate was examined. There were presented the relationship between water absorption and soaking time for composites with different nanofiller contents. It was observed that an addition of 2 wt.% nanofiller NanoBent^®ZR2 to composites with 10 or 12 wt.% of recyclate causes an increase in the density and the strength. Styrene diffuses into the galleries of the organoclay montmorillonite easily, resulting in a decrease in the amount of styrene available for crosslinking in the medium, which decreases the chain length between the crosslink sites leading to higher strength. It was found that the composites with NanoBent^®ZR2 absorb less moisture than the unfilled ones.

In terms of applications, aluminum alloys share a larger fraction of Al-SiC composites due to their high wear resistance and different specific mechanical properties. Because of the increasing requirements of these construction materials, different methods of machining, including laser assisted machining, have to be recognized. In many publications one can find that the machinability of metal matrix composites is dependent on the temperature of the process. This paper describes the influence of laser beams on metal matrix composites. In particular, experiments, measurements of the surface temperature and microstructure analyses of an aluminum alloy reinforced by silicon carbide (Al-SiC) heated by a laser beam were carried out. The influence of a laser beam on the microstructures of machined samples was investigated and some mechanisms of surface layer alteration were discussed. It was noticed that the laser beam impact on the workpiece induced the immersion of the reinforced particles into the soft matrix.

The technology of sealing plates has been outlined, paying attention to the analogy and differences between this technology and rubber technology. The structure and micro-morphology of sealing plates were investigated by the methods of SEM, AFM and nanoindentation. An oscillatory rheometer was successfully used to examine the cross-linking course of the elastomer contained in the plate and accompanying phenomena. Significant differences were found between the courses of sulfur and peroxide vulcanizations. It has been observed that the rubber contained in the plate, after cross-linking, does not form a continuous phase but occurs in the form of isolated clusters, mostly including very thin membranes. There are also numerous visible agglomerates of fillers, especially in the middle part of the plate. It has been found that during plate formation and rubber vulcanization, a considerable temperature gradient occurs. The findings create conditions for the modification of sealing plate technology.

The surface nickel layers produced by the method of electrochemical reduction are used to protect the substrate material against abrasive wear and corrosion. The incorporation of dispersed phases such as lubricative polytetrafluoroethylene (PTFE) and hard silicon nitride (Si₃N₄) in a nickel matrix allows one to improve the tribological and corrosive properties. The aim of this work was a study of the influence of the deposition process parameters on the structure of the hybrid composite layers Ni/PTFE/ Si₃N₄ produced by the electrochemical method. The examinations included composite layers of the nanocrystalline nickel (Ni) matrix with the disperse phases of polytetrafluoroethylene (PTFE) and silicon nitride (Si₃N₄). The layers were deposited in a Watts bath at a current density of 5 A/dm², constant stirring rate of 500 rpm and constant phase content of PTFE (50 g/dm³) and Si₃N₄ (10 g/dm³). The stability of the suspension of the disperse phase in the bath, and uniform incorporation of its particles in the nickel matrix was provided by a cationic surfactant. Nanocrystalline nickel layers and nanocomposite Ni/PTFE layers produced by the electrochemical method were also investigated for comparative purposes. The aqueous dispersion of PTFE particles of a size of 0.1÷0.3 μm and polydisperse Si₃N₄ powder with rather different particle sizes were used to produce the composite layers. The topography and morphology of the silicon nitride powder and the structures of the produced nickel and composite layers were studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The structural analysis of the produced layers were performed and the crystallite sizes were determined with the X-ray diffraction method. The microhardness of HV 0.02 of the produced layers was determined using Zwick's tester. The completed examinations have shown that hybrid Ni/PTFE/ Si₃N₄ composite layers are characterized by a cohesive texture and nanocrystalline structure of the nickel matrix.

The paper analyzes the results of static tests conducted on fibrous composites. The strength characteristics were obtained for samples of different measuring length and different reinforcement architecture, produced by vacuum bag moulding and contact moulding using UDO^® E-type unidirectional fibreglass fabric as the reinforcement and HAVELpol.2 polyester or LH 160 epoxy as the matrix. Then, the experimental data were analyzed by applying advanced statistical apparatus to verify the assumptions about the normal and logarithmic-normal distributions of strength. The statistical analysis is essential to correctly develop a model to determine the strength characteristics of fibrous composites based on the Markov chain theory.

The microstructure and properties of 7475 aluminium alloy matrix composites - with additions of 10 wt. % of AlN powders of different particle size: < 40 μm, ~1μ m and < 1 μm were investigated. The composites were produced by means of powder-metallurgy. Pre-alloyed 7475 aluminium powders were milled with ceramic particles in a high energy planetary Fritsch ball mill for up to 40 hours and subsequently vacuum hot pressed at 380°C and 600 MPa. The microstructure of the obtained composites was studied using a metallographic microscope and scanning electron microscope (SEM). The performed investigations indicated good dispersion of ceramic phases. However, in the composite with the submicron AlN addition, a small tendency for agglomeration occurred. All of the composites were characterized by high density of intermetallic, Zn, Cu, Mg or Fe rich phases. Recrystallized Al grains were observed in the composite with the submicron AlN addition, indicating that the fine particles did not retard grain boundaries movement. The hardness of the consolidated samples was highest for the ~1 μm ceramic powder addition - nearly 320 HV in comparison to 250 HV for the finer powder addition. The compression tests showed 830 MPa of ultimate compression strength of the samples with the ~1 μm AlN particles, which was slightly higher than that with the submicron particles addition. The higher strength of the composites reinforced with the micro- rather than with submicro-particles suggests that the size of the ceramic phase addition can be considered as only one of the factors influencing the composite strength.

Polymer composites based on carbon fibers are used in a large number of applications in the environment of low temperatures. The current use of such composites is not limited to support structures but carbon/epoxy materials are also used successfully as primary structures in aeronautic applications. The paper presents the tensile properties of a AS7J carbon/epoxy laminate at low and room temperatures. The composite prepreg system includes epoxy M12 resin as the matrix and unidirectional high-strength carbon fibers as reinforcement. Tensile tests were performed at room temperature (RT), 223 and 153 K using an MTS 322.31 testing machine equipped with an environmental chamber. The strain gauge Vishay CEA-06-125UT-350 was employed to measure the strain. The tensile modulus, strength and Poisson ratio at different temperatures were compared. The failure analysis of the samples was investigated by scanning electron microscopy (SEM). F The fracture morphology at the interface between the fiber and matrix was also observed. The results have shown that the mechanical properties depend on temperature. The tensile modulus of the AS7J carbon/epoxy laminate increased as the temperature decreased, however, the tensile strength showed a slight decrease at lower temperatures. The value of Poisson's ratio fell slightly when the temperature decreased. The failure analysis of the specimens indicates that the nature of the destruction of the samples is also dependent on temperature. Classic morphology damage known as high-energy damage was observed in samples tested at room temperature and a more complex type of damage occurred in the samples at the temperature of 153 K.

The paper presents the static experimental testing of U-type (channel section) composite segments energy absorption. The segments have the overall dimensions b × h = 100 × 80 mm, rounded corners and damage initiators at their edges. The segments have been made in nine variants with respect to stacking sequence and laminate thickness. The matrix constitutes Polimal 104 N-1 P/p-503 polyester resin, i.e. elasticized and incombustible Polimal 104 resin produced by Organika-Sarzyna Co., Poland. Three types of stitched E-glass fabrics produced by Owens Corning Co., USA were used as reinforcement, i.e. D-610 (Weft 90° , uniaxial fabric [90], 607 g/m²), CD-600 (Biaxial, fabric [0/90], 610 g/m²), and CDDB-1200 (Quadriaxial, fabric [0/45/90/-45], 1213 g/m²). Static experimental tests were performed on a SATEC 1200 testing machine, with pressure force and punch displacement under registration (kinematic excitation at 2mm/min velocity). The failure processes were recorded using a PHANTOM v12 video camera. The tests were performed on segments of 400 mm or 200 mm length due to laminate thickness, using a problem-oriented test stand in which 5 composite panels were placed in parallel. The static testing of U-type segments energy absorption focussed on the quasi-optimal stacking sequence and thickness selection. In order to perform such investigations, the following optimization criteria were adopted: 1) failure level with respect to the following mechanisms: progressive crash, delamination failure, buckling failure, catastrophic failure; 2) maximum relative energy absorption. The tests performed for subsequent segment types have been illustrated with compression force vs. punch displacement curves. The figures showing segment failure mechanisms at selected positions of the punch are presented as well. The maximum values of compression force initiating the failure processes, absorbed energy and absorbed relative energy values are set up, with an estimation of the parallel failure mechanisms level. The energy values are calculated for punch displacements belonging to the interval 0÷50 mm. For further dynamic research, U/LE3 segments with a 8xD-610 stacking sequence and [90]₈ ply angles have been chosen as the authors’ preferred solution. These segments are characterized by the highest relative energy absorption, dominant progressive crash and F-s failure curve adjusted to a typical blast pressure impulse.

Fiber metal laminates are a new kind of hybrid materials. There are good candidates for advanced aerospace structural applications due to their high specific mechanical properties. The study researches the resistance to low-velocity impact of hybrid laminates based on aluminum alloys and a carbon/epoxy composite (Al/CFRP). These are completely new materials which have higher strength properties compared to other materials of this type (GLARE, ARALL), high fatigue strength, low weight, etc. The tested laminates were prepared by the autoclave method, which provides the best possible and repeatable quality of the received components. The laminates were analysed in terms of a comparison of their impact resistance according to different layer configurations and different energy levels. The laminates response to low velocity impact using a hemispherical tipped impactor (diameter 12.7 mm) were analyzed. The variation of the impact load as a function of force-time for different layer systems at each energy level was determined. After the tests, the damage zone was evaluated by using ultrasonic and image analysis methods. On this basis the dependencies of the damage zone area and maximum depth of the deformation depending on the layer configurations and energy level were determined. It was noted that Al/CFRP laminates are innovative materials characterized by high impact damage resistance (at low-velocity) because of the superior properties of both metals and fibrous composite materials with strong adhesion bonding. There is a combination of high stiffness and strength from the carbon/epoxy composite layers and good mechanical, ductile properties from aluminum. Generally, specific parameters such as incipient load (P_i), peek load P_m, maximum depth and damage area increased with impact energy. For lower impact energies (up to 10 J) and the first stage of the impact process, minor matrix cracking and delamination in the polymer composite and at the aluminum/composite interface may be observed. However, as the impact energy increased, fiber failures were observed to be the dominant damage mode. The first crack of FMLs (on the back side) was connected with the fiber directions in the finally layer of the carbon epoxy composite. The ply configuration (fiber directions) in Al/CFRP laminates has been particularly important for their impact resistance. The FML with (0/90) and ((±45) ply sequences in the carbon fiber reinforced composite have the best behavior followed by the (0) configuration.

The study develops the numerical modelling of a single rivetnut-bolt single-lap joint (RN-B) with in-plane and out-of-plane technological clearances, applied to joining longitudinal flanges of glass-polyester composite segments of tank covers. 3D modelling has been developed to simulate the RN-B joint tensile test aimed at determining the translational stiffness coefficients of the joint. Next, approximate 2D modelling of the RN-B joint tensile test has been developed using the translational stiffness coefficients (from 3D modelling and simulation), selected shell elements and the bushing-type bar element. The experimental validation test related to the RN-B joint tensile test has been examined up to full loss of load capacity. It has been proved that the translational stiffness coefficients in the elastic range (before joint failure) can be predicted correctly for a 3D joint model. The predicted stiffness coefficients can be applied in 2D modelling for the connections of shell segment flanges having the same stacking sequence of laminas. This approach is useful in engineering calculations and the design of glass-polyester laminate tank covers.

This paper presents the results of investigations on the thermoelectric properties of expanded graphite obtained by different methods. The expanded graphite was subjected to thermal treatment by two different ways: by rapid heating in a furnace and by irradiated microwave. For each of the methods, graphite was expanded in different conditions for the purpose of investigating the influence of thermal treatment on their thermoelectric properties. The bulk density and thermoelectric properties (Seebeck coefficient) of expanded graphite were measured. The results of the investigations show that the method and time of thermal treatment have a major influence on the thermoelectric properties of expanded graphite.

The goal of the paper is to present the process of preparing magnetorheological composite materials with thermoplastic matrices called magnetorheological elastomers (MRE) and the possibilities of modelling them using Kevin-Voight relations. At the beginning, the MRE components are presented: a specific thermoplastic elastomer matrix material and ferromagnetic fillers. Both polymer and iron particles are mixed together in specific proportions on the basis of of calculations of the Critical Particle Volume Concentration. Moreover, the method of mixing and the process parameters are described in this paper as they are crucial to achieve the desired structure of the composite. The next important step in testing the MR elastomer is preparation of the sample. At the beginning, the material samples are cut and mounted in such away as to be able to test the influence of magnetic and mechanical fields. Such material is cut into pieces and glued between claddings that support it during testing. The material is put simultaneously under the influence of a high temperature and pressure in a magnetic field in order to achieve an anisotropic structure. Tests performed on a hydraulic pulsator MTS allowed us to expose the MRE to various conditions, which gives better understanding of the behaviour of the material. On the basis of the results, it is possible to observe the viscous and elastic properties of the material and thanks to that, model it and simulate its behaviour, which is presented at the end of this paper.

The present study examines the impast of nanoceramics on the structure and selected mechanical properties of intermetallic alloys. In order to determine the grain size in the different variants of materials, with LENS fabricated Fe40Al, an equivalent mean diameter was determined. Resistance against oxidation of the material with and without the addition of nanoceramics was also determined. Observations of the microstructure and phasal analysis did not reveal the presence of nanoceramics in the bulk of the material. However, it was found that the addition of nano-oxide ceramics, increases the grain size and a 4-fold increased heat resistance compared to the reference material. For the alloy without the addition of the oxide nanoceramics, a relative deformation of 2% at a lower yield than the 2% composite Fe40Al vol. n-Al₂O₃ was reported. An attempt to explain the situation it was based on research using the Thermal Imager, which is equipped with a LENS MR-7. It allowed permanent registration of the temperature distribution and weld puddle determining a number of thermodynamic dependences. It additionally drew attention to the fact that during the manufacturing process, differences between the width of the liquid metal mesh for the alloys with and without nanoceramics was observed. It indirectly proves the existence of ceramics on the surface of powder particles at the time of melting the base material, and probably there where an increase in the width of the weld puddle was observed.

This paper presents the results of studies on the electroless deposition of Ni-P/nano-Al₂O₃ composite coatings on pretreated polymeric bases (PET polyester Mylar A type) and on carbon fibres (24k fibres with 7 µm Tenax rovings). The Ni-P matrix was deposited from a solution consisting of NiSO4 0.1 M; NaH2PO2 0.2 M; glycine 0.21 M, with a pH = 7.5÷8.5 and thiourea added as a stabilizer, as well as cetyltrimethylammonium bromide as a surfactant. Aluminium oxide C (DNC - Degussa, grains 13 nm) or A16 (Alcoa, grains 400 nm) were powders amounting to 10÷30 g/l, with ultrasonic homogenization of the suspension. Under the experimental conditions applied, partial sedimentation of the A16 powder occurred, thus a further study on carbon fibres metallization was performed with the use of the DNC nanopowder. Deposition was performed in the temperature range 60÷70oC, during 5÷60 minutes, while the bases rotated at 1 rpm and the suspension was agitated with a stirrer. The composition of the deposited layers was determined by chemical methods and their surface morphology was investigated using SEM. A procedure for the preparation of the PET substrates for the tests was set out to obtain good adhesion of the Ni-P layers. Under the applied conditions, Ni-P/Al2O3 layers of a thickness within 130÷720 nm, aluminium oxide content up to 25% by weight, and 2÷4% phosphorus by weight were obtained.

The possibility of producing polystyrene-bonded micro-magnets with the use of two commercial nanocrystalline Nd-Fe-B powders (delivered by the Magnequench Co) was examined. The micro-magnets were formed by the injection method to obtain gear-shaped samples. The powders were produced by two different methods, namely the crushing of a rapidly cooled ribbon (MQP-16-7) or spraying (MQP-S). Depending on the production method, the powders differ in their particle shapes: the former method gave flaky particles whereas the latter - spherical particles. The particle shape has an essential effect upon the technological properties of the powder. The gear-shaped micro-magnets with a diameter of 2.6 mm were examined by X-ray tomography. An analysis of the 3D images has shown that during their injection with polystyrene, the powders undergo segregation. The largest particles of the MQP-S powder (spherical) are located at the greatest distance from the injection point which was positioned in the axis of the gear. They are also relatively numerous near the side surfaces of the gear. The filling ratio of this composite decreases as we pass along the radius of the gear. Taking into account the fact that the properties of the sprayed powders depend on their particle size, these observations will permit the of designing pieces with a gradient of magnetic properties. In the gears produced from the powder with flake-shaped particles, the flake surfaces tend to position themselves perpendicularly to the gear radius. The shape, therefore, of the powder particles determines the anisotropy of their distribution within the product. This observation can be utilized in the design of bonded magnets.

Zirconia micropowder stabilized with 3 mol% yttrium oxide is used to produce bisques, being the pre-sintered blanks intended for the manufacturing of all-ceramic dental restorations. The bisques should be characterized by mechanical strength and fracture toughness suitable for the precise milling of thin-walled items afterwards sintered to full density, ensuring good performance. The aim of this research was to study the effect of a 0.2 mass% nano- Al₂O₃ addition to the TZ-3Y Tosoh powder on its behaviour during low and high-temperature consolidation, and on the properties of green compacts, bisque-sintered and fully-sintered TZP materials. The bisque-sintered materials were manufactured at 500÷900°C, and characterized in terms of their densification, mechanical strength, hardness and fracture toughness, and compared to the Cercon and ICE Zirconia green materials. The materials sintered at 1200÷1550°C were analysed to show the influence of the alumina addition and presintering temperature on the densification and microstructure. Comparison was also made to sintered bodies derived from the Cercon and ICE Zirconia materials. Both unmodified and Al₂O₃ modified TZ-3Y powder can be used for the fabrication of bisques for dental applications. An increase in strength and hardness of the bisques with a pre-treatment temperature was observed, and it significantly affected their behaviour during milling; the bisques pre-sintered at 700 and 900°C showed the best machining properties. The addition of 0.2 mass% nano-Al₂O₃ to the TZ-3Y powder contributed to lowering the final sintering temperature, and to obtaining a microstructure analogous to the Cercon derived one.

The article presents the approach for damage characterization in composite aerospace structures for the ultrasonic non destructive evaluation technique. The damages which affect the structural integrity of such components are the following: disbonds, delaminations, foreign object inclusions and many others. Different NDE techniques are used for the characterization of composite structures. There are numerous limitations and advantages of each technique. One of the most suitable techniques for that purpose is the ultrasonic one. The most important issue in that method is proper selection of inspection parameters and the next issue is signal processing. The approach to signal processing may contain analysis in the frequency and time domain of one and two dimensional signals. Moreover for the size of the damage evaluation, the amplitude (signal value) is used very often. In the article, the 2D signal value evaluation approach is presented. The article will highlight the problems and advantages of signal processing and will show new possibilities of 3D composite characterization (e.g. ply stacking sequence).

The article deals with the problem of investigating the correlations between the loading rate and absorbed energy capability dependence of composite energy absorbing structures. Energy absorbing structures dissipate impact kinetic energy by means of crushing their structure. Numerous investigations have been conducted to evaluate the dependence between the loading velocity and Energy Absorbed (EA) for composites, however, the results are quite different and sometimes inconsistent. The material properties defined during static tests are possible to be applied at the initial stage of numerical calculations. More advanced and accurate target simulations require data from dynamic load tests. Single energy absorbing elements and three-element energy absorbing structures were subjected to static and dynamic investigations. The single energy absorbing elements were tube-shaped and built of epoxy composites reinforced with glass fabric. Fragments of sandwich energy absorbing composite elements were prepared from three tube elements arranged symmetrically on an equilateral triangle plan and stuck between composite plates. Static and dynamic energy absorbing tests were conducted. The specimens were loaded statically on a tension machine - Instron 8802. The specimens were compressed at a constant load velocity equal to 40 mm/min (0.0007 m/s). The dynamic tests were performed on a spring impact hammer. The impact load velocity was about 6.0 m/s. Based on the obtained results, it was concluded that the load velocity of a glass/epoxy composite specimen crush leads to an EA decrease. B The behaviour of both single energy absorbing elements and multi-element fragments of energy absorbing constructions was compared.

Determination of the influence of processing and annealing on the change of thermal properties, structure, color and gloss for samples made of a polyamide 6 composite with glass beads was the aim of this work. Investigation of the crystallinity degree using the DSC method as well as investigation of the structure using optical microscopy have been made. The color change was determined by the CIELab method and the gloss by reflection at the angles of 20 and 60°. Investigations into the influence of the conditions of injection moulding on the properties of the PA 6 composite with glass beads, commercial name of Schulnamid 6 GB30H, have been conducted. The samples were injected using a KraussMaffei KM65-160C1 injection moulding machine. Investigations have been conducted for the samples before as well as after annealing. The highest value of the crystallization degree of the PA 6/glass beads composite was obtained at an injection temperature of 280°C and mold temperature of 100°C. During annealing, an increase in the crystalline phase content for the PA 6 composite with glass beads occurred. The increase in the lightness value after the annealing process of PA 6 filled with glass beads was obtained. The character of changes of the a* and b* coordinate values for the examined materials before and after the annealing process was evaluated, which proves the essential influence of the conditions of injection moulding and thermal treatment on the colour change.

The paper presents the research results on the dynamic load resistance of ceramic matrix composites with aluminum spatial skeleton reinforcement, particularly focused on the ability to absorb impact energy. In the considered cases, the composite composition was complemented with a liquid additive. The addition was designed to improve impact energy absorption. The matrix of the composite was simultaneously a foundry core of skeleton casting. Internal channels which reproduce i trusses were created with the use of specially designed templates. The use of ceramic shapes allowed the authors to obtain strong cores with complex geometry, which act at the same time as the composite matrix, influencing its mechanical properties. Strength tests with a dynamic load were performed. The energy absorbed by the composite material was determined. The research was conducted on a specially-designed stand. The concept of the stand was developed based on drop weight tests.

The three-point bending test has been performed for a single-wave glass-polyester laminate segment. The geometry and stacking sequence of the segment is modelled on a selected composite tank cover. The main purpose of the study is to develop numerical modelling and simulation methodology for such a test using FE code MSC.Marc/Mentat as well as to perform experimental validation. The segment was manufactured in ROMA Ltd., Grabowic, Poland and made of a glass-polyester mixed laminate with a (CSM450/STR600)4/CSM450 stacking sequence, using contact technology. The elastic and strength constants of the laminas have been derived experimentally on standard specimens cut from homogeneous laminates M (5xCSM450) and F (4xSTR600). The laminate components constitute: Polimal 104 polyester resin (matrix; produced by Organika-Sarzyna Co., Poland), E-glass mat and E-glass 1/1 plain weave fabric (reinforcement; produced by KROSGLASS Co., Poland). The numerical tests include the application of six selected shell finite elements, which accept layered composite material declaration, available in the MSC.Marc FE library. Simulated pressure force - punch displacement diagrams are presented against the respective experimental results. It has been pointed out that Element_75 (Bilinear Thick Shell) gives the results closest to reality, both qualitatively and quantitatively. A set of options/values of numerical modelling and simulation parameters elaborated by the authors’ team in earlier papers has been applied. Index failures contours related to subsequent laminas are recommended for the design of shell segments of laminate covers of tanks and canals.

In this work we present the preparation of 2 and 12 vol.% zirconia alumina composites via filter pressing and pressureless sintering at a constant heating rate (CHR), by means of two-step sintering (TSS) and reverse two-step sintering (RTSS). Nanozirconia (10 nm) and microalumina (175 nm) powders were used. The resultant composites were characterized in terms of their microstructural (density, grain size) and mechanical (hardness, fracture toughness) properties. The heating schedule showed an insignificant effect on the density of the composites. TSS produced composites of the best properties and finest microstructure, while RTSS in the case of samples containing 12 vol.% of zirconia, produced the coarsest grains. The resultant densities were close to 95%, but the fracture toughness and hardness were reasonably good: (7.0±0.2) MPa•m^0.5 and (20.8±0.2) GPa for the TSS sample containing 12 vol.% zirconia, respectively.

Currently, much attention has been focused on the development of ceramic composites with metallic particles due to their higher strength as well other properties compared to monolithic ceramic. Traditional methods of powder metallurgy are not capable of obtaining composite materials products of any shape in an uncomplicated way. For this reason, attempts have been made to adapt the gelcasting method (initially used only for ceramic powder) to obtain cermets. In the paper, the results concerning alumina-nickel ceramic composites fabrication via the gelcasting method are presented. The paper presents the effect of the addition of nickel on the polymerization time of composite slurries. The characteristics of selected physical and mechanical properties of composites containing 5 vol% and 10 vol% of nickel have been described and compared to the results achieved for 100% Al₂O₃. Tests were conducted for the green body and for sintered samples. Observations of the microstructure of the produced Al₂O₃-Ni composites are also presented. Computer image analysis was performed for the nickel particles in the composites. The obtained results confirmed the possibility of applying the gelcasting method for the preparation of alumina-nickel composites.

Determination of the influence of the colloidal nanoparticles of zinc oxide additions on the properties of water glass, a binder of moulding and core sands - is the subject of the paper. The nanoparticles of zinc oxide in various suspensions were introduced into water glass and the adhesive properties were examined by measuring the quartz wettability by the binder. The binder-matrix interactions were verified by strength tests of loose self-setting sands with modified binders. The most efficient quality improvement of moulding sands with water glass can be achieved by the binder modification. Multimolecular components such as polyphosphate, polyacrylamide, carboxymethylcellulose, and polyvinyl alcohol have been used up to now as modifiers. They differed in: their polymerisation degree, molecular mass, kind and number of functional groups. The performed investigations of water glass modification by the suspension of ZnO nanoparticles in ethanol and in propanol indicated that strength R_m^u of loose self-setting sands with water glass modified by the suspension of ZnO nanoparticles in ethanol and in propanol (without a chemical hardener) increases when the modifier is added. In the case of adding the modifier in the form of a suspension of ZnO nanoparticles in propanol - sand strength R_m^u increases by approx. 8% (when modifier addition equals 3 mass %) and by approx. 26% (when this addition equals 5 mass %), whereas when the modification is carried out by the suspension of ZnO in ethanol - sand strength R_m^u increases by approx. 18% (when modifier addition equals 3 mass %) and by approx. 12% (when this addition equals 5 mass %).

The viscoelastic behavior of polymers is normally studied by chemical engineers to monitor the progress of various molecular phenomena, such as: chain scission (driven by oxidative degradation and hydrolysis), viscous flow, as well as molecular relaxation. Mechanical engineers usually enter the arena of viscoelastic modeling when analyzing the damping properties of the materials, or when considering energy dissipation mechanisms. Available viscoelastic models however, allow for more detailed studies, which cover the response of polymers subjected to a complex load history, with different thermo-mechanical conditions. It is especially important when strains and stresses in real, industrial products of high quality must be investigated. In this paper, the experimental and numerical results of the complex viscoelastic behavior of the CY228 epoxy system are presented. The concepts of time-temperature superposition and the Master Curve, as well as the generalized Maxwell model and WLF equation are recalled, and applied to a stress-strain analysis of the composite under consideration. It was shown that detailed measurements of viscoelastic properties allow for very accurate modeling of the composite mechanical response.

Ceramic-polymer composites with ferroelectric properties provide significant opportunities in the design and manufacture of modern electronic materials whose functional characteristics are constantly being improved. Barium titanate (BT) and barium strontium titanate (BST) are known and widely used materials in electronics. The paper presents the results of research on a receiving ceramic-polymer composite with an as low as possible permittivity and loss tangent. As a ceramic fraction barium-strontium titanate (BST) with various dopants (Fe₂O₃, Ni₂O₃, La₂O₃, SnO₂ and Y₂O₃) were tested and as an organic one - water dispersions of styrene-acrylic polymers. The influence of BST doped with metal oxides on the sintering process was observed. X-ray diffraction patterns were made for sintered powders while the Vickers hardness, relative density and volume shrinkage of sintered pellets were studied. The zeta potential as a function of pH for pure BST and doped with Ni₂O₃ were measured. BST doped with Ni2O3 had the best relative density and this powder was used for further research. For the aqueous tape casting method four water dispersions of polymers with different concentrations and structures as binders were tested. For these polymers heat flow as a function of temperature by differential scanning calorimetry (DSC) and the glass transition temperature were measured. Additionally, the concentration of water dispersion of the polymers was tested by the gravimetric method. For the obtained ceramic - polymer composites, the relative permittivity and loss tangent were measured at a 9 GHz frequency.

This article deals with the possibility of simulating composite models in CAD software. The first part of the paper deals with information about composite material, the types of fabrics, types of laminates and the properties of layers. Then a suitable part was chosen and a model was created for the next analysis. The main reason for choosing carbon fiber as the material for the new part is due to its low density and high tensile strength. The weight of the part made from a carbon fiber composite is also smaller than from classic materials like aluminium. At the end of the paper, external loads are simulated on the composite model and the criteria of failure are defined.

The paper presents the preliminary results of research on the surface modification of ceramic composite materials. This modification can be done by introducing particles of ceramic powders with a high value point of zero charge. The functioning of the new membranes can be described as electrostatic adsorption of particles imitating viruses onto an oppositely charged filter surface. The purpose of this study was to design ceramic composite materials with active layers. The first stage of this study was to shape porous ceramic composite materials by pressing by means of a hydraulic press at the pressure of 30 MPa. In the next stage, a way of obtaining an active layer of the filter and an impregnation method were designed. In the research diatomaceous earth and bentonite were used while polyvinyl alcohol was the binder. The samples prepared during the study were subjected to impregnation with magnesium acetate. In the study, polymer dispersions with negative electrokinetic potential - Rokryl SW 4025 and SW 115 - were used to stimulate the process of filtration. The properties of the sintered samples - tensile strength, open porosity and pore diameter distribution were investigated. The microstructure of the obtained samples was examined using a scanning electron microscope. The zeta potentials of the obtained ceramic composite materials with active layers and polymer dispersions were established using a zeta potential analyzer. On the basis of the measurements and filtration test in which polymer dispersion simulated viruses in water, it was discovered that the modification of ceramic materials surfaces gives good results. In the samples, the particles of polymer dispersions were attracted to the walls of the filter. The permeates after being filtrated through the impregnated samples become transparent. MgO, which was obtained on the surface of the ceramic composite, plays the role of promoter in the process of the adsorption of negatively charged particles imitating viruses.

The residual stresses in thermally sprayed coatings are of great interest since they affect the reliability of the coating/substrate system. The evaluation of residual stresses in thermally sprayed composite Ti+Al₂O₃ coatings on Al₂O₃ ceramic substrates has been conducted. The purpose of the research was to measure the residual stresses generated in coatings deposited by detonation gun thermal spraying and compare the results obtained for pure titanium and Ti+30% Al₂O₃ composite coating. The stresses in deposited coatings have been obtained from the curvature measurement of the analyzed samples. A measuring system has been built for this purpose, which allowed registering of the curvature of the coated samples. The residual stresses have been calculated from the measurements using the Stoney equation and compared with the results obtained from the modified Stoney equation derived by Clyne. It was observed that tensile residual stresses are formed within the coating and grew with the coating increase. The applied stress calculation formula showed that for higher coating thicknesses, the primary Stoney equation underestimates the results comparing to the modified Stoney formula (Clyne).

The main advantage of ceramic-metal composites is the increase in fracture toughness of the brittle ceramic matrix. The slip casting moulding method is widely used in the ceramic industry, which gives the possibility to obtain products of complicated shapes without green machining. Good quality and homogeneity of powder consolidation are crucial in the ceramic and ceramic matrix composite fabrication process as they influence the properties of the material. In the paper, the results concerning ceramic matrix ceramic-metal composite fabrication via the slip casting method are presented. Composites were formed from a slurry containing alumina and metallic nickel particles. For the studies nickel powder of average particle diameter below 1 µm was used (Aldrich; d = 8.9 g/cm³). Two types of alumina powder were applied. The materials formed from alumina powder of an average particle diameter of 0.4 µm (α-Al₂O₃, A16SG, Almatis; d = 3.9 g/cm³) were sintered at a temperature of 1550°C (above nickel melting point; T_mNi = 1455°C), whereas composites obtained from alumina powder of an average particle diameter of 0.2 µm (α‑Al₂O₃, TM‑DAR, Tamei, Japan, d = 3.8 g/cm³) undergo densification already at 1300°C (below nickel melting point). The mechanical properties of the composites are dependent on the processes occurring in the sintering process, during which coalescence may lead to the growth of nickel particles. Stereological analysis of the nickel particles in the alumina matrix (in composites sintered below and above nickel melting point) was performed. The description of nickel particle growth in accordance to the sintering temperature was correlated with mechanical properties of the composites.

The main aim of this paper was to investigate the effect of sintering temperature, sintering time and reinforcement particle size on the properties of Al-Al₂O₃ composites. Three sintering temperatures were applied: 500, 550 and 600°C for 30, 60 and 90 minutes. Experiments were performed using specimens containing 0, 5 and 10% of alumina. The average particle sizes of alumina were 2, 10 and 20 [xml:1:97de3e3486]μ[/xml:1:97de3e3486]m. The investigated properties included relative density, hardness and compressive strength. Microstructural observations showed that Al-Al₂O₃ composites could be successfully formed for all of the studied combinations of sintering temperature, sintering time, alumina particle sizes and amount of reinforcement. The relative density of all the composites increased when the particle size of alumina was reduced. The highest relative density was obtained at 600°C. Higher hardness and compressive strength were observed in samples containing finer Al₂O₃ particles. The variations in hardness and compressive strength of Al-Al₂O₃ composites were dependent on the sintering temperature and time. Increasing sintering time at 500 and 550°C led to a gradual increase in hardness and compressive strength. Similar results were obtained as well after sintering at 600°C when the sintering time was increased up to 60 minutes. A prolonged sintering time up to 90 min had a contrary effect on the hardness and compressive strength of the composites.

Silver base composites intended for electric contact materials with additions of 20% of amorphous phases based on zirconium or nickel good glass formers were consolidated from ball-milled powders. The structure was investigated using X-ray diffraction and TEM. The consolidated samples show an increase in hardness with an amorphous phase addition which is of the order of 100 HV for 20% of the amorphous phase. SEM and TEM structure studies have shown a nanocrystalline grain size in silver after milling and nanocrystalline intermetallic inclusions in the amorphous phase after hot pressing. DSC studies have shown a crystallization peak, confirming amorphization of the powders. The composites have shown a similar loss of mass during 50 000 contact operations, like conventional Ag-W composites. Another type of additions used to form aluminum alloy base nanocomposites was the amorphous powder of the alloy Al10%Ni10%Ti10%Zr (in at.%). Almost complete amorphization was observed after 60 hours of milling. TEM investigations allowed us to identify nanocrystalline intermetallic phases in the milled powders. The microhardness of the powder was very high - near 500 HV. Similar to the other types of composites, some growth of aluminum solid solution grains was observed and only a slight increase in the size of intermetallic phases was noticed. The compression strength was slightly lower than for aluminum alloy based ceramic composites due to crack formation in the amorphous phase.

A porous skeleton of TiC carbide was successfully fabricated by combustion synthesis ignited in a microwave field. The synthesizing temperature has been remarkably affected by the time of ball milling or positioning in a single mode microwave reactor. The combustion products were characterized by XRD and SEM investgatons. To moderate the reaction and avoid the explosion mode, an aluminium powder was added to the mixture. The prepared TiC, Al-Ti-C skeletons were next infiltrated with an AlSi12 aluminium alloy by the squeeze casting method. The composite materials exhibited a relatively homogeneous microstructure with low porosity.

The results of vibration welding of glass fibre reinforced nylon 66 (TECAMID 66 GF30) are presented in this paper. The aim of the investigation was to determine the influence of the welding parameters on the quality of joints, which was conducted on the basis of light and scanning electron microscopic examinations as well as tensile tests. The results showed the influence of the vibration welding process on the way of creating the joint, on the material continuity, the orientation of the glass fibres in the welding area and on the joint strength. The joint is created as a result of joining the matrices of two welded materials. The glass fibres in the welding area are oriented in the direction of the vibrations and into the flash. A high tensile strength of joints is possible to achieve in a wide range of welding parameters.

The scope of the study is the experimental evaluation of the effect of the main characteristics of fabrics used as a reinforcement of polymer matrix composites on the mechanical performance of composites. The characteristics taken into consideration are: (1) fibre material - Kevlar, carbon, glass, (2) areal weight - 90 and 300 g/m²; only for glass fibre, (3) reinforcement form - plain weave fabric, chopped mat; only for glass fibre, (4) weave type - plain, twill; only for carbon fibre, (5) tow size K - 2, 3, 12; only for carbon fibre. Static flexural tests were conducted for all the specimens. The flexural strength (R_g), flexural modulus (E_g) and the strain by maximum load obtained during bending (Epsilon) have been determined. It was found that the material of reinforcing fibres has an essential effect on the mechanical performance of a laminate. Laminates reinforced with carbon fibres had/obtained/achieved thegreatest R_g and E_g. Glass-reinforced (GFRP) laminates performed slightly better in comparison to Kevlar-reinforced ones. However, the Kevlar-reinforced laminates showed the highest deformability at high load. An increase in areal weight of a reinforcing fabric causes a growth in the R_g and E_g and a decrease in deformability of a GFRP laminate. The reinforcement form evidently affects the mechanical performance of a laminate. The GFRP 0/90 fabric reinforced laminate showed an R_g half higher in comparison to the equivalent chopped-matt reinforced one. The twill carbon fabric FRP laminate showed a slightly lower R_g and E_g, whilst a bit higher deformability in comparison to the plain weave carbon fabric FRP one. The tow size K practically does not affect the strength or deformability of a CFRP laminate. However, an increase in K causes a drop in the elastic modulus of the composite.

The most frequently used methods for manufacturing composite castings with an internal structure composed of a metal matrix and solid particles of the reinforcing phase are gravitational casting (into disposable or permanent moulds), pressure die casting, squeeze casting and centrifugal casting. The diphase character of the composite suspension designed for casting leads to the fact that its gravitational casting is delimited, among others, by a minimum thickness of the casting walls. The process of casting composite suspensions using the centrifugal method is unavoidably accompanied by migration of the reinforcing phase particles. It means that during the casting process, the particles move with respect to the liquid metal matrix. Therefore, experimental tests have been made with a view to manufacturing composite castings with the method of centrifugal casting. The tests were aimed at answering whether thin-walled castings may be manufactured using this method and checking the effect of the method on the behavior of the particles present in the cast suspension. The tests have been performed using a standard composite material with an aluminum alloy matrix including silicon carbide particles. The cast part was a small turbine with a blade thickness of about 1 mm. The casting moulds were made from a gypsum mass which was poured in a device composed of an induction furnace and a mechanism, referred to as a caster, that ensured rotation of the mould around a vertical rotation axis. The castings obtained in such way were evaluated with regard to matching the required shape and achieving a uniform distribution of the reinforcing phase in the composite material samples cut from various points of the casting and its gating system. It was found that the casting conditions allow one to obtain thin-walled castings, however, migration of the reinforcing phase particles in the cast suspension is significant. Hence, further research of the conditions of applying the method appeared necessary.

This paper deals with the results of an experimental study of the occurrence of the self-heating effect during cyclic fatigue loading of plates made of polymeric composites. The evolution of self-heating temperature distributions was registered by infrared camera from the beginning of loading till the breakdown of the specimens. During the experiments it was observed that the process of thermal fatigue of the composite elements could be divided to three phases. It was observed, that on the transition border of the second and third phases of thermal fatigue, a crack initiates, which is caused both by increasing the self-heating temperature and mechanical fatigue. This moment corresponds w to the value of self-heating temperature, which is critical for given loading parameters. The critical self-heating temperature is strongly dependent on the excitation frequency, which results from the tim-temperature superposition principle. The influence of the excitation frequency and length of the specimens on the value of critical self-heating temperature was investigated. Based on experimental data, the empirical model of thermal fatigue, which uses the master curve of dynamic storage modulus, was proposed. The obtained experimental results and proposed fatigue model could be used in operation and structural health monitoring problems for the prediction of critical loading parameters of elements made of polymeric composites.

The paper presents the chosen results of investigations on polymer flow during the mould cavity filling phase of the injection moulding process. The process is characterized by high dynamics, which causes several technological difficulties, both during injection mould design and during product implementation to the production stage. Greater understanding of the phenomena which occur during filling of the injection mould may lead to more effective design of processing tools and shortening of the time for implementation and production time. The results of computer simulations of the injection process have been compared with the results of video recording of the plastic flow during the filling phase. A specialized injection mould which enables observation and registration of the plastic flow during processing has been employed. The mould enables direct monitoring of the course of the phenomena inside the mould cavity in two planes. Transparent sight-glasses have been used, made of a material called Zerodur® which is characterized by a coefficient of thermal expansion close to zero. To record the flow, a digital video camera has been employed. The camera enabled registration of the flows with the rate of 25 fps. This reduced the scope of the investigations, since at higher plastic flow speeds the registered image became less clear. The video sequences registered during the investigations were later digitally processed in order to ensure in-depth analysis. For the simulation investigations, professional computer software, Autodesk Moldflow Insight 2011, has been employed. The results of the investigations enabled the documentation of specific phenomena which occur during the plastics or their composites injection process. The registered video sequences have been compared to the results of numerical calculations and then it was estimated to what degree the computer simulation of the injection process may be useful in practice. The investigations were performed on a wide scale, however, only chosen results have been presented. As an example, the issue of flowing around a rectangular obstacle of the plastic stream has been described. The obtained results of the investigations are so encouraging that they made the authors continue such experiments.

The paper presents a method of casting metal matrix composite materials based on light alloys reinforced with cenospheres. The cenospheres, which are a product of fly ash processing by flotation, were formed into porous ceramic shaped elements and subjected to pressure infiltration with a liquid metal on a specially designed hydraulic press. The infiltration process was recorded with an infra-red camera. The obtained composite samples have been tested with the following inspections: density and hardness, X-ray and microstructure. The thermography inspection showed the temperature distribution on the surface of the preheated ceramic preforms. The X-ray examination revealed in the castings a few cracks caused probably by a high value of squeeze pressure. Numerous spheres filled with a solidified metal in the microstructure images were observed. The degradation of the cenospheres was directly connected to the infiltration process parameters, namely: the temperature of the preform and molten metal, too high squeeze pressure or too invasive process of the preform preparation. Despite the anticipations, only a slight decrease in composite density in comparison to the density of the monolithic alloy has been found. However, an increase in the composite hardness has been observed. As a result of the described work, instructions for further tests, which involve slight changes in the process parameters namely: casting pressure, temperature of the molten metal and the ceramic preforms, in order to achieve proper structural and mechanical characteristics of the composite products have been established.

Simulations of the injection moulding process of polypropylene with a glass fibre content were conducted using special software - MOLDFLOW PLASTICS INSIGHT ver. 4.1. A seven - parametric rheological Cross - WLF model was chosen for the research. For holding phase simulation as well as to determine the inner stresses and deformation of the parts, the pvT dependence should be known. The Tait equation was used in the numerical calculations. In the first step of the simulation a solid model of the part was created using the Master Modeller modulus of I-DEAS NX software. A sample for cracking resistance tests, of the SENB type, with runners was modelled. Then the cooling conditions were introduced to the program. The next step modelled the injection mould geometrical shape and mesh creation. The crucial moment in the simulation is the introduction of the data describing the processed polymer properties. They were the thermal properties as well as the rheological and mechanical properties of the injected composite: PP with a 25% glass fibre content. In the next step, the processing conditions were entered into the simulation program (Moldflow Plastisc Insight ver. 4.1). The simulation research was conducted on the basis of the design of an experiment that was prepared with the use of Statistica 6.0 software. The changes of four processing parameters were taken into account: holding pressure, injection temperature, injection velocity and mould temperature. The simulations were made for extreme values of these parameters. The results of the numerical simulations of the residual stresses and strains on the injection moulded parts are presented graphically and conclusions were drawn from them.

The numerical calculations made in the work included the analysis of stress distribution near the rift top and determination of the stress intensity coefficient (WIN) as well as the J integral during three-point bending of SENB samples made from composites with a matrix of two well-known thermoplastics: PP and PA6 with a 25% content of glass fibre. Analysis of the composites crack development and propagation was also done performed. The numerical tool used for FEM calculations is the ABAQUS/Standard computer program that has modern calculation procedures in this field. The numerical calculations were made taking into consideration the experimental data determining the conditions of cracking process initiation of the composite material. The results of the numerical calculations were verified by the results of the experiments. The numerical calculations that were made concerned a geometrically non-linear problem. They were conducted with use of the incremental-iterative Newton-Raphson method. The numerical analysis was performed in two steps. The first step was a preliminary analysis that allowed estimation of the stress level in the composites near the rift top that initiated the cracking process, as well as forecasting the possibility of further propagation occurrence (or exclusion of this phenomenon) in the material region. In the second step of calculations corresponding to the critical value of deflection, numerical calculations taking into account the development and propagation of the crack were made using a more advanced technique for modeling cracking - the Cohesive Zone Method (CZM).

The load adapted design of complex lightweight bar frame works with nodes and branched profiles is a significant challenge from both the structural mechanical and the manufacturing point of view. The search for novel material efficient solutions increasingly leads to the use of fibre-reinforced composites as they exhibit good specific material properties and a high degree of design flexibility. In order to achieve an optimum design of thin-walled, branched, hollow composite structures, a bionic approach following the top-down principal is pursued and simulations of various Y- and T-shaped models are carried out. The typical characteristics of the ramification areas of selected plant structures are analysed using micro-mirror fringe projection and micro-computed tomography. The scientific findings of plant morphology gained by these analyses are transferred into FE-models for structural analyses and parameter studies. The anisotropy of fibre material, the morphological characteristics of the examined cacti and the technological restrictions of the braiding process are considered in the design process of simulation models. The results show a significant increase of stiffness of thin-walled branched models with bioinspired design features compared to models constructed according to the state-of-the-art technologies.

Aluminium alloys reinforced with carbon fibres can find applications in a variety of light constructions operating in complex load conditions. The methods of obtaining these types of composites are mainly based on liquid-phase methods, where the connection between the composites is achieved as a result of wetting the reinforcement phase with a liquid metal. For these processes, the aluminium matrix should be characterized by high strength, the possibility for heat treatment and adequate technological properties (high castability, good wettability of carbon fibre surface by molten metal). A following important aspect in the Al/CF discussed system is a reduction of reactivity between the liquid aluminium and carbon fibre. In the article, the results of infiltration tests on nickel coated carbon performs by a liquid Al alloy have been presented. In the examinations, aluminium with a silicon alloy (226D) modified by magnesium and strontium were used. The infiltration process was carried out on a Degussa press. The manufactured composite plates were characterized a regular shape, without surface casting defects. The nickel coating prevents the destruction of the fibres, but the reaction of Ni with the liquid aluminum alloy in the boundary area leads to the precipitation of a ductile phase of the Al-Ni system. Decohesion takes place among the matrix and fibres, which allows the supposition that the composite will be characterized by good mechanical properties. This requires experimental verification, which is planned in the successive stage of the research in the project “3D-textile reinforced aliminium matrix composites (3D-CF/Al-MMC) for complex stressed components in automobile applications and mechanical engineering” in the frames of the programme supported by the Polish Ministry of Science and Higher Education and by the DFG in Germany in the Polish-German Bilateral Project.

In this paper, the technology of AlSi12Cu2Fe/Cr_xC_y in/ex-situ composites produced with Cr30Fe8C ex situ particles is described. The composites were gravity cast, applying simultaneously an electromagnetic field. The purpose of the investigation was to analyse the influence of the frequency of an electromagnetic field on the segregation, quantity and morphology of the reinforcement phase in an aluminum matrix. The technological concept is based on the assumption that the added chromic-iron particles dissolves in the aluminum matrix and the carbide phase becomes the reinforcement of the composite with a variable portion of Al-CrFe intermetallic phases. On the basis of microstructure observation, the quantity, segregation effect, morphology and the volume fraction of the different phases in the composite material was assessed by microscopical analysis.

The constantly rising demands for lightweight structures, particularly in traffic engineering as well as in machine building and plant engineering, increasingly require the use of continuous fibre-reinforced composite materials. These materials, due to their selectively adaptable characteristic profiles, are clearly superior to conventional monolithic materials. Especially composites with textile reinforcement offer the highest flexibility for the adaptation of the reinforcing structure with regard to complex loading conditions. This paper presents the procedure and evaluation of a gas pressure infiltration process (GPI) for the manufacture of carbon fibre-reinforced aluminium metal matrix composites (CF/Al-MMC). Furthermore, the development of a new furnace for a modified GPI method is presented. In order to verify the new design, numerical simulations of the heating in the furnace chambers were prepared, which finally formed the basis for the improvement of the furnace as well as the GPI process.

The results of investigations are presented, which are aimed at determining the effect of the size of SiC particles on selected properties of aluminium-based composites. As initial materials, atomized aluminium powder and silicon carbide powders of different particle size were applied. The scope of the research included the preparation of a matrix and composite material samples, as well as the determination of their selected properties. Powder metallurgy and plastic working technologies were applied to obtain the composite materials. The volume fraction of the reinforcing phase particles in the matrix was set constant at the level of 10%. All the samples were formed using the same parameters. The manufacturing process included the mixing of the components, cold compaction of the aluminium powder and mixtures as well as hot forward extrusion of the P/M compacts. Based on extrusion force measurements, it was shown that introducing smaller silicon carbide particles into the matrix resulted in the necessity to apply a higher load. For extruded materials, their relative density, hardness and abrasion resistance were determined. The results obtained from compression tests performed at room temperature and at 200°C allowed us to construct flow curves for the investigated materials. Microstructure examination was also performed. It was shown that application of the proposed forming technology results in obtaining products showing a relative density close to that of a solid material. The introduction of silicon carbide particles into the matrix caused an increase of true stresses at which deformation proceeded, regardless of the test temperature. In the case of compression of the samples performed at 200°C, the increase of stresses was observed as a result of a reduction of the reinforcing phase particles size in the matrix. In case of compression tests performed at room temperature, no unequivocal influence of particle size on the character of the obtained curves was observed. The realized microstructure examination revealed uniform distribution of SiC particles in the aluminium matrix. The particles were closely adherent to the matrix, and the metallographic specimens did not reveal any voids caused by particles falling out during specimen preparation. The comparative abrasion test showed that the introduction of 10% SiC particles into the matrix and increasing their size, with their volume fraction held constant, leads to lower abrasive wear of the investigated materials. Based on the obtained results, it was concluded that in the case of the given components and their forming technology, the introduction of particles into the matrix has a favourable effect, while their size influences individual properties differently. Therefore, the final selection of the proper size of silicon carbide particles applied as reinforcement in the aluminium matrix, should be based on the knowledge of the characteristic and working conditions of the composite product, as well as the expectations to be met.

The objective of the research work was to evaluate the possibility of forming high quality composites based on the Al17Si5Fe3Cu1.1Mg0.6Zr alloy, reinforced with silicon carbide particles, by means of preliminary hot compaction and hot extrusion processes. The mixtures were prepared with a matrix alloy powder and reinforcing phase, with a volume fraction of SiC particles maintained at 5, 10 and 15%. The feedstock to be extruded was prepared by preliminary hot compaction of the powders and composite mixtures. Subsequently, the semi-finished products were subjected to forward extrusion in isothermal conditions. For the obtained materials, both after compaction and after extrusion, their relative densities and hardness were determined. For the extruded materials, their compressive strength was determined, stress-strain curves were constructed, and their microstructure was analysed as well. The obtained materials showed high relative density and mechanical properties depending on the amount of deformation and volume fraction of the reinforcing phase. As a result of introducing SiC particles into the matrix or increasing their volume fraction, an increase of hardness was observed. Hot extrusion resulted in decreased hardness as compared to the material after preliminary compaction. With a volume fraction of SiC maintained not higher than 10%, the compressive strength of the extruded materials increased, while at 15% the average compressive strength was lower when compared to the matrix alloy. Based on room temperature stress-strain curves it was found that introducing particles into the matrix or increasing their volume fraction caused a decrease of the strain level at which failure of the specimen occurred. Increasing the volume fraction of SiC particles up to 10% resulted in a strengthening of the matrix, while in the case of a composite containing 15% of particles, a lowering of strength was observed. Specimens subjected to compression at a temperature of 200°C were deformed plastically, and the stress value at which the deformation occurred increased with an increasing volume fraction of the reinforcing phase. The microstructure of the matrix obtained as a result of extrusion realized with the assumed parameters was fine-grained. In the case of composites, the observations revealed a uniform distribution of SiC particles in the matrix. Based on the obtained results of the investigations, it was concluded that in the case of products formed with the assumed parameters, the introduction of SiC particles into the matrix, with a volume fraction maintained not higher than 10%, has a favourable effect, while at 15% a decrease of the analysed material properties at room temperature and their increase at an elevated temperature is observed. The obtained results of investigations allow us to conclude that the decision to introduce SiC particles into the Al17Si5Fe3Cu1.1Mg0.6Zr alloy matrix as a reinforcing phase, as well as of their volume fraction, should depend on the foreseen working conditions of the element made of this material.

The paper presents the results of investigations on the composition of mineral components used for ceramizable silicone rubber-based composites. By using different crystalline phase additives, it is possible to assure the proper course of composite degradation and its transformation during the ceramization process. Three crystalline components were tested as an additive to silicone rubber - bentonite, kaolinite and wollastonite. They were added simultaneously with the glassy phase. These compounds during firing evolved (decomposed) and introduced into the ceramized material a polycrystalline structure, responsible for its properties. The characteristic of the ceramized composite body created during heating was investigated by mercury porosimetry. The porosity evolution was described in the range of 600÷1050°C.

Polymer composites with fibers are widely used as construction materials. Different fibers are used (eg. fiberglass). One method of forming composite materials is injection molding. The paper presents chosen results of investigations on polymer flow during the mould cavity filling phase of the injection molding process. The process is characterized by high dynamics, which causes several technological difficulties, both during injection mould design and during product implementation to the production stage. Deep understanding of the phenomena which occur during filling an injection mould may lead to a more effective design of the processing tools and shortening of the time for the implementation and production time. In the paper the theoretical basis for modeling fiber orientation in an injected polymer composite is described. The orientation and distribution of fibers have a substantial influence on the mechanical properties of a molded part. A computer simulation of the injection molding of a polypropylene composite with glass fiber (PP + 20% glass fiber, Aqualoy 125B, A Schulman NA) is conducted. Special attention is given to the results concerning the orientation of the fiber during processing. Selected results of the computer simulation of the flow velocity distribution of the composite, Poisson's coefficient and fiber orientation tensor across the molded part and selected cross-sections are presented. Significant discrepancies in the orientation of the fibers, depending on the nature of the flow of the injected composite are affirmed. These disparities affect the lack of uniformity of the mechanical strength of the molded part. The author plans to extend the scope simulation research to determine the effect of processing conditions on fiber orientation.

High-performance applications in mechanical engineering and vehicle construction increasingly have to fulfil high demands concerning passenger comfort and the conservation of natural resources. Therefore, lightweight structures made of textile-reinforced composites exhibit a considerable application potential due to their inherently wide-ranging ability for function integration and design freedom. Additionally, the use of so-called compliant elements with specifically adjustable compliances offers the possibility to transmit motions simply by means of structural deformations. For the investigation of the deformation behaviour of such composite compliant hinge mechanisms as well as for the analysis of anisotropism-related coupling effects of multilayered composites, bending free of shear force can be used advantageously. This paper makes a contribution to the efficient cyclic testing of textile-reinforced compliant structures. Thus, a novel kinematic test rig has been developed, which can be utilized for the static and dynamic bending tests of composite (strip shaped) beam specimens. The main unit is a multifunctional six-membered linkage that allows a moment's application free of shear force by providing a pure bending load. The design studies mainly focus on the mechanical adaptation of an appropriate mathematical characterized mechanism to the trajectory of the movable restraint point. Furthermore, basic test results in consideration of the moment, force, and deformation of textile-reinforced compliant hinges are shown and evaluated with the help of computer tomography.

Composite materials with their adjustable, high specific mechanical properties offer the possibility to realise load-adapted, locally functionalised lightweight structures. Here, compliant structures characterised by individually adaptable deformation behaviour are promising applications. Notwithstanding the substantial degree of function integration, competitive serial production of such components can be achieved by the use of composites based on thermoplastic matrix systems in close combination with efficient manufacturing technologies. This paper contributes to the development of composite compliant structures, specifically designed for use in bending dominated applications. The experimental studies including different fibrereinforcements make allowance for the composite adapted design of a beam structure and the associated load transfer elements. For this purpose, an adapted testing device was designed and installed, and various composite bending structures are compared. The experimental results show the suitability of fibre-reinforced composites with large elastic deformability for compliant structures. Different designs of the load transfer element were tested. Compared to the basic design, an increase of the load bearing capacity of the compliant structure by up to 100 % was achieved. This is facilitated by the aligned design of the composite beam and its associated load transfer elements.

Bone cement used in orthopaedics (PMMA) is a viscoelastic material. Macroscopically, the cement structure is composed of aggregates in the form of polymer spheres with the dimensions of 10÷18 micrometers connected with polymerized monomer bridges. After mixing, it is initially a fluid, which then becomes increasingly viscous and hardens. During polymerization, the material is plastic and can be easily moulded and it penetrates deep into the fine trabecular structure of the bone. PMMA is characterized by low impact strength, which, in cements without fillers, reaches the level of KC = 1.16÷5.2 kJ/m². This causes the material to show tendencies to crack at even a low dynamic load. A number of studies have demonstrated that PMMA tends to fragment and chip in artificial hip joints. The paper presents the investigations of the PMMA structure carried out for bone composites with implanted hip joint prostheses. The results of empirical investigations which allow for the determination of PMMA crack resistance were also presented. In order to determine crack resistance in bone cement, strength tests were carried out by means of an Inspekt Desk 20 machine manufactured by Hegewald & Peschke, equipped with a device for three-point bending. The measure of crack resistance was a critical value of the stress intensity factor KQ. In order to compare the results, numerical calculations of the stress intensity factor (WIN) were also carried out for the three-point bending of a SENB sample made of SIMPLEX P + carbon fibre.

The article presents the results of research on the modification of the properties of ceramic Al₂O₃ using particles of nickel. As starting materials, powders of Al₂O₃ and Ni were used, from which mixtures of Al₂O₃+x% vol. Ni (x = 0, 1, 3, 5) were prepared. They were subjected to sintering in an argon atmosphere at 1450°C for one hour. The physical properties of the composites such as: density, porosity, absorptivity and contractility were determined. Moreover, analyses of the received phase composites (from the surface and cross-section) have been made using the diffraction method, which showed NiAl₂O₄ spinel phase formation. Spinel is formed mainly at the border of Ni and Al₂O₃ grains. It was confirmed in the microstructure photographs taken using scanning and transmission electron microscopy methods. The mechanical properties have been investigated:hardness HV, nanohardness and fracture toughness (crack length measurement method with Vickers indentation). As the amount of nickel hardness HV decreased from 17.3 GPa to 100% Al₂O₃ to 13.2 GPa for Al₂O3 + 5%vol. Ni, the nanohadrness values increased, which could have been caused by the presence of a spinel phase. The composites were characterized by higher resistance to brittle fracture than 100% Al₂O₃. This was due to blocking, deflecting and bridging cracks in nickel and by branching cracks by spinel particles.

Ceramic-metal composites, obtained via pressure infiltration of porous ceramics Al₂O₃ by cast aluminium alloy EN AC-AlSi11 (AK11), were studied. As a result, composites of two interpenetrating phases are obtained. They are composed of 30 vol.% of ceramics. The pore sizes of the ceramic preforms varied from 150 to 500 μm. The results of the X-ray tomography proved very good infiltration of the pores by the metal. The residual porosity is approximately 9 vol. %. The obtained microstructure with percolation of the ceramic and metal phases gives the composites good mechanical properties together with the ability to absorb strain energy. Image analysis has been used to evaluate the specific surface fraction of the interphase boundaries (Sv). The presented results of the studies show the effect of the surface fraction of the interphase boundaries of ceramicmetals on the composite compressive strength, hardness and Young’s modulus. In addition, the mechanical properties depend on the degree of infiltration. Compression tests for the obtained composites were carried out, and Young’s modulus was measured by application of the DIC (Digital Image Correlation) method. Moreover, Brinell hardness tests were performed. The composites microstructure was studied using scanning electron microscopy (SEM). SEM investigations showed that the pores are almost fully filled by the aluminium alloy. The obtained results show that the infiltration method can be used to fabricate composites with percolation of the microstructure. However, the research is at its early stage and will be continued in the sphere of the characteristics of interphase boundaries.

Polymeric laminated composites show great potential in many engineering applications, especially in the aircraft industry, owing to their specific strength properties. Many machine components made of polymeric laminates are subjected to intensive vibrations. According to the viscoelastic nature of such composites, some specific effects e.g. energy dissipation could be observed during cyclic vibrations. Therefore, it is necessary to understand this behaviour and to develop appropriate methods and models for diagnostics and monitoring purposes. In this work the authors present the results of an experimental investigation into the vibration response of cyclically loaded glass-fiber reinforced polymeric (GFRP) rectangular plates. Initially, the frequency response functions (FRF) for the investigated specimens of various lengths were obtained during laboratory experiments. The natural frequencies of the specimens were determined based on their FRF. Then, the specimens were loaded on the first three natural frequencies to obtain characteristics showing the phenomenon of energy dissipation. Dynamic testing was carried out using a laser vibrometer and a piezoelectric force sensor. The evolution of the dynamic moduli was investigated based upon the measurement results, allowing estimation of the empirical model of material energy loss, necessary in building and testing the analytical model of the self-heating properties of the specimen material. The influence of an excitation frequency and the length of the specimens on their dynamic behaviour was additionally studied. The results of the conducted research could be successfully applied in diagnostics and structure health monitoring (SHM) applications and could be used to develop fatigue and fracture models of viscoelastic GFRP laminated composites.

This paper presents experimental studies on the thermal response of laminated composite plates under resonant vibrations. The thermoviscoelastic behaviour of laminated glass-fibre reinforced polymer (GFRP) composite specimens was studied. The specimens were subjected to purely flexural bending cyclic loading conditions on their three first bending resonant frequencies. During the examination of the specimens, frequency response functions (FRF) and thermal responses were evaluated. Infrared images acquired during the experiments also allowed the study of the temperature profiles of the specimens and temperature evolution over the loading time. The maximal magnitudes of temperature were observed at a point located on specimens’ clamp line, which was caused by the maximal stress magnitudes. The temperature evolution curves revealed the double-exponential characteristic which was affected by the evolution of the dynamic moduli of the material during resonant vibration. The temperature increased until the equilibrium between the dissipated energy and energy convected to the environment was reached. Based on the measurement data, the empirical model of self-heating temperature evolution was proposed. The influence of the excitation frequency and the plate length on the obtained temperature distributions was also examined. It was noticed that the excitation frequency was linearly dependent and the plate length was power dependent on the self-heating temperature, which confirms the numerical results obtained in previous theoretical studies. The obtained results could be used for the prediction and prevention of composite structural degradation during resonant cyclic constant-strain loading.

The influence of the solidification conditions on the microstructure of an Ni₃Al/C composite, i.e. an engineering material in which the role of a lubricating phase, usually performed by reinforcing phases, is played by carbon, has been studied. When proper conditions are observed, a nickel-aluminium alloy composed in 87 wt. % of nickel and in 13 wt. % of aluminium, containing moreover carbon in an amount of 2.5 wt. %, forms in the solidification process a natural Ni₃Al/C "in situ" composite. The composite matrix is nickel aluminide characterised by very interesting functional properties, particularly high strength at elevated temperatures. An inspiration to these studies was the surprisingly similar microstructure observed in different types of cast iron and in the fundamentally different, in regard to chemical composition, structure and microstructure, nickel - aluminium alloy. The aim of the present study was to evaluate the effect of the solidification conditions on the shape of the precipitates of graphite particles. The morphologies of the graphite phases were examined and their chemical composition was determined.

Temperature and time of heat treatment influence on the structural stability of Fe40Al intermetallic alloy with and without addition of alumina ceramics was investigated. Low energy milling in a ball mill was applied for material manufacturing. The batches were formed by cold-consolidation at 300 MPa pressure. Initial sintering was carried out at 1050˚C under 40 MPa of charge for 15 minutes in vacuum. The last step of Fe40Al sinters (with and without alumina nanoceramics addition, manufacturing was essential sintering). The process was carried out in tube oven with constant ambient gas flow (argon atmosphere) at 1200˚C for 1 hour. On classically prepared metallographic cross-section of samples with various additions of alumina nanoceramics, analysis of structure was carried out after initial and essential sintering. For all the technological options stereological investigations of grain size descriptions were done after full cycle of heat treatment. Material was cyclically heated at 800 and 1000˚C in air atmosphere for 150 h. Obtained results reveals that long heating of the Fe40Al intermetallic alloy based sinters leads to gradual grain growth of the matrix. Changes in grain size showed that doping with alumina nanoceramics in Fe40Al inhibits grain growth.

Fibre-reinforced composites are susceptible to damage resulting from impacts. This damage may lead to a reduction of composite strength and load-bearing abilities, both in static loading as well as during subsequent impact events. Composites with improved tolerance to ballistic impact using inexpensive, common materials i.e. E-glass fibre and unsaturated polyester resin, have been manufactured by means of modern, yet popular moulding technology. Composite materials were reinforced with an E-type glass fibre in the form of a continuous filament mat and woven roving. The fibre content in the composites was varied to evaluate the effect of the reinforcement fraction on impact tolerance. The composites were manufactured using the Resin Transfer Moulding (RTM) method. The extent of damage in glass fibre/polyester composites after non-penetrating ballistic impact has been evaluated. Samples of the manufactured laminates were subjected to impact using a compressed-air gun test assembly. The impactor was a free-flying 3-gram hardened steel sphere, and the impact velocities were up to 125 m/s. After the impact and damage evaluation, the samples were photographed in transmitted light, and the obtained images were digitally processed by software to measure the area of delamination. It was found that the damaged area is directly proportional to the impact energy. Moreover, reinforcement in the form of a continuous-filament mat compares favourably to loose woven roving; such reinforced composites have a much smaller area of delamination after impact of a given energy. The impacted samples were sectioned and imaged microscopically in low magnification. The damage in continuous-filament mat-reinforced composites is visibly less severe than in composites with fabric reinforcement.

In the course of their “life”, fibre-reinforced plastics (FRP) are subjected to impacts which can cause damage. This damage may lead to a reduction of FRP strength and static load-bearing abilities. In this contribution, new results of three-point flexural tests on glass fibre/polyester composites after non-penetrating ballistic impact are presented. Composite materials were reinforced using a continuous filament mat and a woven roving, and the fibre content varied in the range of 42÷61% wt. The materials were produced using the Resin Transfer Moulding (RTM) method. The impactor was a free-flying 3 g steel ball, and the impact velocities approached 130 m/s. After the impact and evaluation of the extent of damage, the samples were subjected to three-point bending tests under fixed conditions. Reduction in the critical load value was noticed. A novel approach to the evaluation of residual strength has been presented. This approach allows estimation of the actual load-bearing ability of damaged material without removing the undamaged parts of the sample. The said approach involves testing samples including a damaged area as well as undamaged samples. It was considered what effect complete elimination of the damaged field would have on the load-bearing ability of the sample. The load transmitted through the undamaged area surrounding the area of delamination was then subtracted. This allowed for evaluation of the percentage of residual properties in the damaged area. It was found that reinforcement in the form of a continuous-filament mat compares favourably to loose woven roving. Higher-reinforced composites after the impact test seem to lose their properties to a higher extent.

Aspiration to reduce product mass while maintaining good mechanical properties contributes to intensive development of composite materials. The main limitations in using of them are: the high cost of components and poor possibilities of recycling. The alternative for expensive mineral and organic fibres (glass, carbon, polyaramides) applied as reinforcements in composites may be plant-originated natural fibres. They come from renewable sources, have low mass density, low price and relatively high specific strength and stiffness. Composites containing natural fibres are easy to utilize in thermic recycling and - when using special sorts of resins - they may be biodegradable. The problem of composite material processing with the use of thermoset resins is to obtain good coupling between the natural fibres and liquid resin. It is one of major obstacles to applying natural fibres as composite material reinforcements. Improvement in the technological properties of natural fibres is possible to obtain by means of physical or chemical treatment of their surface. The paper presents the analysis of structural changes occuring within jute fabric after chemical treatment and the influence of the changes on fibre interaction with the liquid matrix resin. Investigations of the structural changes of treated jute yarn were conducted by the FTIR method with the use of a Bro-RAT FTS 60V spectrometer in the range of middle infrared. Preparations were made by the tablet technique with the use of potassium bromide (KBr) as a support. The following treatments of jute fabric were applied within the study: NaOH 1, 3, 5, 15% water solutions, methanol and vinylsilane. The yarn was exposed to the effect of the substances in various time periods - 0.5 to 6 hours. It was found that partial removal of hemicellulose from the fibres surface and near-surface areas due to treatment results in an increase of cellulose areal fraction giving an increase of polarity. It contributes to improvement in fibre wetting with liquid polyester resin. The hemicellulose contents on the yarn surface is a significant parameter deciding wetting conditions. FTIR spectral analysis of fabric treated with organic substances (methanol, vinylsilane) showed that improvement in wetting by polyester resin took place as a result of adsorption of chemical groups acting as adhesion promoters. For instance, after treatment with silane, Si-OH bonds (1915 cm^-1 peak) were detected which do not occur in untreated jute structures.

Determination of the influence of a dye addition and electrochemical ageing on the change of dynamic mechanical properties, investigated by the DMTA method for samples made of polyamide 6,6 composite with glass fibre was the aim of this work. Using this equipment, the dynamical properties of polyamide 6,6 composite in relation to the temperature and frequency were determined. The samples were bended with a frequency of 1 Hz and 10 Hz in a temperature range from −50 to 160°C and a heating rate of 2 K/min. A decrease of the value storage modulus for PA 6,6 with a content of 25% of glass fibre addicion after ageing was observed. A similar dependence was obtained for samples with dye addition. A similar dependence also was obtained for the frequency 1 and 10 Hz. With an increase of temperature, the storage modulus decreases. It was found, that after electrochemical ageing, the value of tanδ decreases. Investigation of the crystallinity degree using the DSC method as well as the investigation of the structure using optical microscopy have been made. The DSC investigations prove the decrease in the crystallization degree of PA 6,6/glass fibre composite for the samples with ageing and dye addition. The investigation results provide information about dyed PA 6,6/glass fibre composite behaviour after ageing, which can be useful in practice, when selecting the material for parts that will have to work in conditions of electrochemical ageing.

Ceramizable silicone composites of various origin, designated as A, B and C, which can be used for insulation jackets of electrical cables, were the subject of investigations. The rheology and processing studies of the materials were carried out with a one-screw laboratory Brabender Measuring Extruder 19/10 DW (Germany), operating with a screw rotational speed from 10 to 200 rpm. For evaluation of the rheological characteristics of the mixes, ƞ = f(ɣ_R) an oval capillary die head was used, whereas a Garvey’s head was mounted to the machine for determination of the extrusion rate, linear shrinkage and swelling of the extrudate (Barrus’ effect). Extrudability studies of the mixes were carried out according to ASTM D 2230-83. The vulcametric characteristics of the materials contained 2,4 (di)chloro benzoyl peroxide, as a curing agent, were evaluated with a Monsanto 100 (USA) vulcameter, according to ISO 3417. The mechanical properties - tensile strength (TS) and tear strength (TES) of the crosslinked composites were determined with a universal mechanical testing machine Zwick 1435 (Germany) according to ISO 37 and ISO 34 standards respectively. Despite similar rheological characteristics, mix A exhibits the best extrudability. It manifests itself by the highest extrusion rate, minimum linear shrinkage and the lowest expansion of the extrudate among the materials studied. All the mixes studied can be extruded with a wide range of screw rotational speed. The higher the rotational speed, the better the efficiency of extrusion, which meets industrial expectations. Edge defects appear on the surface of the extrudates when the rotational speed is low (below 60÷90 rpm). The mechanical properties of the composites studied meet the requirements of the cable industry: TS = 7÷9 MPa, TES = 12÷15 kN/m and E_B ≈ 300%. The composition of the mineral phase, in a glaze and silicone rubber matrix, is responsible for the differences in the extrudability of the composites studied. Composites containing small particles of milled quartz and wollastonite dominate over the one based on large particles of mica and zinc oxide, regarding the processing parameters.

The influence of the parameters of wire electrical discharge machining on the surface layer of Fe40Al based sinters with Al₂O₃ nanoceramics has been studied. The properties of the sinters surface layer were controlled by electric discharge machining roughing and finishing with 0.25 mm wire, where the operating conditions were: time of interval (t_p) and amplitude of current (I_A). On the basis of the load capacity curve, parameters describing the investigated sinters against abrasive wear were estimated. Changes in the materials microstructure in the sinters surface layer were also defined. Analysis of the sinters surface texture (ST) exhibited a slight influence of the kind of treatment (roughing, finishing). The smallest values of roughness were obtained for a current value of I_A = 40 A for 100 μs long intervals, after finishing treatment (Ra = 1.46 μm) and roughing treatment (Ra = 1.68 μm). The treatment parameters influence the condition of the treated surface. The parameters of the load capacity curve are also influenced by the discharge machining technological parameters. Final treatment improves theoretical abrasive wear (Rpk). The Rpk parameter values decrease with an IA current decrease. The best resistance to abrasive wear (Rpk = 2.4 μm) was found for sinters after finishing treatment with a 100 μs long interval (t_p) and current of I_A = 40 A. The sinters microstructure after discharge machining does not exhibit significant changes. The width of the layer exhibiting changes is just a few micrometers and is independent of the operating parameters.

This paper describes the research work to characterise the strain rate dependent on the deformation and failure behavior of glass fibre reinforced polypropylene. The experimental and theoretical analysis of the mechanical behaviour under highly dynamic loading is performed within the German DFG research project “Textile reinforced composite components for function integrating multi material design in complex lightweight applications”. The investigations are used for the development of novel material models for the strain rate dependent on material behaviour under in-plane and out-off-plane loads. Therefore, highly dynamic tensile and compression tests on textile reinforced composites with a thermoplastic matrix and woven or knitted fabric reinforcement are performed for determination of the strain rate, orientation dependent stiffness, strength characteristics, as well as for identification of the material specific failure and damage behaviour. Within the research work, novel testing methods and devices were developed, which enable a defined loading and accurate strain and damage analysis. Based on the experimental results, approaches for extended material models were developed, which include the strain rate dependent deformation behaviour on the one hand and the fracture mode specific failure behaviour on the other hand.

The magnetic properties of three grades of tungsten composites (heavy alloys): W90.3Ni7Fe1.7Co1, W90Ni4Fe2Mo4 and W93Ni5Cu2 were examined. The dependence between the magnetic field and magnetic induction (hysteresis loop) was measured at room temperature. To determine the Curie temperature, the measurements of magnetic induction versus temperature were carried out (in temperature range 180÷700 K). In order to completely describe the materials, microstructural characterization of the composites was performed in terms of the size and volume fraction of tungsten particles and the chemical composition of the matrix. In the case of the W-Ni-Cu composite no hysteresis loop was registered. The dependency between the magnetic field and magnetization was linear. Moreover the measured (mass)magnetizations was at a constant, extremely low level of 0.0006 emu/g in the examined range of temperatures (180÷700 K). The results obtained for this grade confirmed that the material in the whole temperature range was in a paramagnetic state. The results obtained for two other grades: W90.3Ni7Fe1.7Co1 and W90Ni4Fe2Mo4 showed that they were slightly magnetic. In the case of these materials, the magnetization measured for the field 27000 A/m was at the relatively low level of 700 Gs. Both materials were difficult to saturate. The character of the hysteresis loops prove that at room temperature, the materials are close to ferro/paramagnetic transition. The Curie temperature is approached from the ferromagnetic side, which is confirmed by the plots of magnetization versus temperature. The Curie temperatures for these grades were estimated as 320 and 460 K, respectively. The results confirmed that the composite with a copper addition is a paramagnetic material whereas the two other grades are partially magnetic.

Extrusion products in the form of polymeric ducts are mainly manufactured in the process of single-screw extrusion, coextrusion and extrusion with the expansion of an extrudate wall under negative pressure in movable segments. Different methods of forming the extrusion product allow one to obtain products with solid, cellular or corrugated walls. In addition, in all the mentioned extrusion processes, it is possible to apply extra technological treatments enhancing a given quality which might be significant in terms of the function to be fulfilled by the product or conditions of its use. Products obtained in this manner from the material display special, extra properties enabling their application in the latest technological solutions. At the moment, the greatest technical progress has been observed in optical communications technologies and it is in this sector that duct-shaped extrusion products have been applied most widely. They are laid in special concrete conduit installations and subsequently, innerducts of smaller dimensions or directly teletechnical, power or optotelecommunication cables are installed inside them. Considering all this, it is required that the structures of modern extrusion products have good mechanical properties. Less resistance to motion during the introduction of cables into the interior part of the extrusion product can be obtained through the manufacture of its internal wall with a proper geometrical macrostructure in the form of special slide ribs. Until present, extrusion products in the form of such ducts have been manufactured from high density polyethylene (PE-HD), however, due to the need to obtain enhanced circumferential rigidity, other alternative polymeric materials, copolymers as well as calcium carbonate (CaCO₃) or talc (Mg₃(OH)₂Si₄O₁₀) filled composites have been pursued. The article presents the patterns of changes in the rheological properties of propylene composites with different CaCO₃ content during their flow through the channel gap in the extrusion die. Numerical analysis was conducted with the use of the finite element method (FEM) in the area between the core forming the slide ribs and a cylinder-shaped external wall. The material within the core area flows through a specific number of macro depths whose shape corresponds to the shape of the slide ribs which are manufactured in the inner surface of the extrusion product. The ratio of rib height to wall thickness was 1:8. The rheological sevenparameter Cross-WLF model was used to analyze changes in the shear rate and viscosity of the material in a given section of the extrusion die. The results for the filled polypropylene composite (PP + CaCO₃) were compared to the results obtained for a PE-HD without additives or fillers in the same processing conditions.

The paper presents the production technology of ceramic-carbon composites designed for cylinder inserts of piston devices. Porous oxide ceramics with an assumpted porosity (20, 30 and 35%) obtained by the method of sintering grains of ceramic powder was used as a composite matrix. In the method, the sintering process is carried out in such a way that the ceramic powder particles form durable bonds (they sinter) in a properly prepared shaped sample but at the same time they do not form a dense polycrystalline material. The composite was obtained by introducing a glassy carbon precursor into the open pores of the ceramic and was then subjected to pyrolysis in the atmosphere of argon. As a result of the conducted technological tests, diverse contents of glassy carbon in the ceramic matrix were obtained. The influence of the open porosity of an oxide ceramic matrix upon the tribological properties of the fabricated composite sliding against a cast iron piston ring in the conditions of friction in air was examined. The material is destined for cylinder inserts in machines and piston devices e.g. combustion engines, air compressors and pneumatic servo-motors. The material was obtained in three consecutive stages i.e. ceramic samples with a given porosity were obtained by the gel casting method, saturation of the porous samples with a carbon precursor, and finally pyrolysis of carbon precursor introduced into the pores of oxide ceramics. The obtained ceramic-glassy carbon composite (CGC) features low thermal conductivity close to conductivity of oxide ceramics , a high wear resistance and friction coefficient which allows sliding in the conditions of limited lubrication. The fabricated material was subjected to tribological tests on a pin-on-disc stand sliding against a cast iron pin in the conditions of friction in air. The friction coefficient of the examined contact largely depends upon the ceramic matrix porosity. The lowest value (µ ≈ 0.3, at p = 0.8 MPa, v = 2.5 m/s, s = 5000 m) was obtained in the contact with 30% matrix porosity. The results are the basis for further investigations on optimal chemical composition and manufacturing processes in order to reach the required utility properties. Composites manufactured upon an oxide ceramic matrix with a 30% porosity feature the best tribological properties. Such properties are achieved due to a sufficient amount of glassy carbon present in the oxide ceramics pores. Glassy carbon is marked by low shear resistance and high ceramic matrix hardness therefore low values of friction forces are possible to be reached.

The composite materials of Al/SiC are increasingly used in various industrial fields such as automotive, aerospace. However, making full use of composite materials is possible when effective methods of machining these materials are known. Due to the content of hard particles, these materials are classified to the group of hard to machine materials. One of the effective method to achieve better performance indicators for making machine parts and equipment is hybrid machining, by which, using the existing way of working, improves machinability. This process is achieved by simultaneously feeding extra heat to the cutting zone, for example by using a laser beam. The work reported here focus on analysis the composite microstructures of A359/20SiCp (F3S.20S DurAlcanTM) heated by a laser beam and laser-assisted turned. During analysis of the microstructures of the composite material, the influence of the laser beam on the workpiece was determined and liquid, liquid-solid and neutral matrix zones were identified. The sample surfaces after conventional turning and laser-assisted turning were compared. From the surface layers of the composite there a zone of smaller contents of SiC particles during laser beam heating was determined. As the wedge works in the areas of liquid and liquid-solid, a reduction of the cutting forces, tool wear and the machined surface roughness is expected.

The paper presents the sintering results of Al2O3-Ti(C,N) ceramics with the additions of solid lubricant materials. Al2O3 Ti(C,N) based ceramics with solid lubricating substances were sintered by the SPS- method. In the phase known as lubricants, the following materials were used: MoS2, WS2, CaSO4, SrSO4 and MoO3 and CaO. The Al2O3-Ti(C,N) ceramics were also prepared with the addition of TiB2. The SPS-sintered materials were characterized by values of relative density from 93 to 99%. In the case of the addition of 10 and 30% TiB2, the relative density, Young's modulus and hardness HV1 were close or equal to the values of the base material. For other additions, the Young's modulus ranged from 74 to 83% and hardness from 62 to 76% of the Young’s modulus and hardness value for the base material. Regardless of the additive or its volume, the fraction of the friction coefficient was 49 to 86% of the friction coefficient value for the base material. Taking into account the value of the friction coefficient and the physical and mechanical properties, the most promising material is a ceramic with the addition of TiB2 or MoO3 with CaO.

The influence of the amount of nanofiller on the mechanical properties of composites containing glass reinforced polyester waste have been tested. The earliest studies showed that using more than 10 wt.% recyclate in polyester composites significantly decreases the compressive and flexural strengths. In this work a preparation based on the polyester resin Polimal 109-32K (product of Organica - Sarzyna Chemical Works) and the nanofiller NanoBent® ZW1 - organophilized montmorillonite (product of ZG-M “Zębiec” S.A.) has been obtained. The filler was introduced to the compositions in the amounts of 1, 2, 3 wt.% of all the components. The mechanical properties of the composites have been investigated at room temperature. It was observed that an addition of 1 or 2 wt.% nanofiller NanoBent® to composites with 10 or 12 wt.% recyclate causes a increase in the strength. Styrene diffuses into the galleries of the organoclay montmorillonite easily resulting in a decrease in the amount of styrene available for crosslinking in the medium. This decreases the chain length between the crosslink sites leading to higher strength. The addition of 2 wt.% nanofiller to the composite with 10 wt.% recyclate significantly influences the mechanical properties compared to the properties of the composite without the nanofiller. Glass reinforced polyester waste may be used in 10 wt.% to polyester composites with 2 wt.% nanofiller NanoBent® ZW1 to obtain building materials like window sills.

Metal matrix composites (MMCs) dispersion hardened with particles are a product of modern and advanced technology. The functional properties of these materials depend on the type, size and volume fraction of the particles of the reinforcing phase, on the type of matrix, and on the method of fabrication. This study describes composite materials based on nickel aluminide Ni3Al reinforced with ceramic particles of the carbides of metals such as W, Ti, Nb, Zr, and Ta, fabricated by the “in situ” SHSB method patented by the Faculty of Foundry Engineering, AGH University of Science and Technology. The most serious drawbacks of the commonly applied “ex situ” methods are microporosity, gravity segregation, and poor wettability of the particles by the liquid metal matrix. All these drawbacks can be avoided when the "in situ" method is applied. In this paper, the selected method was the “in situ” synthesis of the carbides of titanium, tungsten, zirconium, niobium and tantalum by a spontaneous exothermic reaction taking place in an Ni3Al alloy melt. The selection of the intermetallic compound Ni3Al as the composite matrix was dictated, among others, by its ability to become plastic, and by its high resistance to oxidation in a wide range of temperatures, combined with the high resistance to creep and tribological wear. The particles of TiC, WC, ZrC, NbC, and TaC were selected as the reinforcement of the composites. The techniques used in the investigation microstructures of the experimental materials included scanning microscopy and X-ray microanalysis.

The paper presents the results of studies on the development of 3 to 6 x 10(-3) m thick composite layers in iron castings. The said layers are formed by an SHS reaction that occurs between the substrates, i.e. titanium and carbon, introduced into the mould. outcome is the synthesis of TiC carbides in a liquid alloy, where the hardness of these layers is 1950 MHV and the size ranges from 2 to 10 x 10(-6) m. Within the layer, locally coagulated clusters are formed. The stoichiometric mixture of titanium and carbon powders introduced to the mould, provokes changes in the alloy solidification conditions. This was confirmed by a DTA analysis, the results of which have indicated a change in the chemical composition of the alloy and local temperature rise in the reaction zone, amounting to 85 K respective of the remaining part of the casting.

Copper-intermetallic fibrous composites were produced using the powder metallurgy method followed by extru-sion. The mixtures of Cu powder with 1 wt.% Ti; 2.5 wt.% Ti and 5 wt.% Ti powder were cold pressed and sintered at a temperature of 850oC. The sintered material was extruded using the KOBO method. During extrusion the hard particles containing copper- titanium intermetallic phases undergo a plastic deformation assuming a fibrous shape as the processed composite consists of a copper matrix reinforced with fibrous particles of copper-titanium intermetallic phases. Metallographic examinations of the composites revealed uniform distribution of the reinforcing particles in the copper matrix. SEM investigations and X-ray microprobe analysis showed that as a result of sintering intermetallic phases were synthesized at the Cu-Ti interface. The Ti-Cu reaction products were composed of intermetallic phases in the external zone (at the copper-titanium interface) and the core containing a solid solution of copper in titanium. The microhardness of the reinforcing particles was 760 HV0.65. The samples of the composites and sintered unreinforced copper were examined in a compression test, parallel and perpendicular to the extrusion direction. The yield strength value of the composites increases with an increase in the number of reinforcing particles in the copper matrix. Mechanic anisotropy was observed for the Cu-2.5wt.% Ti and Cu-5wt.% Ti composites: the yield strength was higher for the composites loaded parallel to the extrusion direction than for those loaded perpendicular. The yield strength of the Cu-2.5wt.% Ti and Cu-5wt.% Ti copper-intermetallic fibrous composites was several times higher than that of the unreinforced copper.

Composite materials have been applied in aerospace structures in recent years. Presently, the new generation of structu¬ral composite materials for advanced aircraft are Fibre Metal Laminates (FML). They are hybrid composites consisting of alternating thin layers of metal sheets and fiber-reinforced composite material. FMLs have both low density and good mechanical properties (high damage tolerance: fatigue and impact characteristics, corrosion and fire resistance). The quality control of the materials and structures in aircraft is an important issue, also for FMLs. For FML parts, a 100% non-destructive inspection for the internal quality during the manufacturing process is required. In the case of FML composites, the most relevant defects that should be detected by non-destructive testing are porosity and delaminations. In this paper, the use of non-destructive different methods for the inspection of Fibre Metal Laminates were studied. The possibility of quality control of manufactured FML by means of defect detection procedures and processes are presented and discussed.

Metal matrix composites (MMC) were produced by the force infiltration of Saffil fiber preforms with high strength AA2024, AA6061 and AA7075. The preforms with ~10 vol.% of fibers were bonded by dipping in liquid glass and heat treated at 800oC/2 hours. Next, the preforms were placed in a mould and the liquid alloy was forced into it. The composites microstructure was investigated using scanning xL30 and transmission Tecnai FEG (200 kV) electron microscopes. The tensile strength was tested with an Instron machine. The microstructure observations confirmed that after heat treatment, the Na2SiO3(H2O) binding phase turns to amorphous silica. The liquid AA2024 reacts with the silica, substituting part of the binder with a fine-crystalline mixture of MgO, Cu2Al and silicon crystallites. The AA6061also reacts with the SiO2 binder, but replaces it with a porous amorphous aluminium oxide. However, the infiltration with AA7075 left the binder mostly intact with discontinuous precipitates of MgO at the silica/matrix interface. The mechanical tests of the AA6061/Saffil were inconsistent due to a large scatter of results, but for the other composites they showed that the Saffil fibers helped to increase the tensile strength of the castings from 230 to 330 MPa and from 420 to 590 MPa for the AA2024/ Saffil and AA7075/ Saffil composites (T6 conditions) respectively.

The microstructure and properties of two types of 7475 aluminium alloy matrix composites - with additions of 10÷20 wt.% of nano-Al2O3 or AlN (<40 um) were investigated. The composites were produced through powder-metallurgy processing. Pre-alloyed 7475 aluminium powders were mixed with ceramic particles and milled in a high energy planetary Fritsch ball mill for up to 40 hours. Next, they were compacted at 380°C and 600 MPa. The microstructure of the obtained composites was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The performed investigations proved that both types of composites show a good dispersion of ceramic phases. The composite matrix was characterized by a fine grain size, i.e. less than 100 nm and contained a high density of intermetallic, Zn, Cu or Fe rich phases. The EDX chemical analysis indicated the local presence of an MgO phase at the metal/Al2O3 and metal/AlN interfaces. The microhardness of the compacts were in the range of 315÷355 HV and 250÷280 HV range for composites with micro-AlN or nano-Al2O3, respectively. It indicates that the size of the nano-crystalline matrix and intermetalic precipitates play a more important role than that of the reinforcing ceramic particles.

For the mass production of adaptive fibre-reinforced thermoplastic structures, the development of process-adapted piezoceramic modules is gaining central importance. Thermoplastic-compatible piezoceramic modules are being developed which are suitable for matrix-homogeneous adhesive-free integration of the modules in fibre-reinforced thermoplastic structures during a simultaneous welding process. The presented studies illustrate the destructive and non-destructive characterization of novel thermoplastic-compatible piezoceramic modules. Aiming at continuous improvement of module design and its manufacturing technology based on an adapted hot-pressing process, the adherence strength of the combined material partners after consolidation and suitable methods of defect detection are investigated. In addition, high voltage actuation tests under static and dynamic loading account for competitive module performance. Keywords:piezoceramic actuators, thermoplastic composites, functional integration, destructive and non-destructive testing

Due to their highly-specific mechanical properties as well as ease of design combined with economic and reproducible manufacturing processes, textile-reinforced composites based on thermoplastic matrix systems exhibit great potential for application in lightweight structures ready for mass production. Moreover, the integration of additional functional networks composed of sensors, actuators, and electric components in thermoplastic lightweight structures enables operational-dependent control and adaptation of the structural behaviour with regard to health monitoring or active vibration and noise control. For the creation of complex structures, the use of material-adapted joining techniques is necessary. This publication is a contribution to the development of material- and application-adapted rivetting technology for the joining and electrical contacting of textile-reinforced composite parts with integrated conductors. In particular, different materials and methods for the generation of conductive paths are assessed. For accurate placement of a contacting rivet, various methods for the detection and localization of the conductors after integration, are investigated. Especially X-ray technology demonstrates good performance with regard to a high volume process chain. Furthermore, the studies show the ability to use printed conductors and carbon fibres as well as conventional wires for integration in textile-reinforced composites, suitable for mass production.

The electrodeposition of the nanocrystalline Ni-Mo matrix composite containing nano-sized oxide Al2O3 has been investigated with the aim of preparing hard protective coatings. The Ni-Mo/Al2O3 composites were deposited on ferritic steel substrates in a system with a rotating disk electrode (RDE) from aqueous sulfate-citrate electrolyte solutions containing ultrafine ceramic particles in the suspension. The conditions for the electrodeposition of Ni-Mo/Al2O3 nanocomposite coatings have been developed. The effect of the most important plating parameters namely density, hydrodynamic condition and the Al2O3 concentration in the bath on the content and distribution of the co-deposited ceramic particles in the Ni-Mo matrix was considered. The structural properties, i.e. morphology, phase composition, crystallite dimension of the obtained coatings have been determined. It has been found that the content of the incorporated particles in the deposit rises with increasing applied current density, Al2O3 concentration and stirring rate (in a relatively high cathode rotation range). The rotation speed has also resulted in an increase of the molybdenum content in the Ni-Mo matrix as well as the homogeneity of the ceramic phase distribution in the whole composite volume. At the same time, a significant change in the surface morphology of the electrodeposits and a reduction of the average matrix grain size from about 40 to 10 nm has been observed.

The work presented in this article describes the use of scanning electron microscopy (SEM) with an EDS attachment in studying Early Medieval ceramic vessels from archaeological sites. These studies have allowed us to observe the shape and size of temper particles as well as analyze the chemical composition of mineral admixtures. The analyzed material consisted of fragments of Menkendorf-Szczecin type clay vessels from Polish and German archaeological sites of the 9th-11th centuries. Studies using scanning electron microscopy at various magnifications allow for the observation of mineral admixtures of different fractions, large temper particles which were added intentionally, as well as small particles which are a normal fraction of natural clay. Scanning electron microscopy studies also made it possible to classify minerals on the basis of their shapes. A group of admixtures of spherical shape and a group of polygons were identified. Point analysis of their chemical composition (SEM-EDS) allowed us to separate the minerals into groups containing quartz and those made up of other minerals containing titanium or barium in their chemical composition.

Ni+Al/Ni composite coatings on an iron substrate were successfully developed via two-step technology: conventional electrodeposition (CED) and sediment co-deposition (SCD). The Al content produced in the composite coatings was about 25 vol. %. The coating morphology and composition were characterised using light optical microscopy, scanning electron microscopy (SEM - JEOL JMS 5400) and electron probe microanalysis (EDS - ISIS 300 Oxford Instruments). No cracking, porosity or other defects were observed in the Ni+Al/Ni coating microstructure. The hardness of the Ni+Al coating was about 240 HV, whereas the hardness of the pure Ni interlayer coating was only 220 HV. The effect of heat treatment under pressure on coating phase formation was studied. The Ni+Al/Ni coatings were converted into y-Ni+y’/Ni coatings by vacuum annealing at 600oC for 2 h and subsequently at 900oC for 3 h under uniaxial pressure of 1 MPa. Full-density composite coatings were obtained. The nickel interlayer was successfully employed to block the mutual diffusion between the iron substrate and aluminium and therefore hard and brittle Fe-Al intermetallics were not formed. The hardness of the reaction-formed y-Ni+y’ layer was about 280 HV. The hardness near the surface after oxidation tests decreased to about 250 HV, which was attributed to the depletion of the y’ phase. A hardness peak of about 320 HV appeared about 15 um within the outer layer, where the alumina continuos layer was revealed. The results of the microindentation hardness measurements were in accordance with the results of the SEM and EDS analysis.

The influence of metallization process parameters such as bath composition and deposition rate on the thickness and morphology of coatings were investigated. The role of bath composition (Ni-salt, reducer, complexing-buffering additive, stabilizer, surfactants), pH value, temperature and deposition time were studied. The requirements for C-fiber/Ni-P/Al alloy composite fabrication are limited to the P-content to 2÷3 wt.% and coating thickness to less than 1 μm. The metallization process, after proper carbon fiber pretreatment, was performed in baths containing: NiSO4, NaH2PO2, glycine, stabilizers and wetting agents. The pH value was shifted to the range of 4.5÷8.5, temperature 60÷80oC and deposition time from 5 to 60 min. As a substrate for the metallization process, roving and fabrics manufactured by Tenax (3-24k filaments in bundle with 7 μm diameter), as well as mullite test samples were used. The results of the experiments, limited to changes of pH in the bath, indicated that the ratio of NiSO4/NaH2PO2 concentration is the main factor determining the P-content and Ni-P deposition time. It is the best factor for fixing the coating thickness. The increase of the Ni-P coating thickness rate also depends on the quantity of carbon fibers in the roving.

A study of the impact of Short Fibre Reinforced Polymer Composite degradation, based on a PBT matrix, on injection moulded snap geometry is reported. A nonlinear transversely isotropic material, taking into account the material ageing time, along with implemented failure criteria was used. The material direction was assigned separately for each finite element, depending on the result of the simulation of the injection moulding process. In the snap model, three parameters have been defined that could potentially affect the simulation results. These parameters have been used for the Design Of Experiments (DOE). By changing the geometric parameters mentioned above, a full set of tests was performed, which resulted in the formation of assembly forces, pulling forces and the maximum stress in the clip, served as input data for optimization. Based on a series of simulations carried out for the material in an As Received (AR) state and after material ageing, geometry optimization was carried out using the Response Surface Method (RSM). Assuming the same requirements during optimization, two different geometries were obtained, for the AR material, and for the material after ageing, which indicates the necessity to carry out similar studies already in product development in order to avoid costly and time consuming changes of serial production tools. The geometry of the latch after optimization, for the material model after ageing, ensures that the requirements for the assembly and the pull out forces needed for part destruction, posed for such components, will be met, while using the optimum geometry for the AR material does not ensure compliance with the requirements after the ageing process. The presented simulation method, taking into account the degradation of the material, enables the optimization of composite structures including the degradation of the material during the operation, which can contribute to significant savings during the design of components made of short fibres reinforced composites and the validation process.

Nowadays, structural concretes containing additives of fly-ash are quite commonly used in the construction industry. This is mainly due to economic reasons connected with the possibility of utilizing this industrial waste (fly-ash) as an effective substitute for cement. The analysis of the defects occurring inside the composite structure plays a significant role in concrete mechanics. If we know the parameters of fracture mechanics or the levels of critical compressive stresses, we can estimate at what load level a defect will develop in an uncontrolled manner in the material. The ARAMIS system is a useful tool for research on the processes of crack propagation in concrete elements. The system is designed for the optical analysis of deformations occurring in test specimens and constructional elements. Significant advantages of the system make it possible, for example, to analyse the development of initial cracks in a specimen in the course of a load application as well as to observe the propagation of cracks in a successive manner. The system provides the possibility of recording the crack propagation process in the form of a film (wmp file). The study presents the research on the fracture toughness of concretes containing 0, 20 and 30% additives of fly-ash. The composites containing a 20% additive of fly-ash were characterized by the best fracture toughness. Initial cracks propagated in the specimen at the angles from 0 to 15o. The research results demonstrate the possibilities of the practical application of the ARAMIS system for analysing the development of defects in the structure of concretes containing fly-ash additives. This system can be useful for the macroscopic estimation of crack propagation as well as for determining concrete fracture mechanics that are convergent with the results obtained with the use of traditional methods based on the estimation of press displacement.

Epoxy materials hardened with 1-ethylimidazole (1EI) or 1-butylimidazole (1BI) with (nano)silica have been investigated. The epoxy resin used was Epidian 6 (product of Chemical Works “Organika Sarzyna” in Nowa Sarzyna) and as the filler, silicas were employed: a product of the precipitation reaction from solutions of sodium silicate and ammonium salts (SiO2) and a silica modified with 3-glicydoxypropyltrimethoxysilane (SiO2-EP). The filler was introduced to the compositions in the amounts of 1.0; 2.5; 5.0 and 7.5 g per 100 g of epoxy resin and the hardener was added - 1 g per 100 g of resin. The dispergation time of the fillers was 120 minutes at 70°C. The particle sizes of the obtained powders using the laser diffraction method (Mastersizer 2000, Malvern Instruments Ltd.) were determined. The investigations of the viscosity of the epoxy composition were carried out with the use of a ARES rheometer, Rheometric Scientific: the diameter of the plates - 50 mm, the thickness between the plates - 1 mm. The curing process was determined by using differential scanning calorimetry DSC (Q-100, TA Instruments, speed rate 10 mm/min). The particle size remains in the range of 350 to 840 nm for the unmodi-fied silica SiO2 and from 450 to 950 nm for the particles modified with epoxysilane. The addition of the filler increases the viscosities of the epoxy composition from 12.74 Pa•s for Epidian 6 to the range of 14.30 to 15.40 Pa•s for the compositions with unmodified silicas and 14.50 (compositions with 1 phr of silica with epoxysilane) to 15.80 Pa•s (epoxy material with 7.5 phr SiO2-EP). The curing process enpalthies are from 490 to 590 J/g for the compositions hardened with 1-ethylimidazoleand at 281.6 to 516.0 J/g for the epoxy materials cured with 1-buthylimidazole.

Epoxy compositions and composites hardened with 1-ethylimidazole (1EI) with different silicas have been investigated. The epoxy resin used was Epidian 6 (product of Chemical Works “Organika Sarzyna” in Nowa Sarzyna) and as a filler, different silicas were applied: a product of the precipitation reaction from solutions of sodium silicate and ammonium salts and modified with 3 wt./wt. of 3-glicydoxypropyltrimethoxysilane (SiO2-EP) or 3 wt/wt./wt. of 3-aminopropyl-trimethoxysilane (SiO2-NH). The filler was introduced to the compositions in the amounts of 1.0; 2.5; 5.0 and 7.5 g per 100 g of the epoxy resin and the hardener was added - 1 g 1-ethylimidazole per 100 g of epoxy resin. The dispergation time of the fillers was 120 minutes at 70°C. The epoxy composites were hardened at a temperature of 140°C for 4 hours. The particle sizes of the obtained powders using the laser diffraction method (Mastersizer 2000, Malvern Instruments Ltd.) were determined. The investigations of the viscosity of the epoxy composition were carried out with the use of an ARES rheometer, Rheometric Scientific: the diameter of the plates - 50 mm, the thickness between the plates - 1 mm. The tensile and bending strengths were measured corresponding to standards PN-EN ISO 527-1 (speed rate 5 mm/min) and PN-EN ISO178 (speed rate 1 mm/min) by using the testing machine Instron 4206, Instron Corporation. The particle size remains in the range of 350 to 840 nm for the unmodified silica. The modified nanosilicas are in a higher particle size range of 530 to 1050 nm for the aminosilane-grafted silica and from 450 to 900 nm for the modified silica with epoxysilane. The addition of a filler increases the viscosities of the epoxy composition from 12.74 Pa•s (epoxy resin Epidain 6) to 15.78 Pa•s for a composition with 7.5 phr silica modified with epoxysilane. The epoxy composites with the nanofiller have higher tensile and bending strength than unfilled systems. The introduction of silica increased both the Young’s and elasticity modulus and additionally the tensile and bending strength of the epoxy composites.

In the paper, the results of the experimental studies on the creep characteristics of compressed concrete members strengthened with CFRP composite materials are presented. Creep consists in a process in which concrete strains in a structure are subjected to an external load over an extended period of time. Increasing strains initiate additional deformations of structures. The subsequent consequences of them are additional impacts on structural members (e. g. eccentricities). The parameter considering the influence of creep on concrete in engineering calculations is the creep coefficient that is the creep characteristic. The phenomena of concrete creep is investigated and described in specialist literature. The value of the creep characteristic can be obtained with nomograms included in PN-EN 1992-1-1:2008 Eurocode 2. In literature there is a lack of information concerning the coefficient in the case of hybrid members which are combinations of concrete and CFRP composites. The aim of the conducted investigations was to estimate the influence of transverse and longitudinal CFRP strengthening on the creep characteristic of members subjected to long-term axial compression. The experimental investigations were divided into a few stages. The studies were performed on cylindrical concrete specimens with a diameter of 113 mm and height of 350 mm. Two types of strengthening were applied in the experiment. The first type of strengthening was one, two or three layers of CFRP sheet attached around the cylindrical specimens. Second type was longitudinal seg-ments of CFRP strips (with an area AL of 378 or 252 mm2) and one, two or three layers of CFRP sheet as transverse strengthening. For comparative analyses, control unstrengthened specimens were preformed for each type of strengthening. All of the specimens were subjected to long-term axial compression in constant environmental conditions. During the investigations the longitudinal strains of the specimens were measured. When the strains stabilized the specimens were unloaded and standard compression failure tests were performed. The experimental values of the creep characteristics for each type of member was determined in the paper. The analyses of the results is presented as well.

During the operation of certain machines and equipment, like technological lines for the transportation of flue dust to landfill, mining equipment or road and agricultural machines, a specific type of intensive usage, called abrasive wear, takes place. The microcutting phenomenon of the surface layers of both partners of friction with hard particles of chemical compositions with different grain shape and properties, is another phenomenon that occurs at the time of abrasive wear. This requires the usage of hard materials, such as high-quality alloyed and carbon steel as well as heat and thermochemical treatment. The occurrence of the abrasive wear phenomenon of cooperating elements is unavoidable despite the application of the above-stated operations. The application of a chemically-hardened metal-polymer composite on the surface layer of elements, may be a good way to reduce costs, increase the durability of the used elements and simplify the method of element regeneration. When applied in the used element, the metal-polymer composite of specified composition and characteristics, which is able to create a surface layer with greater resistance to erosion, increases abrasive wear resistance in an abrasive environment. The article presents the results of the abrasive wear resistance of chemically-hardened metalpolymer regenera-tive composites and a classic steel-bearing alloy construction joint. Amine compounds with different chemical structure and reactivity (such as triethylenetetramine, poliaminoamide and a reaction product between phenol-formaldehyde and secondary amine), were adopted as cross-linking agents. These cross-linking agents made it possible to obtain composites of very different mechanical properties. Cenospheres from flue dust, electroco-rundum and silica of defined chemical and granulometric composition were adopted as abrasive material. Chemically-hardened metal-polymer composites were imposed on a steel roller, and machined to the desired size to cooperate with traditional construction materials, such as steel and bronze. The friction and wear tests were performed in conformal contact using a T-07 block-on-ring tester in the presence of the selected abrasive material. Tribological tests were conducted at a speed of 0.1 m/s and 1 MPa pressure, without the usage of any lubricant. High resistance to abrasive wear of the metal-polymer composites was proved, which means they can be used for the regeneration of machine elements that work in an abrasive environment.

Resin bonded composite magnets were prepared by tape casting using various compositions of polymeric matrix and processing variables. As a magnetic component, MQ-A M30 ribbon powder was used. The magnetic and mechanical properties versus the composite’s compositions are presented and discussed. The coercivity does not depend on the amount of MQ powder and its mean value is close to 580 kA/m. The fact that the μ0Hc does not remarkably change for various specimens means that processing the composites does not cause oxidation of the metallic component, which would lead to degradation of the properties. The remanence changes from 0.43 to 0.65 T and rises with increasing MQ powder content. The mechanical properties depend mainly on the properties of the polymeric matrix. The composite foil containing 64.72% of the magnetic component appears to present the best combination of properties. The composite magnetic films will be used as permanent magnets for applications in Magnetic Micro-Actuators and Systems (MAGMAS).

The TiN-TiB2 ceramic composite (CC) could be attractive for applications in jet engine parts, armour plates, cutting tools and dies as well as high performance electrical systems. Because of the high melting points of TiB2-TiN, consolidation of these powders requires extremely high temperatures and long duration of the sintering process for conventional sintering methods. The main causes of this problem are strong covalent bonding, a low self-diffusion coefficient and the existence of an oxygen rich surface layer on the particle surface. The compaction and sintering of nanocrystalline powders are accompanied by intensive growth of particles. The Spark Plasma Sintering (SPS) process and High Pressure-High Temperature (HP-HT) method of sintering have been applied to the formation of composites consisting of TiB2 and TiN nano- and micropowders. Commercial TiB2-TiN nanopowders, obtained using Self Propagating High Temperature Synthesis (SHS) were used for the studies. The influence of the method of sintering on the densification, grain growth, microstructure, some physical and mechanical properties of TiN-TiB2 ceramic composites were investigated. Microstructural observations revealed that both TiN and TiB2 crystal grains had micrometer sizes in the composites obtained from nanopowders for both SPS and HP-HT methods of sintering. In the materials obtained using the HP-HT method of sintering, there are numerous cracks in the compact and stresses build up during the high pressure sintering process. The TiB2-TiN material obtained utilizing the HP-HT method from nanopowders is characterized by lower porosity. In XRD experiments, TiB2, TiN and hBN phases were detected. TiB2- TiN commercial SHS nanopowders are more reactive than the mixture of TiB2 and TiN micropowders. For the composites prepared from nanopowders there is about 14% of hBN content. The amount of hBN in the composites for micropowder sintering using the SPS method is about 1.3%.

Fibre Metal Laminates (FML) are hybrid materials, consisting of alternating layers of thin metal sheets and composite layers. FML possess superior properties of both metals and fibrous composite materials. Fibre Metal Laminates are characterized by excellent damage tolerance: fatigue and impact and characteristics, low density, corrosion and fire resistance. Glare as a type of FML are composites consisting of thin aluminium layers and glass fiber reinforced epoxy composites. The most common method used to produce FML including Glare is autoclave processing (under relatively high pressure, vacuum, elevated temperature). The first large scale application of Glare laminates is the fuselage and leading edges of the vertical and horizontal tail planes of the Air-bus A-380 aircraft. Current and future research on FML is focused on generating new laminates, for example based on the combination of titanium and magnesium and carbon or glass polymer composites. In this paper, the preliminary studies concerning the manufacturing method and the properties of new generation hybrid composite materials - titanium/glass fibre reinforced laminates (Ti-G) are described. The titanium/glass composites were characterized from the standpoint of their quality (ultrasonic technique- phased array C-scan method), microstructure and selected mechanical properties (tensile strength). The hybrid Ti-G laminates were prepared by stacking alternating layers of commercially pure titanium (grade 2) and R-glass fiber/epoxy prepregs. The lay-up scheme of the Ti-G composites were 2/1 (two layers of titanium sheet and one layer of glass/epoxy prepreg as a [0,90] sequence) and 3/2. It was found that (1) manufacturing Fibre Metal Laminates including Ti-G composites using the autoclave technique is advantageous for the reason of obtaining higher quality and repeatability of the composite structures, (2) the titanium/glass fiber reinforced laminates demonstrated good bonding between the metal and composite layers and homogeneous structure without discontinuities, (3) manufactured Ti-G composites are characterized by high mechanical properties - tensile strength due to the excellent properties of both components, titanium and glass-fibre composite materials, (4) titanium/glass fiber reinforced laminates are new generation hybrid materials, which can be potentially used for composite structures in aerospace.

Epoxy-isocyanate compositions have been investigated. As components, epoxy resin Epidian 6, a product of the Chemical Works “Organika Sarzyna” in Nowa Sarzyna (Poland) and isophorone diisocyanate (IPDI) have been used. The compositions were prepared by mixing the epoxy resin with the diisocyanate in a molar ratio of epoxy group:isocyanate group 1:1 and 1:2. The accelerators were: the most often used - Girard's Reagent T (GR) as well as 1-ethylimidazole (1EI) and 1-butylimidazole (1BI). The catalyst was introduced in the amount of 0.5; 1.0 and 2.0 phr of epoxy resin. The curing process of the epoxy-isocyanate system was measured using a DSC Q-100 (TA Instruments) and an ARES Rheometer (Rheometrics Scientific). The glass transition value of the fully-hardened compositions were characterized in the second run of the DSC. The introduction of an imidazole derivate decrease of the maximum effect of the crosslinking process and the gel point of epoxy-isocyanate compositions. Increasing the accelerator content leads to an increase in the glass transition temperature of the obtained composites.

The paper presents the results of studies on the effect of combined surface and bulk modifications on the macrostructure of castings made from remelted, post-production IN-713C, IN-100 and MAR-247 waste alloys. Surface modification was carried out by applying onto the wax pattern surface, a coating containing zirconium silicate and cobalt aluminate. Bulk modification was carried out when the cast liquid alloy was passed through a special ceramic filter containing, among others, cobalt aluminate. The nanoparticles of cobalt, acting as crystallisation nuclei, are the product of a modifier reaction (CoAl2O4 inoculant) with the chemically active constituents of the nickel alloys and with the additional filter components in the form of Al and Ti powders. The filters were placed in the mould pouring basin. The beneficial effect of combined modification on the macrostructure (equiaxial crystals) and mechanical properties was stated. The effect of the active constituents present in the nickel alloys and in the filter material was confirmed. A particularly strong refining effect on the macrostructure of equiaxial crystals was obtained in the MAR-247 alloy, which contained the strongest chemically active additives of Hf, Ta and Nb. A hypothetical model of the surface and bulk modification was developed. A strong influence of the alloy pouring temperature on the modification effect was reported. Modification was most effective when the pouring temperature did not exceed 1440oC.

An important feature of injection-processed functional polymer composites is viscosity. Powder increases the viscosity of such a composite. Viscosity depends on the polymer processing properties and the shape and size of the powder particles. The injection temperature is also important. In the conducted analyses, High Impact Polystyrene (HIPS) and General Purpose Polystyrene (PS) served as the matrix for the composites. Powders with flaky and spherical particles constituted the functional phase. Powders with permanent magnetic characteristics produced from Nd-Fe-B alloys were used. In the analysis, multi-fractional (commercial) powders and selected fractions of two types of powders were used. Composites containing variable quantities of multi-fractional powders were obtained. The content of the powders was from 40 to 54% of flaky powder and up to 64% of spherical powder by volume. In addition, composites containing the selected fractions of both types of powders were prepared. The content of fractional powders was constant and it was 48% by volume. The samples were produced by injection of the composites at temperatures from 160 to 240°C. Polystyrenes and composites with a zero shear rate have the greatest viscosity. Increasing the shear rate leads to a reduction of viscosity. The viscosity of composites with flaky powder decreases at the fastest rate. For spherical powder, the viscosity reduction rate is slower and for polystyrenes - the slowest. Slightly higher viscosity values (for the same shear rates) were obtained for general purpose polystyrene and the composites in which it served as the matrix. In composites with flaky powder, the reduction in viscosity is greater if the powder content is higher. For composites with spherical powder, an increase of the shear rate results in constant reduction of their viscosity. The viscosity of composites (with a constant content of fractional powders) decreases along with an increase of the size of its particles. An attempt was also made to explain the phenomenon of the faster reduction of viscosity of composites with flaky powder compared to composites with spherical powder through proposing a model describing the emer-gence of easy-slip surface. In addition, as the temperatures of the injected composites increase, their viscosities decrease.

The main advantage of ceramic-metal composites is the increase of fracture toughness of the brittle ceramic matrix. The slip casting moulding method is widely used in the ceramic industry, which gives the possibility to obtain products of complicated shapes without green machining. Good quality and homogeneity of powder consolidation is crucial in the ceramic and ceramic matrix composite fabrication process as it influences the properties of the material. In the case of such complex systems as powder mixture dispersions in a liquid medium (slurry), it is indispensable to investigate the phenomena taking place at the solid-liquid interface which determines dispersion stability and governs the interaction characteristics between the particles of different types (ceramic and metallic). In the paper, the results concerning ceramic matrix ceramic-metal composite fabrication via the slip casting method are presented. The following materials were used: alumina powder (TM-DAR, Tamei Japan) of average particle size D50 = 0.21 µm, specific surface area of SBET = 14.5 m2/g and density of d = 3.8 g/cm3, and nickel powder (Sigma-Aldrich) of average particle size D50 = 2.17 µm, specific surface area of SBET = 2.1 m2/g and density d = 8.9 g/cm3. Ceramic and metallic powders show great differences in electrokinetic behavior, which can cause the heteroflocculation effect to take place in the suspension. In order to investigate the particles interaction character, the zeta potential of each powder and its mixture was measured. The zeta potential measurements were performed on diluted suspensions that contained deflocculants, as a function of pH. Additionally, the particle size distribution of the diluted slurries was conducted in order to investigate the agglomeration characteristics. Rheological measurements of the slurries were performed. Furthermore, the chosen physical and mechanical properties of sintered bodies were examined (i.e.: bending strength, hardness and fracture toughness)

The work is the continuation of an investigation conducted in the Polymer Institute concerning the modification of epoxy resins with the aim of utilizing these materials for production by means of Resin Transfer Moulding (RTM). In the work, the mechanical strengths and glass transition temperature were reported for epoxy-vinylester compositions/composites. The following kinds of epoxy resin were used: Epidian 6 or Ampreg 22 hardened with 1-ethylimidazole and vinylester resins; VE-2MM or Atlac 580 ACT cured with t-butyl perhydroxide. In an earlier paper, we proved that modified epoxy resin with vinylester resin causes a decrease in viscosity and makes it possible to form an Interpenetrating Polymer Network (IPN). This described modification leads to an improvement of mechanical durability, especially with a content of vinylester resin in the range of 30÷50 wt.%. The selected curing agents made it possible to obtain a Simultaneous Interpenetrating Network for the components.

In recent years, composite structures have become very popular for different applications, predominantly in the aerospace industry. Their mechanical properties provide very useful materials in aviation as a primary structure. It is well known that glass/epoxy polymer composite is characterised by its lightweight and corrosion resistance in comparison to traditional materials. The main aim is to guarantee durability and safety during the manufacturing process in the case of the possible appearance of structural defects. Porosity and delamination detection is a very important factor in solving the problem of quality. One of the basic non-destructive testing methods of detecting discontinuities in structures used in aviation is ultrasonic inspection with C-scan images. Their objective is to analyse the composite structures particularly for quality inspection in aviation. This paper presents research about the relationship between the attenuation level of an NDT technique (C-scan) and void content in glass/epoxy composites. An analysis of the microstructure and characteristics of discontinuities are presented and discussed. The observations have given the results of three distinguished types of microstructures depending on the attenuation level in ultrasonic testing. The level of void content for this specific type of composite was determined from 2% to 5% and this can be classified as a medium quality composite structure. A linear dependence was found between the attenuation level in ultrasonic inspection and the percentage of voids content in a glass fiber reinforced polymer composite. The correlation between ultrasonic inspection and the analysis of microstructure is a useful method in composite structures engineering.

In this paper the possibility of using a modern NDT technique - THz electromagnetic waves for composite ma-terials defects detection and identification was investigated. Two technological defects were investigated voids and internal delaminating. The composite materials were hand lay up made. Several kinds of reinforcing fibers (glass, basalt, jute) and polyester resin were used. Glass micro spheres and mica plates were placed at different depths in order to simulate technological defects. The specimens were tested using terahertz frequencies electromagnetic waves. The goal was to verify if the NDT method is appropriate to identify technological defects, misuse damage as well as determine parameters such as depth or size.

Composites belong those materials that are systematically developed due to the rapid technological advancements observed in recent years. These materials are successfully used in various fields just because it is possible to obtain the desired properties through adequate selection of the reinforcement and matrix, the components of a new material. It is important, however, that the distribution of the reinforcement phase be as uniform as possible, particularly in laminates, where reinforcement layers undergo saturation. If this requirement is satisfied, the composite has good quality, especially when high material strength is the desired property. In this study, two kinds of laminate composites that differ in their reinforcement type are compared. In both cases, the reinforcement was composed of glass fiber (a mat, made of roving, cut into short pieces, chaotically placed in a plane; , and a woven fabric, made of long roving, produced by interweaving bundles of fiber glass at right angle in a the plane). The matrix was epoxy resin (Epidian 5 with Z1 hardener). A series of samples was prepared, that differed in the number of reinforcement layers (3, 6, 9, 12). They were tested for bending according to the PN-EN ISO 178 standard: ‘Synthetic materials: determination of properties in bending tests’, using a testing machine H10K-T. The test results lead to a conclusion that the best bending properties are obtained for laminates with reinforcement arranged in the form of a fabric, which is due to the advantageous distribution of stresses on the long fibres of the reinforcement. Bending strength also depends on the number of reinforcement layers. In this respect, both types of material (mat, fabric) with nine layers yield the best results. The calculated values will be utilized in further research for the creation of a mathematical model describing the strength of tested laminates depending on the number of layers and type of reinforcement phase.

The study presents the results of comparative experimental testing of selected glass - polyester layered composites. The composites are symmetric, mixed (fabric - mat reinforcement), manufactured with the contact technology applied for shell segments of composite covers of engineering structures. The base composite is the laminate of a CSM300/4xWR600/CSM300 ply sequence used in the Klimzowiec sewage-treatment plant. Two research problems are considered: 1. the influence of the ply sequence in a glass - polyester composite on its load capacity, 2. the influence of the manufacturing technique of a glass - polyester composite on its load capacity. The comparative testing in problem 1 has been performed for the following laminates: the L-4F-2M laminate (matrix: Polimal 104 T polyester resin (inflammable), ply sequence: CSM300/ 4xWR600/CSM300), the L-2F-5M laminate (matrix: Polimal 104 T polyester resin, ply sequence: CSM300/WR600/ CSM450,300,450/WR600/CSM300). The comparative testing in problem 2 has been conducted for the follo-wing laminates: the L-T laminate (matrix: Polimal 104 T polyester resin, ply sequence: 3x(CSM450/WR600)/CSM450), the L-AWTP laminate (matrix: Polimal 104 AWTP polyester resin (with a styrene anti-evaporator additive), ply sequence: 3x(CSM450/WR600)/CSM450). The comparative testing of the load capacity has been limited to bending and interlaminar shear testing in problem 1 and to interlaminar shear testing in problem 2, performed according to the respective standards. In reference to problem 1, it has been pointed out that replacing the fabric core with a mat core considerably increases the strength to bending and the conventional strength to interlaminar shear. In reference to problem 2, it has been shown that adding a styrene anti-evaporator slightly decreases the conventional strength to interlaminar shear. Keywords:layered composite, glass-polyester composite, laminate’s core modification, styrene’s anti-evaporator influence, experimental testing

The paper presents the method of Direct Coagulation Casting (DCC) which is a recently developed method of near-net-shaping of ceramic components at low costs. The process relies on electrostatic stabilized ceramic su-spensions and their destabilization owing to time delayed in situ reactions. In the method, the enzyme-catalized reaction is used to shift the pH of the ceramic suspension to the isoelectric point, which causes coagulation of the slurry. The aim of this work is the research on shaping alumina-mullite composites with the application of a lipase-catalyzed decomposition of glycerin triacetate. Zeta potential measurements in relation to pH were performed and the appropriate substrate and enzyme was chosen to conduct controlled coagulation of ceramic slurry. In the DCC method, the optimal composition of ceramic suspension was experimentally chosen. The slip gaining a high concentration of ceramic powders, small amount of organic additives, good flow properties and the shortest time after which the intensive increase of viscosity, was considered as optimal. The paper also presents the results of the viscosity of slurries with different concentrations of dispersant and lipase. The sintering temperature leading to the best density and mechanical strength parameters was found to be 1600°C. The relative densities of DCC sintered samples were higher than 95%. The Vickers hardness and fracture toughness KIC for DCC sintered samples were measured. The main conclusion is that the DCC method, using the lipaze-catalyzed decomposition of glycerin triacetate, can be successfully applied to the formation of complex-shaped alumina-mullite composites. Very good mechanical properties can be achieved due to the low content of binders and other additives. Keywords:Al2O3-mullite composites, direct coagulation casting, enzymatic reaction, lipase, Vicker’s hard-ness, fracture toughness

An attempt to assess the possibility of adaptive techniques to estimate the beneficial and economic parameters of the forming process of composite particles in the system aluminum alloy-ceramic particles was carried out. As the input parameters for the computer analysis, the results of measurements of tensile strength of composite plastic samples in the warp of aluminium reinforced with ceramic fibres were used. Samples with different vo-lume share of fibres were made using powder metallurgy technology and the forming processing. Blending pro-cess, pressing of powder and mixtures at room temperature, and hot extrusion of compacts realized in isother-mal conditions for this purpose were used. Extrusion was carried out at different values of extrusion ratio and temperature. Results of studies on the effects of chemical composition, temperature and extrusion ratio on tensi-le strength of materials were used as the database to carry out the test analysis, using statistical and artificial in-telligence methods. Dependence of Rm on the share volume of fibers was estimated using curvilinear regression and adaptive neurofuzzy inference system ANFIS. This approach arose from the fact that in modern control sys-tems to better examine the methods based on neural networks, due to the higher speed operation and flexibility. Therefore it was assumed that the proposed comparison will give information about the possibility of their use in place of classical solutions. Based on the results of the analysis, authors concluded that the data obtained from tests of tensile strength measurements, witch amount was 72, were proved to be sufficient to carry out a test analysis using adaptive neurofuzzy inference system. It has been found highly compatibility of results obta-ined based on the proposed ANFIS method, with the results of the classical statistical ana¬lysis, carried out using the regression curves, which confirms the usefulness of this solution for computer aided design of composite materials. Based on a test analysis using the adaptive neurofuzzy system, the Rm parameter achieves the highest values when the participation of fibres in composite were between 4.0 and 5.5% by volume. The results obtain-ed confirm the adaptive techniques allow for automated correction of predefined relationship between the input parameters such as time and speed of mixing, the mixture composition, extrusion temperature, and output such as strength or density of the sample after the bench press.

Simulated calculations of volumetric shrinkage and deformation of samples SENB for PA6 and its composite with percentage of 25% of glass fiber type E were presented in this development. Simulation of injection process was carried out with help of specialist computer program MOLDFLOW PLASTICS INSIGHT version 4.1, but the three-dimensional model of moulded piece was made in the module MASTER Modeler from software package of computer program I-DEAS NX. For computer simulation the rheological model of Cross was used. For simulation of pressure phase and for defining of volumetric shrinkage and deformation of samples SENB knowledge of dependence p-v-T. In numerical calculations the equations of Tait was used. Curves of p-v-T were obtained from experimental researches made in a frame of own ground. Carrying out of simulation of injection process require data input concerning geometrical parameters of moulded piece, properties of processed plastic, conditions of injection process and data referring to injection machine into calculating program. Simulating researches were carried out on a base of made up the program of researches. The program was developed using the software package Statistica 6.0. Variation of the four conditions of injection process: pressure, pressing down, temperature of injection, speed of injection and mould temperature, was taken into consideration. The simulation was carried out for extreme parameters of injection process from arrangement 9 up to arrangement 17. In result of carried out computer simulations, extensive research material was obtained, which was subjected into detailed analysis in order to its adequate interpretation. It was necessary to present only selected results of simulating researches of injection process in graphical form.

Demand for new materials used in medicine is constantly on the increase. An essential task of material engineering is to satisfy material needs in medicine applications. A number of patients are susceptible to allergies to the used biomaterials or some of their components. Main cause of appearance of these pathologic phenomena is metals and the alloys used in prosthesis. Due to this fact, scientists, doctors and technicians have made a variety of attempts to develop modern materials which would include all biological aspects. Another goal imposed on modern technologies is to provide individual matching of implantation materials with particular applications, as some cases require enhanced mechanical properties while the others call for structure or phase composition. Long-lasting implants (joint prostheses, dental implants), typically made of metals and their alloys, are characterized by improved mechanical properties but low corrosion resistance and biocompatibility. Thus, the attempts should be made to develop materials with enhanced functional properties for application in medicine. One of the methods to obtain these materials is to develop composite-based implants that combine good mechanical properties of metallic material with biotolerance of ceramic materials. During the investigations, combined metallic and ceramic composites 316L+HAp were prepared using powder metallurgy and HP-HT method (High Pressure - High Temperature), with different percentage of addition of ceramic phase. The investigations were focused on testing of microstructure, mechanical properties and corro-sion resistance of the obtained composites in Ringer’s solution.