COMPOSITES THEORY AND PRACTICE

The range of materials suitable for rotational molding is not as wide as for other polymer processing technologies. An option to reduce the carbon footprint of such materials is to introduce natural fibers, such as abaca. In this work, different loadings of abaca fibers (5 to 20 % by weight) were molded using one, two and three-layer constructions. A comparison of the mechanical behavior (tensile, flexural, and impact properties) with the fiber content, considering the method of obtaining the composite (1, 2 or 3 layers) was performed. The thermomechanical behavior of the matrix was not affected due to the introduction of the fibers; apart from a reduction in the storage modulus, especially at low temperature, the curves have a similar profile. In general terms, the tensile and flexural strength were not affected by the incorporation of the fibers, that is, the composites exhibit  similar behavior to neat polyethylene. Significant improvements in the tensile modulus were obtained for the parts manufactured with 2 layers, with 10 wt% fiber in the internal one. As expected, the impact strength was reduced for all the composites, although the layer of PE on the inner side that coats the fibers counteracts this reduction to a certain extent. An increase in the heating time was observed for all the composites made in different layers; although the incorporation of fibers slightly modifies the course of the curve, the heating time is only significantly increased for loadings over 10 %. The higher energy consumption needed to obtain the part in the different layers would only then be justified by an increase in the composite properties, which is not the case of the parts obtained in this work.

The recycling processes for CFRP waste are difficult due to their complex, and multi-material composition. Consequently, there is a need for new solutions to address this issue. The focus of CFRP composite recycling processes is primarily on recovering costly carbon fibers, which are characterized by exceptional mechanical properties. Pyrolysis has been identified as an effective method for the recovery of carbon fibers without significant damage. In this study, recovered carbon fibers (rCF) were used to produce polymer concrete. The fabricated polymer concretes contained carbon fibers of varying lengths (10, 20, and 30 mm) and volume fractions of 1% and 3%. The results showed that the addition of 3% post-pyrolytic carbon fibers resulted in significant improvement in the mechanical properties of the polymer concrete. Specifically, the flexural strength increased by more than 100% compared to the polymer concrete without carbon fibers, while the compressive strength improved by more than 60%. Overall, the study demonstrates that incorporating post-pyrolytic carbon fibers in the production of polymer concretes offers a promising solution to the challenge of CFRP waste. The use of these fibers not only helps in the recovery of valuable resources but also results in significant improvement in the mechanical strength of the final product.

The demand for environment-friendly ceramic reinforced polymer matrix composite (CRPMC) fabrication leads to the development of lead-free CRPMC. Calcium copper titanate (CCTO) and barium titanate (BT) are two of the most widely used lead-free ceramics for embedded capacitor applications. In the present study, the mechanical and morphological properties of both single and hybrid ceramic (CCTO and BT) filled epoxy composites were evaluated and compared with the unfilled pure epoxy resin. Hand lay-up followed by the compression molding technique were used to synthesize the CRPMC samples. Among the single filler CRPMCs, the BT/epoxy composite exhibited better mechanical properties and density values than the CCTO/epoxy composite. The 60:40 ratio hybrid CCTO-BT/epoxy composite possessed the highest mechanical properties and density values in contrast to the other composite specimens. The SEM micrographs of the fractured surfaces of the BT and CCTO CRPMC specimens were found to have a rougher and wavier appearance than the unfilled epoxy.

For the purpose of predicting how textile preforms affect the quality of the composite material and its performance, the stitched textile preform must be characterized. Experimental compaction analysis and finite element analysis of textile preforms are the main subjects of this paper. The formability parameters of a preform can be changed by the stitching process, according to research on the mechanical properties of preforms conducted during compression testing. The load-deformation response, which is depicted in detail, had the greatest influence on preform deformation. Less fiber bundle undulation in the plane direction and more stitching thread undulation in the thickness direction were observed during compression of the stitched preform, whereas the stitching thread improved the resistance of the preform to compression loading.

Ethiopia has abundant invasive aquatic plants like water hyacinth and water lily. Large masses of these invasive plants have a negative impact on the country’s water bodies, specifically at Lake Tana in Ethiopia, by infesting and deteriorating water quality and reducing the quantity of water.  In this research work, an attempt was made to fabricate a natural fiber reinforced composite in which water lily fiber was used as the reinforcing material in a polyester resin matrix. Chopped water lily fiber reinforced polyester resin composites were prepared by varying the fiber content - 20, 40 and 60 wt%. Mechanical properties such as tensile strength and flexural strength were tested as per ASTM standards to evaluate the influence of the fiber contents. The experimental results show that an increase in the fiber content enhanced the mechanical properties of the water lily fiber reinforced polyester composite. It was found that the composite with 40 wt% fiber exhibited superior strength which could be suitably used for different applications.

Aluminium alloys have good mechanical and physical properties and are lightweight, easy to cast, and simple to machine. Aluminium alloys are widely used in the aviation industry, auto sector, defence sector, and structural industries because of their promising abilities. The fundamental aim of this study was to investigate the mechanical properties and physical characteristics of a stir cast hybrid aluminium nanocomposite reinforced with 1-3 wt.% cerium oxide (CeO2) and graphene nanoplatelets (GNPs). Utilizing SEM, microstructural analysis was carried out. The existence of the elements of the reinforcement in the manufactured nanocomposite specimens was verified using EDAX. With an increase in the reinforcement wt.%, improvements in the mechanical and physical properties were seen. In the hybrid nanocomposites reinforced with 3 wt.% GNPs and 3 wt.% CeO2, a low porosity of 1.06% was observed. The best results for tensile strength, yield strength, and microhardness were 398 MPa, 247 MPa, and 119.6 HV, respectively. The SEM micrographs of the studied materials showed that the reinforcement particles were uniformly dispersed and refined into ultrafine grains.