Investigation into mechanical properties of unidirectional carbon fiber reinforced plastics
Mirosłąw Rodzewicz*, Piotr Jaśkowski*, Anna Boczkowska**, Krzysztof J. Kurzydłowski** *Politechnika Warszawska, Instytut Techniki Lotniczej i Mechaniki Stosowanej, ul. Nowowiejska 24, 00-665 Warszawa **Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 4 No. 12, 2004 pages 414-420
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abstract The subject of the paper concerns the investigations into mechanical properties of the CFRP composite (Carbon Fiber Reinforced Plastics) of the UD-structure. Such a composite structure exists in the most loaded elements of the aircrafts, especially in the wing spar cups. It is very important for the constructor to know the relationships between the compression strength and the fibers volume fraction, obtained at the room temperature (RT) and also at the 54°C, as it is stated in the Join Airworthiness Requirements JAR-22 Gliders and Motor Gliders. It is the main subject of the presented paper. It contains such results as absolute values of compression strength (Fig. 7) and bending modulus (Fig. 10) and also the values related to the density of composite (i.e. specific compression strength - Fig. 8) or the values related to the number of roving strands in the cross-section of the specimen (i.e. fracture force for single roving strand - Fig. 9). The influence of the specimens preparation on the results of the compression strength tests is the additional subject of the work. Recently it concerns the problem of the specimens length influence on the strength tests results. It is quite obvious that the method of strength test should ensure insensitivity of the test result to the specimen length deviation (caused for example by technological process errors). The result obtained confirms, that applied method of specimen preparation is correct and ensures small deviation of the strength tests results. Apart of the strength test - another investigation was directed into microscopy analysis of the composite structure (Figs 12 and 13) using light and SEM microscope as well. Key words: composite structure, carbon-epoxy composites, mechanical properties of composites