Microstructural and Mechanical Aspects of Carbon/Epoxy Composites at Liquid Nitrogen Temperature

Abstract

Woven carbon fibers of 50, 55, 60 weight percentage were reinforced with epoxy matrix to prepare the laminated composites. These were exposed to liquid nitrogen temperature and mechanical tests were carried out at a range of 2 to 500 mm/min crosshead speeds. The main emphasis of the investigation was to evaluate the role of percentage matrix phase and interfacial areas on tensile and interlaminar shear failure mechanism of carbon/epoxy composites at cryogenic temperature for different loading rates. The mechanical performance of the laminated composites at cryogenic temperature compared with room temperature property. The woven carbon/epoxy laminates were found to be loading rate sensitive. An improvement in tensile strength and reduction in ILSS was reported after cryogenic conditioning of the carbon/epoxy laminates. Microstructral analysis was done to show low temperature damage mechanisms. The phenomenon may be attributed to cryogenic hardening, matrix crackings, carbon fiber and epoxy (matrix) contraction, anisotropic nature of carbon fibers and stress relaxation after cryogenic conditioning.