Effects of cryo-thermal cycling on interlaminar shear strength and thermal expansion coefficient of carbon fiber/graphene oxide-modified epoxy composites

Abstract

Carbon fiber reinforced polymer (CFRP) composites used in cryogenic environments have to bear cryo-thermal cycling but the effects of cryo-thermal cycling on the mechanical and physical properties of the CFRP composites have been rarely reported. Interlaminar shear strength (ILSS) and coefficient of thermal expansion (CTE) are two critical parameters for the successful applications of CFRP composites used in cryogenic environments. In this work, graphene oxide (GO) with a content range of 0.0-0.5 wt% was first introduced to modify epoxy resins in order to improve the ILSS and reduce the CTE of CF/epoxy composites. The GO-modified epoxy resins were then used as matrices to manufacture CFRP composites by a hot-press molding process. The effect of cryo-thermal cycling on the ILSS and CTE of CF/GO-modified epoxy composites were systematically investigated. It was displayed that the ILSS was enhanced by the addition of GO to epoxy resins and reached the maximum value at 0.2 wt% GO before and after cryo-thermal cycling; the CTE was also lowered to some degree by the addition of GO. Moreover, the results showed that the ILSS of the CF/modified epoxy composites was slightly increased after 50 cryo-thermal cycles while slightly decreased after 100 cryo-thermal cycles. Particularly, it was exhibited that the composite CTE was obviously influenced by the cryo-thermal cycling treatment. These results were properly interpreted in terms of fracture surfaces and interfacial thermal stresses. This work provides some valuable knowledge for guiding the usage of CFRP composites in cryogenic environments.