Enhanced longitudinal compressive strength of CFRP composites through matrix stiffening via flexible/rigid epoxide grafted silica: A combined analysis of simulation and experiments

Abstract

An Epoxy matrix with a high elastic modulus is designed via flexible poly (ethylene glycol) diglycidyl ether (PEGDGE)/rigid cycloaliphatic epoxy (CE) grafted silica to fabricate carbon fiber composites with a high longitudinal compressive strength by theoretical and experimental methods. The relationship between the grafting chains on the silica surface and the interphase of silica reinforced resin matrix is derived from molecular dynamic (MD) simulations and experiments. The correlations of the interphase and matrix modulus with the longitudinal compressive strength of their carbon fiber composites are investigated by combining analytic models and experimental analysis. The results show that the stretched rigid CE chain on the silica surface induces inter-penetration and interfacial reaction of the grafting chains and epoxy matrix, leading to an enlarged thickness and enhanced modulus of interphase in the silica reinforced resin matrix. According to Yasser's assumption, the modified Halpin-Tsai model and experimental verification, the enhanced modulus of the interphase resulted in a higher elastic modulus of CE grafted SiO 2 (SiO 2 -CE) reinforced resin matrix. A further contribution is that the delay of fiber buckling and decline of fiber rotation in the kinking region are attained from the higher modulus matrix, thereby providing an improvement of longitudinal compressive strength of carbon fiber composites.