Fracture toughness of PEI modified epoxy resin CFRP composites

This paper describes the delamination toughness (G(IC)) of polyetherimide ( PEI) modified epoxy resin reinforced with carbon fiber (CFRP). The epoxy re sin was modified by using a thermoplastic PEI and cured with dicyanamine (D icy). The modified resin was reinforced with cross-woven and uni-directiona l (UD) carbon fiber. The delamination toughness and impact tests were carri ed out by using a Double Cantilever Beam (DCB) testing procedure and Dynatu p impact testing machine. G(IC) of PEI modified epoxy resin CFRP composite was about 2.5 times higher than the unreinforced PEI modified epoxy resin. However, G(IC) of cross-woven CFRP was higher than that of UD-CFRP. This wa s attributed to phase separation which occurred more easily in the cross-wo ven CFRP composite as a result of more space between the prepreg plies. The effect of PEI on impact energy is insignificant below 20 wt%. Thus the tot al energy absorbed was improved when the PEI content was 30 wt%. The impact damaged area as evaluated shows the damaged area of unmodified resin to be three times higher than the PEI modified CFRP composites. This indicates t hat the damage tolerance of the PEI modified CFRP was superior to that of t he unmodified CFRP.