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 resin was modified by using a thermoplastic PEI and cured with dicyanamine (Dicy). The modified resin was reinforced with cross-woven and unidirectional (UD) carbon fiber. The delamination toughness and impact tests were carried out by using a Double Cantilever Beam (DCB) testing procedure and Dynatup 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 was attributed to phase separation that occurred more easily in the cross-woven CFRP composite as a result of more space between the prepreg plies. The effect of PEI on impact energy is insignificant below 20 wt pct. Thus, the total energy absorbed was improved when the PEI content was 30 wt pct. 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 that the damage tolerance of the PEI-modified CFRP was superior to that of the unmodified CFRP. (Author)