INTERLAMINAR FRACTURE-TOUGHNESS OF CARBON-FIBER EPOXY COMPOSITES USING SHORT KEVLAR FIBER AND OR NYLON-6 POWDER REINFORCEMENT/

Mode I (G(IC)) and Mode II (G(IIC)) interlaminar fracture toughness of carbon-fiber/epoxy composites have been investigated as a function of the amount of short Kevlar-29 fiber (SKF) an Nylon-6 powder (N6P) bet ween continuous fiber layers. G(IIC) increased with increasing crack l ength as a consequence of the presence of SKFs bridging in the wake of propagating crack. G(IIC) of SKF alone could reach the maximum at an intermediate amount of SKF. G(IIC) of SKF and N6P was lower than that of SKF alone because N6P prevented the orientation of SKF to out-of-pl ane. The extent of SKF's bridging phenomenon may be influenced by the amount and orientation of SKF. G(IC) showed no significant effect with SKF and uniform irrespective of crack length. Scanning electron micro scopy after G(IIC) test showed that new surfaces were created by exten sive fiber bridging, pull-out and fracture of SKF in random direction without any fixed pattern. (C) 1997 by John Wiley & Sons, Ltd.