Interlaminar fracture toughness of unidirectional G60/913 graphite/epoxy composites

This research studies the interlaminar fracture of G60/913 graphite/epoxy composites. Experiments are conducted to measure the Mode I, Mode II and the Mixed Mode fracture toughness of this material. Fractography is conducted on the fracture specimens to study their failure mechanisms.;The measured value of the Mode I fracture toughness appears to be larger than the measured value of the mixed mode fracture toughness. This unlikely behavior is found to be that of fiber-bridging which is observed in Mode I fracture. No fiber-bridging is found in mode II and mixed mode fracture tests. The measured mixed mode fracture toughness is about 43% of mode II fracture toughness. This percentage agrees with that observed in most graphite/epoxy systems.