Mixed-mode translaminar fracture of CFRP: Failure analysis and fractography

The translaminar fracture behaviour of an IM7/8552 carbon/epoxy material system was investigated under mixed mode loading conditions of GII/Gtotal = 0.12, 0.24, 0.46 and 1.00. Fracture tests were performed on cross-ply specimens using a modified compact tension configuration and a specially developed fixture. SEM of the fracture surfaces of failed specimens revealed damage mechanisms specifically caused by the introduction of a mode II component that accompanied a significant increase in the damage zone size. In order to quantify the effect that these mechanisms had on the energy dissipation process, R-curves were generated which suggested that the specimen configuration used here is appropriate for characterising fracture toughness at low proportions of mode II.