Interlaminar fracture toughness of graphite/epoxy

The fracture toughness of materials that exhibit limited yielding at a crack tip is often characterised by evaluation of the ''far-field'' J integral. However, Carlsson et al (1986) has shown that such ''far-field'' parameters may be less than ideal for composite materials where the matrix material at the crack tip undergoes extensive yielding. This paper investigates this proposition and presents the results of an experimental evaluation of the Mode II fracture behaviour of graphite/epoxy. Here attention is focussed on the effect of loading rate on the interlaminar fracture property of graphite/epoxy. The effect of the precracking procedure on the interlaminar fracture properties of graphite/epoxy is also studied.