Numerical evaluation of the influence of loading rate on the interlaminar fracture of graphite/epoxy

The fracture toughness of materials that exhibit limited yielding at the crack tip is often characterized by evaluation of the `far-field' J integral. However, Carlsson et al have shown that such `far-field' parameters may be less than ideal for composite materials where the crack tip in the matrix material undergoes extensive yielding. This paper investigates this proposition and presents the results of a numerical evaluation into the use of a near-tip energy integral, the so called T* parameter, for evaluating the fracture toughness of composite materials. Here attention is focused on both the near-tip fracture parameter and on load history effects.