Shear driven delamination propagation in two dimensions

This paper investigates, theoretically and experimentally, the propagation of delamination in shear mode II between internal ply surfaces in a laminated composite plate. By considering two special cases the problem is approximated as an axisymmetric model amenable to analytical solutions. In one case the circular crack front expands and in the other it contracts. It is shown clearly that only a (linear) fracture mechanics approach will explain the mode and threshold of failure, but that a strength-based criterion can be used to initiate propagation without the need for an initial flaw. Apart from explaining some curious phenomena, the simple axisymmetric analytical solutions may be used as benchmarks for testing the ability of finite element models to predict plate delamination when the crack front is curved (at present only simple beam models are available for the standard DCB and ENF tests, but even these tests do not really develop straight crack fronts). (C) 1997 Published by Elsevier Science Limited.