Energy methods for modelling damage in laminates

Abstract

The paper represents the author’s contribution to the Third World-Wide Failure Exercise, which is aimed at benchmarking current models of damage, matrix cracking, initiation of delamination and their interaction with fibre failure. The approach used for the development of damage in laminates is based on an energy methodology that requires knowledge of the dependence of thermo-elastic constants on damage. The various models, developed by the author, are applied to the majority of the Third World-Wide Failure Exercise Test Cases, which included thin and thick cross ply and quasi-isotropic laminates, loading and unloading of an angle ply laminate, bending of a general laminate, and cracking under thermal loadings. Methods used to predict ply properties from those of the fibres and matrix are also described. Crack density in the 90 degree plies was modelled using a ply refinement technique. Detailed discussion is made on a number of relevant issues (initiating defect size and shape, fibre strength, ply saturation, off-axis ply cracking, delamination, mixed mode ply cracking) and their likely effects on design.