Stress and energy based prediction of crack distribution pattern in general cross-ply laminates

Abstract

Stress and energy based criteria are proposed to predict transverse crack distribution pattern in cross-ply laminates. A unit cell based variational approach is developed to derive the stress state of the unit cell of a general cross-ply laminate containing multi-cracked layers with arbitrary sequence. The accuracy of the stress state is investigated compared to FEM results. The inter- and intra-laminar interaction effects of matrix cracks are investigated and discussed. Having the stress state for all plausible crack distribution patterns, the energy release rates are derived and compared as an energy based criterion to predict the distribution pattern. The stress based criterion is implemented in a step by step procedure. Initial matrix cracks are considered to form in one transverse ply and the stress redistribution due to the presence of the cracks is used to predict the location of next crack. the stress redistribution due to presence of new cracks is then derived and the position of the next cracks are predicted. The procedure of stress redistribution and prediction of next crack positions is continued until a uniform distribution pattern is achieved in all transverse plies. Both energy and stress based procedures are described and implemented to predict the crack distribution patterns of some specific layups. The results are shown to be in agreement with experimental observations.