A failure mechanism-based approach for design of composite laminates

Abstract

Composite laminates are generally designed using a failure criteria, based on a set of standard experimental strength values. Failure of composite laminates involves different failure mechanisms depending upon the stress state. Hence, different failure mechanisms become dominant at different points on the failure envelope. Use of a single failure criterion, as is normally done in designing laminates, is unlikely to be satisfactory for all combinations of stresses. As an alternate, use of a simple failure criterion to identify the dominant failure mechanism and the designing of the laminate using appropriate failure mechanism-based criteria is suggested in this paper. A rectangular panel subjected to boundary displacements is used as an example to illustrate this concept. Comparison of results using standard failure criteria such as Maximum Stress, Maximum Strain, Tsai-Wu indicates substantial differences in predicting the first ply failure. Results for Failure Load Factors, based on the failure mechanism-based approach are included. It is indicated that the failure mechanism-based design approach offers a reliable way of assessing critically stressed regions to eliminate the uncertainties associated with the failure criteria.