A Comparative Study of Failure Envelopes in Composite Laminates

Abstract

On the basis of a recent survey conducted by AIAA composite structures subcom mittee, the failure criteria used by more than ninety percent design engineers have been considered in this study. These failure criteria are maximum stress, maximum strain and quadratic polynomial (Tsai Wu, Chamis, Hoffman and Hill) failure criteria. Failure envelopes for all these failure criteria are drawn for (0/90/±45)s laminate made of T300/5208 graphite epoxy material in stress space. For the first ply failure strength, we observe a great deal of difference in the predictions made by these failure criteria. Depending upon the failure criteria being compared, the maximum percentage dif ference ranges to 75%. Because of the criticality of failure criteria in structural design, for a better confidence in the predicted strength, it is necessary to undertake further theoretical and experimental studies in failure criteria. Computer aided optimum designs may not be optimum if the correct failure criteria is not considered.