Failure Criteria for Composites

Abstract

Failure criteria for composites are the biggest single topic toward which the composites community has been engaged in extensive research initiatives and activities. Perhaps, the most notable activity in the history of composites is that carried out under what is widely known as the world-wide failure exercises (WWFE). Their aim was to independently establish the maturity of existing failure criteria and methodologies, as described and performed by their own originators, and to identify remaining challenges in accurately predicting the strength and deformation of composites. Three exercises were conducted covering more than 30 internationally recognized failure methods and those are (1) WWFE for two-dimensional (2-D) failure criteria, (2) WWFE-II for three-dimensional (3-D) failure criteria, and (3) WWFE-III for matrix cracking damage criteria. The failure criteria/methodologies have been employed by their originators. This chapter aim at piecing together a coherent set of lessons emanating from the three exercises on how the various elements of models/theories can potentially fit together to help the composites design community. Examples are provided in the form of stress–strain curves, failure envelopes, and summary tables on the limitations and the applicability of the various models. Some of the gaps identified are also listed.