Failure in Unidirectional Composites with Nonuniform Fiber Distribution Under Combined Transverse Tension and Axial Shear

Abstract

This study is continuation of the authors’ previous work on examining early failure events in unidirectional polymer matrix composites under transverse tension or under axial shear. This paper considers the combined effect of applying these two loading modes. The early failure events consist of brittle cavitation or yielding depending on the local stress states resulting from the applied loading. The criterion for brittle cavitation is attainment of the critical dilatational energy density when the stress state is hydrostatic tension (or nearly so), while that for initiation of yielding is attainment of the critical distortional energy density. As in the previous works, the nonuniform fiber distribution is described in terms of the degree of nonuniformity, which is implemented in a representative volume element (RVE). Several realizations of the RVE for different fiber volume fractions and different degrees of nonuniformity are analyzed using a finite element model. The results show that the occurrence of brittle cavitation versus yielding depends on the biaxiality ratio, i.e., the ratio of the axial shear stress to the transverse tension