PHENOMENOLOGICAL ANISOTROPIC FAILURE CRITERION.

In the reported study, the failure of composites has been examined at the lamina level where heterogeneous fiber and matrix are treated as an anisotropic continuum. A phemenological framework was adopted for the formulation of a mathematical model (the failure criterion) to account for the occurrence of failure under mechanical excitations. Arbitrary failure surfaces may be readily expressed in terms of the stress or strain failure tensor polynomials which meet certain fundamental mathematical requirements. Past formulations of anisotropic failure criteria were cast in terms of tensor polynomials. Examination of past formulations and variations of different forms of the tensor polynomial reveal that the tensor polynomial encompasses maximum flexibility without redundancy. It is pointed out that rational experimental design based on the failure tensor polynomial has reduced the monumental experimental task to a limited number of guiding experiments. Experimental data for graphite-epoxy composites confirmed the viability of the experimental design. Statistical methods for data reduction employing scalar ivariants of the failure tensors were presented. Refs.