On Approximations for Strength of Random Fiber Composites

Abstract

It is shown that the combination of the gradual failure model and the rule of mixtures for modulus leads to the rule of mixtures for the strength of random fiber composite. For analysis purposes, the random composite is replaced by a laminate consisting of unidirectional plies in every direction in the plane of the laminate. When the maximum stress criterion is employed, the strength of the random composite is given in terms of the uniaxial strengths of the unidirectional composite through a simple relation. Although the method is intended for discontinuous fiber composites, it is as well applicable to some of continuous fiber composites. Other possible modes of failure are also discussed and the corresponding equations for prediction of strengths are given.