Statistical model for multiaxial fatigue behavior of unidirectional plies

Abstract

A statistical model is developed for the prediction of the fatigue life of unidirectional composite laminae subjected to multiaxial fatigue loading. This model is based on the experimental data for the fatigue behavior of those laminae subjected to uniaxial fatigue loading. The method is based on the extension of the generalized residual material property degradation model previously developed to describe fatigue behavior of composite materials under a wide range of stress ratios, combined with the statistical nature of static and fatigue failure of fiber-reinforced composites. The distribution function of fatigue life is determined in terms of the distribution function of static strength of the composite laminae in different loading modes, which is considered to be stochastic in nature. The fatigue life and fatigue strength of unidirectional composite laminae under any multiaxial fatigue loading are evaluated statistically by using the fatigue behavior of the laminae under uniaxial loading in longitudinal, transverse and in-plane shear directions, which is determined experimentally through material characterization. The application of the statistical model to evaluation of fatigue life and residual strength of unidirectional composite laminae subjected to biaxial fatigue loading shows good agreement with the corresponding experimental data.