Stochastic damage evolution modeling in laminates

A stochastic mesomechanics model has been developed for damage accumulation analysis in advanced laminated composites. The model is based on a theory of excursions of random process beyond the bounds. Stochastic strains in the laminate subjected to random Gaussian in-plane loading are calculated using lamination theory and random functions theory. Probabilistic variation of stiffness and strength characteristics of plies is used in the analysis. A stochastic version of the maximum strain failure criterion is applied for damage probability calculation. A mesovolume concept is utilized in modeling stiffness degradation. The capabilities of the model are illustrated by predictions of damage accumulation and failure in a Kevlar (R)/epoxy [0/+/-30/90](s) laminate under quasistationary, long-term. stationary, and cyclic loading. Effects of loading rate, deviation, stationary level, and cyclic amplitude on damage evolution are discussed. Inversion of the influence of loading deviation on laminate strength with varying loading rate is revealed and interpreted. High-cycle fatigue behavior of the laminate is calculated utilizing the observed stages in failure accumulation under cyclic loading.