Development of a continuum damage model for fatigue life prediction of laminated composites

To predict the fatigue life of fibrous composites, a CDM model is proposed based on effective average local stresses such that can predict fatigue life of layered composites with an acceptable precision. Three damage variables are defined in the framework of micromechanics of a lamina to estimate stiffness degradation in fiber, matrix, and shear direction. One of the main advantages of the proposed model is that, the effects of loading in fiber direction on stiffness reduction of matrix are considered. After characterization of material parameters of the model, the model was implemented in ANSYS using USERMAT subroutine to evaluate the capability of the proposed approach under multiaxial loading. The predicted results for multidirectional composite laminates with different layups (cross-ply, angle-ply and quasi-isotropic) and also [30]16 off-axis unidirectional ply under different maximum applied loads are compared with the experimental ones. The obtained results are in a good agreement with the empirical ones for different lay-ups.