Fatigue life prediction of symmetric cross ply laminated composite using a developed continuum damage mechanics based model

Composite materials behavior is complicated more than metallic material because of different mechanisms of damage، damage growth rate and effect of them in each other. In this paper، a continuum damage mechanic based model is proposed to predict the fatigue life of symmetric cross ply laminated composites under fatigue loading. According to fiber and matrix elastic properties، Elastic material constants of lamina are defined base on micromechanical approach. Two damage variable of matrix and fiber direction are considered to explain stiffness degradation on the scale of the plies، which thus makes it possible to use in any stacking sequences of cross ply laminated composites. Also، it is capable to predicted fatigue life and residual stiffness of laminates under different states of stress and stress ratio. The available tension-tension fatigue tests on 0◦ and 90◦ unidirectional laminates are used to identify material parameters of damage evolution equations in matrix and fiber direction. Finally، the stiffness degradation and final failure cycle of laminates during the fatigue loading on unidirectional plies and cross-ply layups are compared with available experiments. The obtained results are show a good agreement with the experiments.