A general approach for the modeling of fatigue induced damage in woven fabric composites and under multi-axial stress state is outlined in this paper. Guided by isotropic hardening/softening theories of plasticity and damage mechanics, a generalized bounding surface approach is presented. It is argued that the limit surface is only a special case in such a formulation when the fatigue cycle is set to one and that under fatigue environment the limit surface contracts to a failure (residual strength) state based on the number of cycle, stress path, and stress magnitude. Within the formulation, specific kinetic relations for microcrack growth are postulated for woven fabric composites and a new direction function is specified to capture strength anisotropy of the material. Anisotropic stiffness degradations and inelastic strain propagation due to damage processes are also obtained utilizing damage mechanics formulation. The paper concludes with comparing theoretical predictions against experimental records showing a good agreement.
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