An Improved Fatigue Failure Model for Multidirectional Fiber-reinforced Composite Laminates under any Stress Ratios of Cyclic Loading

This paper improves an existing model to predicting the fatigue life and material property degradation of arbitrarily oriented composite laminates under different stress ratios. Residual strain energy density is used to model fatigue behavior via a VUMAT subroutine in FEM package. The effects of strength and stiffness reduction are considered to obtain higher predictive accuracy than that derived with the stress-based method. Hashin failure criteria are employed to identify damage onset in the fiber, matrix, and in-plane shear of layers. Based on developed model, a sensitivity analysis is conducted to evaluate geometrical effects on the fatigue life of composite structures.