PREDICTION OF FATIGUE LIFE FOR MATRIX-DOMINATED COMPOSITE LAMINATES

Fatigue life for matrix-dominated composite laminates under constant amplitude tensile fatigue loading can be theoretically predicted on the basis of a fatigue modulus degradation model along with an appropriate failure criterion. The fatigue modulus degradation model used in this study takes account of the effects of a non-linear stress/strain relationship and plastic deformation which are significant for matrix-dominated composites under fatigue loading. The failure criterion used herein states that a laminated specimen fails when its fatigue modulus falls by a certain amount. From the fatigue modulus degradation model and the failure criterion, an analytical model for the statistical distribution of fatigue lives for matrix-dominated composites is derived. Experiments were also conducted on [+/-45]2s graphite/epoxy laminates to verify the theoretical model. Correlations between the analytical predictions and experimental results are shown to be reasonable.