Statistical fatigue life prediction of cross-ply composite laminates

Within the framework of statistical models of residual strength and fatigue life established in previous work, a new model for determining the stress redistribution function is proposed to predict fatigue life of cross-ply laminates in terms of the principal fatigue mechanisms, i.e., progressive matrix cracking in 90° plies. The simple shear-lag analysis is applied to describe the cycle-number-dependent stress redistribution process and the stiffness reduction of laminates resulting from the progressive matrix cracking in transverse plies. From the strength degradation behaviour and the static strength distribution of 0° plies as well as the fatigue behaviour of 90° plies, the fatigue life of cross-ply laminates with various lay-ups can be calculated from the model. Predictions of fatigue life from the model are compared with experimental data for [0/90₂]_s, [0₂/90₂]_s and [0/90₄]_s graphite/epoxy cross-ply laminates, and good agreement indicates success of the approach.