A nonlinear constant life diagram model for out-of-plane shear fatigue life prediction of 3D woven composites

A nonlinear constant life diagram (CLD) model based on dual stress ratios (DSR) is proposed to predict the fatigue life of three-dimensional(3D) woven composites. The out-of-plane shear fatigue properties of 3D woven composites with stress ratios of 0.1 and −1 are investigated. Three fatigue life criteria are proposed to judge the critical cycle number (fatigue life). It provides guidance for determining the out-of-plane shear fatigue life of 3D woven composite under different design requirements. The concept of the S-N curve cluster is proposed to characterize the fatigue life at different typical degradation stages. Based on the S-N curve cluster, the DSR CLD model is established. It performs better than the conventional Goodman CLD model. A formula is proposed for the prediction of the out-of-plane shear fatigue life of 3D woven composites with an arbitrary stress ratio. More predicted results are provided to help other researchers to investigate the shear fatigue life of 3D woven composites deeply.