A Residual Stiffness—Residual Strength Coupled Model for Composite Laminate Under Fatigue Loading

Abstract

In this paper, the foregone phenomenological stiffness degradation models and strength degradation models for composite under fatigue loading were reviewed simply. A new residual stiffness model was presented and a residual strength model coupled with it was established based on the basis that they are all determined by the damage evolvement and accumulation in the multidirectional composite laminate at the same time, from which the potential relationship between the residual stiffness and the residual strength was established. The coupled model was verified by the referenced experimental data of AS4/PEEK laminates, results show that the current models can describe the stiffness degradation rule and strength degradation rule of the laminate fairly well and the coupled parameter was found to be a material constant. From the coupled relationship, the residual strength can be more accurately predicted by monitoring the residual stiffness instead of life ratio.