A strain-based residual strength model of carbon fibre/epoxy composites based on CAI and fatigue residual strength concepts

This paper addresses the static, compressive after impact (CAI) and fatigue properties and the failure mechanisms of T300/QY8911 carbon fibre reinforced composite laminates with different lay-ups to optimize the stacking sequence. Ten different lay-ups have been studied and the results for static strength, CAI and fatigue residual strength under different fatigue stress amplitudes are evaluated and compared with each other. The results of this study provide an insight into fatigue damage development in composites and constitute a fundamental basis for the development of a strain-based residual strength model. A new formulation is presented for a fatigue-driven residual strength surface based on controlling fatigue strain. The parameter determination formulae of the residual strength surface are established to deal with the test data effectively and easily. Finally, the model is applied to experimental data, demonstrating the practical and effective use of the proposed model. It is shown that fatigue-driven residual strength can be obtained realistically from experimental data using the new formulae.