Progressive damage and residual strength of open-hole thin-ply CFRP laminates under tensile fatigue loading

Abstract

Thin-ply composites are promising structural materials because of their excellent damage resistance and fatigue properties, as well as the advantage of improved design freedom in composite structures. In this study, open-hole tensile fatigue tests were performed on carbon-fiber-reinforced polymer laminates using thin-ply prepregs to investigate the effects of varying ply thickness. Fatigue tests were performed on three types of quasi-isotropic laminates with different ply thicknesses (thin-ply, intermediate-ply, and thick-ply) at several stresses. Fatigue damage growth around a circular hole was examined by evaluating stiffness degradation and internal damage using X-ray radiography. Additionally, the fatigued specimens were subjected to static tensile tests to evaluate the effect of fatigue damage on the residual strength after fatigue tests. The thin-ply laminates can suppress fatigue damage growth and retain the residual strength properties under high-cycle fatigue at high stress level, thus validating their superiority over thick-ply laminates.