Damage mechanisms induced by cyclic ply-stresses in carbon–epoxy laminates: Environmental effects

This paper aims to identify and to describe the damage mechanisms of CFRP composite laminates subjected to thermal cycling. Thermal cycling tests are performed in different atmospheres, more or less oxidative (air or oxygen) or neutral (nitrogen). Microscopic observations and weight measurements of cross-ply laminates samples, put in light a significant oxidation of the matrix when tests are carried out in oxidative environment. In such thermal loading, there exists a coupling between two degradation processes: oxidation and fatigue, which dramatically accelerates the damage build-up. In a second part of this paper, the results of some iso- and cyclic-thermal tests, on virgin or damaged specimens, are analysed in order to emphasise the coupling between the degradation mechanisms.