Thermo-mechanical fatigue of centrally notched and unnotched AS-4/PEEK APC-2 composite laminates

The responses of a centrally notched and unnotched AS-4/PEEK APC-2 composite laminates of two lay-ups, such as cross-ply and quasi-isotropy, subjected to tension–tension (T–T) fatigue loading at elevated temperatures were investigated empirically and systematically. The cross-ply laminate possesses the higher ultimate tensile strength, longitudinal stiffness and fatigue strength than those of the quasi-isotropic laminate at the same temperature. Notch effect decays the laminate strength seriously, but changes the stiffness irregularly. As for the rise of temperature both strength and stiffness degrade significantly. Combining both effects of notch and temperature under severe environmental condition, it is found that the cross-ply laminate possesses more resistance than that of the quasi-isotropic to cyclic loading. However, the quasi-isotropic laminate is more capable of sustaining the original strength than that of the cross-ply. Finally, a modified predictive model was proposed. It was found in good agreement with empirical data.