Mechanical Properties of a Centrally Notched APC-2 Composite Laminate Due to Fatigue Loading at Elevated Temperature (II)

The temperature versus life (T-N) curves of both centrally notched and unnotched AS-4/PEEK (APC-2) composite laminates due to constant stress amplitude tension-tension (T-T) fatigue loading were investigated systematically. The cross-ply laminate possesses the higher mechanical properties than those of the quasi-isotropic laminate at elevated temperature, and also the mechanical properties of both lay-ups are degraded significantly as the temperature increasing. Combining both effects of notch and temperature at various normalized stresses it is found the cross-ply laminate possesses more resistance to cyclic loading than that of the quasi-isotropic laminate. Additionally, the predictive strain model is in a practical and simple form. Alternatively, the T-N curves, instead of conventionally S-N curves, at variously applied stresses are accomplished for preliminary designs and applications.