Abstract
This work presents a systematic study of the fatigue behavior and microscopic analysis of Carbon/Epoxy [0/45/90/-45]2S quasi-isotropic composite laminates. The failure mechanism and fatigue effects of the composites under pretorsional twist angle, low-energy impact and/or hygrothermal treatment are investigated in this study. The couple effects of the laminates under pretorsional twist angle, low-energy impact and/or hygrothermally treated as well as the distribution of the residual tensile strength and the S-N curve under various stress levels are also studied. The residual strength of the specimen under hygrothermal treatment is decreased, especially for 60oC with 60%RH treatment. Pretorsion then low-energy impact and then hygrothermal treatment specimen has the longest fatigue life, pretorsion then hygrothermally treated and then low-energy impact specimen has the secondary fatigue life that longer than the low-energy impact then pretorsion and then hygrothermally treated specimen, however, the low-energy impact first then hygrothermally treated and then pretorsion specimen has the shortest fatigue life.