Abstract: Low-speed impact and post-impact compression test (CAI) were performed on 9A12 epoxy resin based T700 composite (CFRP) laminates at different pre-damage temperatures (180 ℃, 210 ℃, 240 ℃) and damage times (24 h, 72 h, 120 h, 168 h). Digital image technology (DIC) and micro-morphology were used to study the variation of weight loss and residual strength of CFRP laminates with damage temperature and damage time due to high temperature pre-damage. The results show that the relative weight loss rate and the decrease rate of compressive strength after impact of CFRP laminates at different temperatures are firstly fast and gradually slow, and finally tend to be stable. The relative weight loss and residual strength after pre-damage at 180 ℃ changed little with the damage time, and tended to be stable after 120 h of damage. When the temperature rises to 210 ℃ and 240 ℃, the residual strength of the laminate decreases rapidly at the initial stage of damage. After 40 h, the residual strength decreases by 20.4% and 25.1%, respectively, which is lower than that after 120 h of damage at 180 ℃. Based on the analysis of results, a linear relationship model of the weight loss caused by high temperature pre-damage of CFRP laminates and the residual strength after impact is established. The strain evolution law of the CFRP laminate in the compression direction was recorded by DIC technology, and the strain cloud map was obtained. Observing the microstructure, it was found that the high temperature damage reduced the encapsulation of the resin to the fiber, and scattered resin particles appeared between the layers. At 240 ℃, the damage form of the material changed from structural fracture to damage caused by oxidative decomposition of epoxy resin.

Key words: carbon fiber composites, high temperature pre-damage, CAI residual strength, digital image correlation technology