Abstract: Composite material with holes treated in wet and hot environments is used to study its change law and mechanism of impact resistance and residual compressive strength with low-speed impact testing, compression mechanics testing and digital image correlation technology (DIC). Firstly, the composite material is treated in wet/heated environment, and the degree of change is evaluated by the moisture absorption rate and weight loss rate. Secondly, a low-speed impact test was performed on the treated laminate simple, and then a compression after impact (CAI) test was performed to evaluate the residual strength. DIC information was collected for the crushing process at same time, and finally the scanning electron microscope (SEM) was used to characterize the microscopic morphology with treatments. The results show that the thermal treatments are more harmful than water-induced treatment. The difference between the strain data collected by DIC technology and strain gauge (SG) is relatively small, and the dispersion of DIC data is lower, which has the feasibility of replacing strain gauge. The microscopic morphology analysis shows that the moisture environment affects the epoxy resin bonding fiber, and the matrix swells when it absorbs water. In a thermal environment, the matrix reacts with the outside oxygen. The matrix in the layer shrinks, but it is still bonded to the fibers.

Key words: epoxy resin, carbon fiber composite, wet and hot environments, compressive strength after impact, digital image correlation