Experimental study on hygroscopic absorption and low-velocity impact of CFRP treated in damp and hot environment

Pure resin and modified Carbon Fiber Reinforced Polymer (CFRP) laminates at 45/0/−45/90_2S lay-up angle were prepared using modified carbon nanotubes and modified nano-SiO₂ for the epoxy resin modification treatment, followed by vacuum-assisted resin transfer molding (VARTM) molding process. Two different conditions of hygrothermal aging treatments were carried out respectively, after which the hygrothermal samples were subjected to drop-hammer impact experiments and internal damages were characterized by ultrasonic C and scanning electron microscopy. The results show that the high temperature has the greatest effect on the equilibrium moisture absorption and water diffusivity of CFRP samples, with carboxylated multi-walled carbon nanotubes(Hydroxylated MWCNTs) being more effective than nano-SiO₂. The equilibrium moisture absorption rates of the three samples were 0.647%, 0.605%, and 0.583% at 70°C 85% RH, and 0.264%, 0.233%, and 0.223% at 30°C 85% RH, in that order; there are multiple mechanisms of nanoparticles interacting with the internal loss during the moisture absorption process, which has an inhibitory effect on the absorption of water; the hygrothermal aging will have an effect on the laminate mechanical properties, and the high temperature and high humidity environment has a greater effect than normal temperature and high humidity.The addition of nanoparticles improved the impact resistance of CFRP materials, and the impact resistance of CFRP with carbon nanotubes was higher than that of nano-SiO₂, but the impact resistance of damp heat aging, the CFRP with carbon nanotubes was the worst, followed by nano-SiO₂, and the best without particles.