Numerical simulation and failure experiment of hygrothermal aged CFRP single and double lap joints

In this paper, we compare the failure behaviors of CFRP single and double (S–D) lap joints and analyze the effects of hygrothermal aging on these joints through a comprehensive experiment and simulation. Firstly, we analyze and compare the degradation pattern of the residual strength of S–D​ lap joints under three hygrothermal environments, and reveal the aging mechanism in conjunction with the macro/fine-view failure surfaces of the joints. Secondly, we elucidate the probability distribution of joint aging failure using the two-parameter Weibull distribution. Finally, we develop a finite element model to simulate the failure process of the cohesive behavior, and compare not only the bending moment and contact stress distribution of the two joints, but also analyze the damage condition of the CFRP matrix/fiber. We define environmental degradation factors to express the failure behavior of lap joints after aging. Through the above analysis methods, we find that hygrothermal aging can seriously damage the CFRP and adhesive properties. The mechanical performance of DLJs is significantly superior to that of SLJs, and they also exhibit better reliability. Therefore, DLJs can be substituted for SLJs in some application scenarios. Additionally, our paper provides new insights into the selection of an appropriate lap bonding method.