Effect of hygrothermal ageing on the mechanical performance of CFRP/AL single-lap joints

Bonding technology presents several advantages over traditional mechanical connecting methods and, thus, has been widely used in the automotive industry. However, hygrothermal ageing environments may exert a significant degradation effect on the bonding structure during the service of the automobile. This study mainly investigated the effect of hygrothermal ageing on the quasi-static tensile strength of the adhesive layer of carbon fiber reinforced plastic (CFRP)-aluminium alloy (AL) single-lap joints (SLJs). A simple method, based on the finite element (FE) model, was used to determine moisture-dependent CZ properties. Numerical simulations of the quasi-static tensile properties of the CFRP/AL SLJs were also conducted, and the simulation results were consistent with the experimental findings. Results indicated that the failure strength of the adhesive and adhesively bonded CFRP/AL SLJs subjected to hygrothermal ageing declines with increasing ageing duration. Moreover, the degradation rate in the initial stages of ageing is significantly higher than that in later stages. Failure of the adhesively bonded CFRP/AL SLJs was characterised by cohesive failure and mixed failure. No carbon fiber delamination was observed in CFRP/AL SLJs following hygrothermal ageing.