Effect of hygrothermal-mechanical exposure on the residual strength of adhesively bonded joints

The strength durability of adhesively bonded joints under combined mechanical and hygrothermal environments is crucial for their industrial application. In this study, the strength durability of adhesively bonded aluminium-lithium alloy joints under combined hygrothermal-mechanical conditions was investigated, three loading regimes were applied to the joints and four different hygmthermal conditions were selected. The strength degradation, failure modes, fracture morphology, and adhesive characteristics after exposure were analyzed. The results indicated that hot-humid conditions are the main causes of strength degradation compared to applied loading, however, sustained loading accelerates the rate of degradation, which is more pronounced as the temperature, humidity, loading levels, and exposure cycles increase, especially for the joints to which combined loading is applied. The joint strength degraded by 15.9% without loading application, while it reduced by 19.7%, 19.0%, and 21.8%, respectively, for tensile, bending, and combined sustained loading under temperature cycling from -40 degrees C to 80 degrees C and humidity cycling from 30% to 95%.