Coupled stress-diffusion analysis for durability study in adhesively bonded joints

Coupled stress-diffusion finite element analyses, which are required to study the durability of adhesively bonded joints aged in hot/wet environment, are presented. Two bonded joints have been considered in this study, namely, single lap joint and butt joint. The joints were immersed in water at 60°C for up to 60 weeks. For both joints, transient finite element diffusion analyses have been performed in order to determine the moisture distribution in the adhesive layer at different time intervals. The results of these simulations were coupled to non-linear stress finite element analyses in which the constitutive data of the adhesive was defined as a function of moisture concentration. Four different time intervals have been considered for each joint, namely, 0, 6, 12 weeks and fully saturated condition. The swelling strains have been taken into account in the stress analysis and have been introduced to the adhesive layer according to the moisture distribution at a particular time. These simulations can explain the experimental results of the effect of moisture on joint strength. Further, FE diffusion simulations have been carried out on various configurations of adhesive resin diffusion discs. Together with the experimental mass uptake data these have been used to study the effect of the interface on the moisture sorption.