Water ageing effect on the strength of adhesively bonded joints

Moisture absorption and behaviour in water environment are major concerns for materials as reinforcement in composites. This paper presents a study on the influence of water ageing on mechanical properties and damage locations of the adhesively bonded joint. To this goal, three combinations of adherends were investigated: similar aluminium/aluminium, similar composite/composite and dissimilar aluminium/composite. All joints were bonded using two parts paste of Araldite epoxy adhesive. The vacuum bagging was used to produce composite adherends. The joints were aged in tap water at a temperature of 50 °C for several days of exposure (20, 40, 60 and 80 days). The effect of the immersion treatment on the tensile properties and water absorption were investigated through experiment. Overall, three replicates of joints were characterized by performing single lap joint (SLJs) tests. The moisture absorption results showed that percentage of water absorption increases with increasing of immersion exposure for each materials combination with unsaturation. The reduction of joint tensile strength was observed for each joint materials with the increasing of immersion periods. The huge reduction gap or percentage of dry and wet specimens were detected on similar composite/composite with nearly 50% at the first 20 days of immersion. The damage location and failure of the joint have been observed with cohesive and adhesive failure.