The effect of hydrothermal ageing on the mechanical behaviour and fatigue response of a hybrid (bolted/bonded) aluminium alloy (AA7075) and glass fibre reinforced epoxy (GRE) hybrid composite single lap joints (SLJs) were carried out in this work. This effect was investigated using hybrid joints as a joint configuration. An adhesive layer of Araldite epoxy and mechanical fasteners of Huck bolt were attached between the adherends as primary and secondary attachments, respectively. Three types of joint were exposed to a humid environment at 50 °C for long-term immersion (20, 40, 60, 80, 100, and 120 days) periods. Composite laminates (i.e. glass fibre epoxy GRE) and metal (i.e. aluminium alloy AA7075) were used as joint adherends. Quasi-static and fatigue tests were carried out to evaluate the evolution of the mechanical performance and the damage mechanisms of hybrid joints during the ageing exposition. The dissimilar-AA7075/GRE hybrid SLJ showed the highest joint strength and the longest failure strain. Moreover, the hybrid joint with dissimilar-AA7075/GRE achieved 83% and 30.2% higher fatigue strength than similar adherends of AA7075 and GRE composites, respectively. As for the damage mechanisms, shear specimens experienced a typical bearing mode.
