Influence of high temperature exposure on the mechanical performance of double-lap adhesive joints between glass and aluminium adherends

The present paper illustrates an experimental investigation on double-lap adhesive joints between glass and aluminium adherends. Four different commercial structural adhesives (three epoxies and one urethane) are selected for tensile tests on adhesive joints subjected to different loading conditions (i.e. quasi-static and cyclic) and high temperature exposures (85 degrees C). The main objective is to verify the mechanical performance and the applicability of the joint in the field of civil engineering. The results show - after curing under laboratory conditions (20 +/- 1 degrees C/50 +/- 5% RH) - a good adhesion between the tested materials. A suitable mechanical behaviour for the assembly of building components with adhesive technology is observed. The first epoxy adhesive shows the best performance both in terms of stiffness and ultimate load, which is due to a better and complete catalysis of the two components of the epoxy adhesive. Exposure to a heating (85 degrees C) and cooling (20 degrees C) cycle shows a positive effect on the mechanical performance of the joints. An increase in stiffness and ultimate loads is observed for the first and second epoxy and urethane adhesives. Cyclic loading/unloading tests performed after each heating (85 degrees C) and cooling (20 degrees C) process - up to ten repetitions - show a nonlinear trend of displacements and stiffnesses. However, at the end of each loading/ unloading cycle, an increase in the ductility of the joint is observed. Moreover, a short exposure of the joints to high temperatures (85 degrees C) leads to an improvement in the failure modes: mixed failure modes are observed, with CF and GF failure rates coexisting with adhesive failures. Prolonged exposure to high temperatures has a negative effect on the failure modes of the joints and leads to an increase in the percentage of adhesive failures.