On non-linear thermal stresses in an adhesively bonded single lap joint

Since adhesive joints consist of adhesive and adherends with different mechanical and thermal properties, the adhesive and adherends present different stress and strain states under thermal loads due to the thermal–mechanical mismatches. Thermal strains result in serious stresses even though the adhesive joints are not restrained. In this study, the thermal stress analysis of an adhesively bonded single lap joint (SLJ) was carried out considering the large displacement effects. In the thermal analysis, the outer surfaces of the SLJ are assumed to be subjected to air flows with different temperature and velocity. The final temperature distribution in the adhesive joint was used to compute thermal strains. Later, the geometrical non-linear stress analysis of the SLJ was carried out for four adherend edge conditions using the incremental FEM. Thermal strain concentrations were observed inside the adhesive fillets around the free ends of the adhesive layer. The top and bottom surfaces of the adherends also experienced high thermal stresses. The detailed analysis showed that the most critical adhesive regions were the free ends of the adhesive–adherend interfaces. It was observed that thermal loads caused serious stress and strain concentrations in joint members as well as the structural loads (Structural adhesive joints in engineering. London: Elsevier Applied Science; 1984). In order to reduce the peak stresses at the critical adhesive and adherend regions increasing the overlap length was not beneficial for all adherend edge conditions.