Effect of hollow adherends on stress peak reduction in single-lap adhesive joints: FE and analytical analysis

The study of the stress distribution in the adhesive layer is fundamental for the prediction of the mechanical behaviour and of the strength of the joint. The joint failure is determined by the stress distribution and by the presence of stress peaks. This paper analyses the stress distribution in a single-lap joints and proposes a method to reduce stress peaks using hollow adherends in the bonding region. A single-lap joint between GFRP adherends and two different structural adhesives (epoxy and urethane) is numerically analysed, considering different geometric configurations (i.e., hollow cross-section with different geometric properties). The asymmetric use of the hollow cross-section causes an increase in the stress peaks in the bonded region. This is due to the increase of the bending moment, determined by the geometry of the joint. Moreover, the distribution of the hollow sections over both adherends showed positive effects on the reduction of the stress peaks in the adhesive layer. The largest reduction of the stress peaks is observed for the section with the highest slot on both adherends. The FE results showed the possibility to significantly reduce the stress peaks, and at the same time reduce the weight of the adhesive joint.