Feasibility study on hybrid weld-bonding between dissimilar material for automotive industry

Nowadays, the replacement of steel with lightweight materials such as aluminum causes an increased demand for joining of dissimilar materials in the automotive and aerospace industries. Dissimilar joining of components with Adhesive Bonding (AB) is a widely used method that distributes the load over a greater area than mechanical joints. However, peak stresses at the overlap edges results in premature failure. A solution to alleviate this problem is to implement a hybrid weld-bonded joint to reduce the stress concentration at the edges. In this study, the focus was to manufacture a hybrid weld-bonded joint where Friction-Stir-Spot-Welding (FSSW) was applied at the overlap edges. Tensile shear tests were performed to achieve the fracture load of various joint designs. The fracture surfaces were investigated, and numerical simulation was performed to achieve the fracture load of various joint designs. The fracture surfaces were investigated, and numerical simulation was performed to analyse the fracture mechanism and the interaction between adhesive bond and FSSW. In one of the test series, FSSW was applied in the overlap area near the edges of a similar lap-joint (Al-Al). Here, the adhesive bonding was burnt by the friction of the spinning tool and delaminated. Moreover, the material flow during FSSW was influenced by the presence of the adhesive bonding. To mitigate the interference between AB/FSSW, the spot weld was applied at the overlap edges. The results show that by bringing the FSSW closer to the edge, the bilateral detrimental interaction of AB and FSSW can be significantly reduced. However, the failure load of the hybrid bonded joint was still lower than the adhesive bonded one. Based on the results of the present study, FSSW and AB should be located as far as possible (at least for the selected adhesive) due to their completely different mechanisms of joining. The results can be informative for the development of new hybrid joining configurations with high performance.

Automated summary

Nowadays, the demand for joining dissimilar materials in the automotive and aerospace industries is increasing due to the replacement of steel with lightweight materials like aluminum. Adhesive bonding is a commonly used method for joining components, but it often results in premature failure due to peak stresses at the overlap edges. This study focused on manufacturing a hybrid weld-bonded joint using Friction-Stir-Spot-Welding (FSSW) to reduce stress concentration at the edges. Tensile shear tests and numerical simulation were performed to analyze the fracture load and interaction between adhesive bond and FSSW. The results showed that bringing FSSW closer to the edge can significantly reduce the detrimental interaction between adhesive bond and FSSW, but the failure load of the hybrid bonded joint was still lower than the adhesive bonded one. Based on these findings, the use of FSSW and AB should be located as far as possible to develop new hybrid joining configurations with high performance.