Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al-Mg-Cu alloy

The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid-state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024-T3 Al-Mg-Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints.