Advances in Refill Friction Stir Spot Welding

While rivets are the prominent choice for joining skin-stiffened aluminum structures, the current study focuses on the use of refill friction stir spot welding for assembly of skins and skin-stiffened structures. Aluminum lithium skins were produced with and without sealant to evaluate production quality, distortion, and other key measures of quality for overlapping skin assemblies. Refill friction stir welding was also applied to joining high strength aluminum extrusions to fuselage skins to produce skin-stiffened structures, with a focus on weld development for near edge joining at low-cycle times. Evaluation of weld properties including quasi-static lap-shear, fatigue are presented in comparison with traditional riveted joints, as a means of comparison. An analysis of manufacturability of skin-stiffened structures produced via refill friction stir spot welding is presented, to provide detailed analysis related to process performance, machine dynamics, tool life and overall material properties.