Corner Stationary Shoulder FSW for Aerostructures
By Jeroen De Backer (TWI Ltd.), Anthony Mc Andrew (TWI Ltd.), Jorgen Sall (ESAB AB), Mattias Jonsson (SAAB AB)

The replacement of riveted by welded aerostructures offers the potential to reduce manufacturing time and cost. By introducing the corner stationary shoulder friction stir welding process (CSS-FSW), the overlapping flanges in a stiffener-skin applications can be eliminated entirely and there is no need for sealant or rivets, allowing significant weight reductions. This paper describes the objectives and results from an ongoing Horizon 2020 Clean Sky collaborative research project. The development of CSS-FSW weld procedures for T-joints of AA2024-T3 to AA7050 will be described along with microstructural analysis of the joint and mechanical properties. The benefits and limitations of the process and the introduction of a machined 'elephant foot' on the stiffener will be discussed. Finally, a cost and weight saving projection is made for replacement of rivets by CSS-FSW on representative aerostructures.