On the influence of fsw in the elastoplastic buckling load-carrying capacity of extruded integrally stiffened panels for aeronautic applications

Abstract

Reinforced structures for aircraft fuselages are conventionally composed by base (skin) aluminium plates and reinforcement elements (stringers), joined by riveting operations. During the last decade more effective approaches for reinforced fuselage and wings, such as the Integrally Stiffened Panels (ISP), have appeared. These homogeneous reinforced structures are obtained in an integral form by extrusion, allowing for lower manufacturing costs. During service conditions, these structures can be subjected to extreme compressive loading conditions and, due to their slenderness and low weight, ISP design must account for a reliable determination of buckling loads. However, complexities of the cross-sectional geometrical shapes, together with the occurrence of elastoplastic non-linear effects prior or after buckling, completely impair the use of analytical tools, being the analysis by the Finite Element Method (FEM) imperative in a reliable design process. In the present work, the structural performance of ISP structures is assessed, accounting for buckling in the elastoplastic range, by means of numerical simulation with the Finite Element Method. Also, the buckling load-carrying capacity of multiple sets of reinforced structures, composed by a finite number of ISP and joined by friction stir welding (FSW) operations, is also studied. In doing so, it is possible to numerically infer about the influence of the presence of FSW zones in the overall stiffness and mechanical behaviour of ISP structures with complex cross-section geometries.