Static Strength Comparison of Riveted versus Friction Stir Welded Stiffened Panels

Abstract

Friction stir welding (FSW) is a rapidly emerging joining technology that is finding greater use in aerospace applications due to significant advancements in tooling and process development. However, basic performance and design parameters for aerospace structures incorporating FSW joints have typically been developed on a case by case basis and are not yet available for general applications. Performance and properties data are needed to advance FSW from coupon level research to direct application. Therefore, the National Institute for Aviation Research (NIAR) initiated an investigation to compare the integrity of typical airframe structure joined using FSW with that of riveted structure. Ultimately, the aim of this investigation is to aid in the development of performance specification data. The structures selected for this research were subscale flat stiffened panels that were based on previously developed designs from generic fuselage applications. The initial stiffened aluminum panels were fabricated with two hat-section stiffeners. Representative of a transport fuselage design, the skin panels were 0.040-in 2024-T3, and the stiffeners were 7075-T6 spaced on 8.0 inch centers. The 2-ft x 2-ft stiffened panels were tested statically in tension, compression, and shear. Finite element models were developed to evaluate the ability of modeling to predict the load carrying capability of FSW structures. In the presentation, test results from riveted panels with identical geometry will be compared with results from both the models and the FSW panels. To date the panels fabricated using FSW have shown an increase in overall performance including an increase in panel strength and axial displacement. The FSW shear panels failed less abruptly and with much less destruction than did the riveted panels, indicating an increase in the ability of the FSW panels to sustain damage.