Friction Stir Processing of Aluminum for Enhanced Passive Damping: Modeling and Testing of Two Structures

Abstract

Weight is always of high importance in any aerospace application. Increases in performance are necessary while maintaining or reducing weight. Sandwich construction is one way to use light weight materials in aerospace applications. Such structures may be fabricated using friction stir processing (FSP). Friction Stir Processing provides a way to address the issue of increasing the energy absorbing or damping capabilities of a material (damping factor) while maintaining a lightweight structure. The goal of this paper is to investigate analytical and experimental models that would provide insight into the structural dynamics of sandwich plates and other friction stir processed parts. An analytical formulation for treatment of sandwich structure dynamics was investigated in this work. Analytical models were developed for uniaxial bending with cantilever boundary conditions. Free vibrations were considered and validated experimentally. In addition, as part of this project, the impulse response functions of Friction Stir Processed bars were investigated with a view to understanding their damping performance. Results were obtained both from drop testing and flight testing of these bars. Friction Stir Processing proved to be an effective way to passively damp the system. Nomenclature