The formability of aluminum foam sandwich panels

Abstract

The present paper aims to study the formability of Aluminum Foam Sandwich (AFS) panels. At now, the final shape of foamed devices is directly obtained through the foaming process itself and no further shaping steps are expected. In any case, further manufacturing processes may be exploited to produce more complex parts. Among forming operations, bending can be regarded as one of the simplest processes for both study and application. Besides, bending tests may yield interesting information about material properties. With regard to the metal foams characterization, several bending tests on AFS panels fabricated by Alulight® were carried out by varying the process conditions. A universal testing machine was employed for this purpose, collecting data about the deformed geometry and about load vs. displacement. Even though the samples deformation was related to the occurrence of foam cells failure or collapse, once the process was terminated, they still retained a significant bending strength. The metal foams properties were also investigated using both non-destructive and mechanical tests. In particular, thickness measurements (using an ultrasonic feeler), X-ray analysis and foam density measurements were carried out on AFS specimens before the execution of both upsetting and bending tests. Finite Element simulations of the foam bending process were performed to investigate stress and strain distributions on the specimens. In particular, an isothermal plane strain model of the bending process was setup using the FEM commercial code Deform 2D. The results of this study were used to produce closed structure components (square shapes) by combining three 90° bends. A further improvement consisted in joining the open ends, to enhance shear and torsion resistance. Among joining techniques conventional welding processes (Tungsten Inert Gas—TIG and laser) and a non-conventional method (Friction Stir Welding—FSW) were investigated. Finally, the mechanical properties of the joints were characterized using both three and four point bending tests.