Experimental and numerical evaluation of formability in three-layer metallic sheets with various layer arrangements

Abstract Multi-layer metallic sheets are composed of two or more metallic layers connected to each other to achieve desirable features based on the various properties of the constituent layers. This study attempted to predict the forming limits and deformation behavior of three-layer metallic sheets. Additionally, the effects of the layer arrangement on the forming limit diagram (FLD), stress triaxiality, and limiting dome height (LDH) were investigated using a finite element numerical approach. To this end, three-layer metallic sheets made of aluminum (AA3004), stainless steel (SUS304), and copper (Cu1011) bonded by polyurethane as the bonding layer were employed. The numerical results were validated using the experimental results of Nakajima stretch-forming tests. The numerical results were in good agreement with the experimental data. The results indicate that the formability of the three-layer sheet increased by placing the AA3105 layer as the inner layer in contact with the punch, the Cu1011 layer in the middle, and the SUS304 layer as the outer layer. Therefore, the formability of the Al-Cu-SUS sheet was higher than that of the other layer arrangements. Moreover, the results show that the material properties, particularly the tensile strength, play a key role in controlling the FLD of the three-layer sheets.