Distinct wrinkling behavior of metal-polymer-metal sandwich in the forming process: Total sheet wrinkling and surface wrinkling

Abstract

The tunable material properties of metal-polymer-metal (MPM) laminates have garnered significant attention in aeronautical, automotive, and marine industries due to their high specific strength and superior flexural stiffness. Despite these advantages, unavoidable wrinkling during the forming process restricts their broader application in industrial manufacturing. In this study, the wrinkling behavior of MPM laminates in the deep drawing process was investigated through theoretical analysis, experimental observation, and finite element analysis (FEA). Two distinct wrinkling behaviors were identified along the predicted wrinkling line based on the energy method. Beyond the wrinkling line, surface wrinkling occurred even under a high blank holding force (BHF), indicating the susceptibility of MPM laminates to wrinkling. In the case of surface wrinkling, the strain energy decreased due to the shifting of the neutral axis and the potential energy of BHF significantly decreased with deformed thickness. This phenomenon was attributed to the lower elastic modulus of the soft core and buckling-induced delamination, leading to a reduction in the energy required for wrinkling. The effect of soft-core elastic modulus was further evaluated through post-buckling analysis, including modal analysis via FEA. A stiffer core was expected to stabilize the mode shape of the sheet and prevent wrinkling without altering the overall properties of the laminate. This study highlights surface wrinkling as a critical deformation mode in layered systems and proposes material design strategies to enhance the formability of MPM laminates.