Experimental and numerical analysis of springback and bending behavior of a composite sandwich metal-polymer material

Abstract

Lightweight design, lower fuel consumption and easier recyclability are the current concerns of the automotive industry as a response to the increasing demand for energy saving and better environmental impact of the transportation section. This framework was the opportunity to develop multi-layer materials, as an alternative to the high-density homogeneous metal sheets, maintaining the structural properties of the component. The multi-layer materials, known as composite sandwich or hybrid materials, are composed of outer metal sheets with reduced thickness and a polymeric matrix core (low density), in which high specific strengths are achieved. However, the lack of studies and information about the behavior of these non-homogeneous materials posed new challenges, either with regard to their use in the sheet metal forming processes, but also when performing material mechanical characterization. This paper presents the problems faced with bending test and springback analysis of a sandwich metal polymer sheet, compared with a high strength low alloy steel (HSLA420). Experimental tests and corresponding numerical simulations were performed using the press brake air bending process and a Numisheet benchmark test, unconstrained bending test, at room temperature, using the same experimental conditions for both materials. The numerical simulations were performed using finite element modeling. The results show that the sandwich material have problems on the structural integrity for a lower punch radius, on the outer surface (tension side). Additionally, the comparison of springback behavior showed that there is no significant difference between the materials in the study, although the non-homogeneous sandwich material presented a lower springback.