High-performance light steel sandwiches

Important results from the project

To meet the goals regarding reduction of greenhouse gases in road transport new materials are required. In LightFe two steel sandwich concepts, processed by press hardening, with densities 30% lower than density for a solid steel have been developed. The materials meet the high demands on stiffness and good fatigue properties set by the automotive industry. To obtain good crash properties, further development is required. Time efficient FEA to describe the complex core structures has been done. Demonstrators have been manufactured whose performance has been tested and simulated.

Expected long term effects

The sandwich concept (Type I) designed for energy absorption did not show improved crash properties in relation to weight. Hot rolling for joining the perforated core to the outer face sheets gave a too weak bond with delamination as a result. Type II with the ultra-light bicorrugated core showed very good stiffness in relation to weight as well as promising fatigue properties. Computational times using FEA have been reduced by up to 99% through so-called homogenization. Participating companies in LIGHTFe have shown interest in future studied of the latter concept.

Approach and implementation

Two sandwich concepts have been developed where the core has consisted of a perforated sheet and a bicorrugated sheet, respectively. The first concept (Type I) was intended for energy-absorbing components whereas the ultralight bicorrugated core) (Type II) mainly focused on stiffness. Type I was hot-rolled whereas Type II was laser-welded to the thin outer sheets. Time efficient modelling strategies based on homogenization of the cores has been established. To investigate energy absorption, stiffness and fatigue, demonstrators have been manufactured and analyzed with FEA.