Crashworthiness of Thin Ultra-light Stainless Steel Sandwich Sheets: From the Design of Core Materials to Structural Applications

Thin sandwich sheets hold a promise for widespread use in automotive industry due to their good crash and formability properties. In this paper, thin stainless steel sandwich sheets with low-density core materials are investigated with regard to their performance in crashworthiness applications. The total thickness of the sandwich materials is about 1.2mm: 0.2mm thick facings and a 0.8mm thick sandwich core. Throughout the crushing of prismatic sandwich profiles, the sandwich facings are bent and stretched while the sandwich core is crushed under shear loading. Thus, a high shear crushing strength of the sandwich core material is beneficial for the overall energy absorption of the sandwich profile. It is shown theoretically that the weight specific shear crushing strength of hexagonal metallic honeycombs is higher than the one of fiber cores - irrespective of their relative density or microstructural geometry. On the structural level, we compare the crushing response of prismatic structures made of thin sandwich sheets with (i) a fiber core made of 25μm thick stainless steel fibers that are bonded perpendicularly to the sandwich facings, and (ii) a micro-cell honeycomb that is made of 40μm thick stainless steel foil. The results demonstrate that that the use of the micro-cell honeycomb doubles the specific energy absorption.