Impact behaviour of 3-layered metal-polymer-metal sandwich panels

Ductile 3-layered sandwich panels made of metal cover sheets and a polyolefin core were produced with different layer thicknesses of core and cover sheets in laboratory scale. Because of their lightweight potential, they are interesting for the use in automotive, nautical and even aviation applications. Their impact behaviour is changing, depending on their material and geometrical conditions (quality of the metal and polymer, thickness of the different layers). Therefore, impact tests were performed to investigate this effect, using a steel-polyolefin combination with varying thicknesses of the layers and measuring the post-impact deflections. The results show that all the considered factors influence the panels’ crashworthiness. With the aim of studying the mechanical behaviour of damaged specimens, post-impact tensile tests were performed. Tests were monitored by thermography, a valid technique able to identify the presence of a damaged region in the panels before reaching the yielding stress. A discussion on the obtained experimental results proposes some parameters to identify and quantify the impact damage: the specific deflection and related area, the strain to failure and the damage stress from thermography.