Structural and impact behaviour of an innovative low-cost sandwich panel

The classic sandwich structure consists of two thin and stiff face sheets and a thick, lightweight and stiff enough material in between. Although this structure seems optimal, in practice the large differences between the structural properties of the materials in contact create many problems. Moreover, the cost of the existing core materials is very high, pushing towards the selection of the cheap cores. Of course, the final selection of the core material is a compromise between the cost, the weight and also other characteristics of the core such as the impact resistance, fatigue, moisture, etc. To improve the efficiency of the sandwich structures, two innovations are proposed: firstly to use metal skins instead of composite ones and to introduce an intermediate layer between the outer skins and the foam core. This layer should be much stiffer than the core material, lightweight enough and preferably thicker than the face sheet. This intermediate layer allows for the use of very thin face sheets, e.g. metals, and very cheap cores, e.g. polystyrene or polyurethane foams. Furthermore, if a common material is used for the intermediate layer, e.g. wood, the cost will also decrease considerably. In this paper the structural behaviour of this new sandwich concept, together with its impact behaviour, has been studied on the basis of tests performed with impactors dropped from 3.6 m producing impact energy up to 36 J.