Polymer foam crash components subjected to low velocity impact

Abstract

The automotive industry has increased its use of energy absorbing systems in recent years. These components can involve sandwich structures consisting of two skins with a core material between them. The core is often a light and soft cellular material such as a foam. The sandwich structure is traditionally used as a structural element with high specific bending stiffness and strength [1], but today car manufacturers also use foams inside other structural elements for passive safety in a crash situation [2]. This paper is part of a larger ongoing experimental investigation [3], where we have examined the behavior of two types of polymeric foams as core material in a sandwich component. These are extruded polystyrene XPS-700 and expanded polypropylene EPP-5130, both with a density of 50 kg/mm3 . First, we carried out material tests to reveal the mechanical properties of the polymeric foams. Then, we conducted low-velocity impact tests on sandwich targets consisting of skins of Docol 600DL steel and the two different foam materials as core. The impact tests were performed in a drop tower, where the mass was kept constant at 15 kg, while the impact velocity varied between 5 and 10 m/s. High-speed cameras and 3D-DIC were used to measure the out-of-plane deflection of the structures. Even though the mechanical behavior of the two foams was found to differ quite significantly, the energy absorption of the crash components during impact was found to be similar, especially at low velocity impacts.