Deformation response of EPS foam under combined compression-shear loading. Part I: Experimental design and quasi-static tests

Expanded Polystyrene (EPS) foam material is widely used as an energy absorption engineering material. Its compression behaviour, both quasi-statically and dynamically, has been studied widely. However, its mechanical behaviour under combined compression-shear loading is poorly understood due to the difficulty of performing such tests. A novel test rig is presented to perform combined compression-shear loading tests in quasi-static and high strain rate dynamic conditions. Different densities of EPS foam were tested with this apparatus using a universal testing machine and a drop tower. The compressive and shear stress and strain curves were obtained and compared with the mechanical behaviour of EPS foam under pure compression. This showed that the shear deformation of EPS foam under combined compression-shear loading tends to lower the compressive stress at yield of the foam up to 40% compared with pure compression, depending on the density of the foam. A companion Part II paper will separately present and discuss the experimental results of the high strain rate dynamic tests of EPS foam under combined compression-shear loading.