Stiffness of Expanded Polystyrene Foam for Different Stress States

This paper examined the stiffness of expanded polystyrene foam (EPS) with monotonic and cyclic loading under different stress states. The test program was performed for monotonic loading and cyclic loading. The stiffness of geofoam subjected to monotonic loading increased with increasing density. The solid skeleton empirical equation was proposed to predict the geofoam modulus with different densities. The distortional ratio of the EPS decreased with reduced density and increased stress ratio and substantially decreased when the stress was above the elastic limit. The dynamic modulus was higher than the initial modulus with a low stress ratio and began lower than the initial modulus when the stress ratio was over 0.9. The dynamic modulus of the geofoam substantially increased with increasing density and slightly decreased with increasing stress ratio and decreasing load frequency. The proposed empirical equation can reasonably predict the dynamic EPS stiffness with varying densities, stress ratios and loading frequencies.