Influence of mid-stress on the dynamic fatigue of a light weight EPS bead foam

Abstract

Expandable Polystyrene (EPS) is one of the most commonly used material, when it comes to protect thermal sensitive goods, since the thermal conductivity of EPS is very low. The mechanical properties in terms of long-term compression or quasi-static compression are also quite well known. But when the material is loaded with higher amplitudes over a long period of time, not much is known yet about long-term mechanical behavior. For example, as a packaging material, EPS exhibits complex loading situation ranging from small to high amplitudes over a long period of time, when e.g. it is transported in a truck, a ship or in a car. In order to characterize the mechanical behavior under such large amplitude loading, the dynamic fatigue needs to be recorded and evaluated. In this paper, the principles of the hysteresis measurements evaluation are applied on EPS for the first time to unveil long-term mechanical properties in compression. Results show, that after increasing the dynamic load level to a critical level of over 100 kPa, the mechanical behavior, in terms of compression rate, of EPS changes from a linear to a kind of exponential mode.