Flexural fatigue behaviour and damage mechanism of polystyrene bead foams—Influence of the foam density

Abstract

Polystyrene-based bead foams are used in various applications under non-steady loading conditions, ranging from sports protectors to automobiles. However, the cyclic dynamic behaviour of bead foams and the influence of density on flexural fatigue behaviour have not yet been investigated. In this context, an analysis is conducted on both the morphology of the foam beads and the resulting morphology of the moulded parts produced from these beads. Furthermore, the influence of density on the quasi-static compressive and flexural properties was investigated. These results serve as a basis for conducting load-controlled flexural fatigue tests on various dense bead foams.It was found that the density dependence of the mechanical properties in the quasi-static tests follows the power law. In the flexural tests, the predominant damage mechanism is mainly influenced by the foam density but also by the processing.Surprisingly, the specific dissipated energy and stiffness remain constant for different densities until fast progressing failure occurs. Design criteria can be derived from the fatigue results. Under fatigue load, the stress should not exceed 40% of the quasi-static flexural strength, regardless of density.