Collapse behaviour of foam shock pads

The onset and end of the collapse phase (stress and strain) were determined in three closed cell PE and one open cell PU foams. In general, foams with higher densities collapse at smaller strains and show smaller collapse rates. The higher the density of the PE foam is, the higher is the percentage of buckled elements at the elastic collapse strain. The elastic collapse stress thus represents the end of the collapse phase rather than its onset. The PU foam (relative density 0.27) showed an elongated collapse plateau and a small collapse ratio.