DYNAMIC COMPRESSION CHARACTERISTICS OF FLEXIBLE FOAMS .1. SIMILARITY MODEL, ANALYSIS, AND EXPERIMENTS

A simple mathematical model is proposed, based on dimensional similarity parameters, to describe the characteristics of flexible plastic foams under impact conditions. The model assumes that the foam is rate-dependent material, when the dynamic stress is a function of the strain and the strain rate. The similarity parameters include the geometric dimension of the foam, the mass of the absorbing body, and the drop height. By using this model, one can predict the maximum deformation, the maximum decelerations, and the time-pulse period for a wide range of drop heights and masses, by conducting several drop tests. We verified the efficacy of this model by performing free-fall drop tests with flexible polyurethane foam having a uniform density of 240 kg/m**3.