1994 Volume 37 Issue 2 Pages 268-274
Shock wave propagation in polyurethane (PU(R)) foam was experimentally studied. The experiment was conducted in a shock tube by measuring pressure along the PU(R) foam in a shock tube, by means of holographic interferometry and streak camera recording. It was found that the stress-strain curve of PU(R) has an inflection point. When the pressure behind the incident shock wave was below the inflection-point pressure Pc, the wave impedance ratio of the incident shock wave and transmitted pressure wave Zi/Zt increased sharply. This indicates that only a small amount of energy is transmitted into the foam if the pressure is below Pc. For pressures larger than Pc, Zi/Zt decreases asymptotically to a small finite value.