ONE-DIMENSIONAL SHOCK-WAVE INTERACTION WITH RUBBER AND LOW-POROSITY FOAM

One-dimensional interaction between a planar shock wave and a rubber o r low-porosity foam is investigated experimentally and numerically. Th e considered polyurethane foam is of high density (rho(c) = 290 kg/m(3 )) and low-porosity (phi = 0.76), and this corresponds to an intermedi ate condition between rubber and high-porosity foam. Stress-strain rel ations for the low-porosity foam are investigated by machine tests, wh ich show larger deformation against compressive force and higher non-l inearity in stress-strain curve as compared with rubber. Also the low- porosity foam shows a hysteresis cycle. Experiments on shock wave-foam interactions are conducted by using a shock tube. Experimental time h istory of the surface stress of the foam at the end of the shock tube does not show shock type stress increase, but continuous excessive str ess rise can be seen, and then dumping vibration approaching to gas dy namic pressure of the reflected shock wave is followed, and the highes t stress amounts about 3 similar to 4 times of the pressure after the reflected gas dynamic shock wave. Interactive motions of gas and the l ow-porosity foam are analyzed using the Lagrangean coordinates system. An elastic model for a low-porosity foam is assumed to be a single el astic material with the measured stress-strain relation. Results of nu merical simulations are compared with the shock tube experiments, whic h show essentially same stress variations with experimental results.