Experimental study of shock wave structure in syntactic foams under high-velocity impact

Behavior of spacecraft structural materials under the high-velocity impact should be thoroughly investigated due to the constant threat of collision with space debris and meteoroids. Syntactic foams are perspective lightweight composite materials for spacecraft protection capable to attenuate shock waves. The shock response of highly filled syntactic foam to uniaxial planar impact loading was investigated using a powder gun facility and a laser velocimeter technique. The studied 0.64 g/cm(3) foam consisted of an epoxy matrix filled with 55% volume fraction of glass microspheres. Measured wave profiles demonstrate the complex two-wave configuration associated with formation of precursor and compaction waves. Hugoniot and strain-rate data for the syntactic foam are presented in the stress range of 0.28-0.7 GPa. The Hugoniot elastic limit are determined to be 0.12 GPa, which implies that a precursor cannot be neglected in shocked state calculations in the studied loading regime. The density of the foam decreases with increasing loading stress due to thermal effects. The effect of sample thickness on wave fronts, wave velocities and precursor amplitudes is described. Precursor waves did not reach stable states in the experiments.