On the response of ballistic soap to one-dimensional shock loading

The effects of projectile penetration into soft tissue are often studied using the tissue simulant ballistic soap. Consequently, a full understanding of the high strain-rate response of ballistic soap is desirable. Using the plate-impact technique, key shock parameters have been measured for impacts in the range 81–968 m/s, allowing derivation of the Hugoniot equation-of-state for soap in the US–uP and σX–uP planes. A polynomial Hugoniot relationship was found in the US–uP plane, with the general form US = 1.96 + 2.41uP − 0.72uP2 (ρ0 = 1.107 g/cc). Further, embedded lateral manganin stress gauges were employed to interrogate the evolution of lateral stress within the soap. A gradient in lateral stress, whose magnitude increased incrementally with impact stress, was apparent behind the shock for σX >1 GPa. It is proposed that at higher values of σX, increased compression of hydrocarbon chains acts to increase the materials resistance to shear, a phenomenon consistent with steric hindrance.