The Equation of State of Silica, Polystyrene, and Periclase from Strong Shock Compression

Chad August McCoy, Ph.D. Defense

Hopeman 224

Knowledge of the equation of state is essential for understanding and predicting the behavior of a material at high-energy-density conditions (100 GJ/m³).  Shock-wave experiments have been used to produce these conditions but the resulting end states are confined to the Hugoniot.  One method to study a broader region of the thermodynamic plane is to acquire measurements of differential quantities (e.g. sound speed and Grüneisen parameter) in the shocked material.  Knowledge of these quantities allows one to model the material behavior as it moves away from the Hugoniot.  We present measurements of the principal Hugoniot, sound velocity, and Grüneisen parameter of fused silica, polystyrene, and periclase in the high-pressure regime.  These used a novel technique relating the propagation of acoustic perturbations in a sample to those in a standard with known sound velocity and Grüneisen parameter.  The arrival of correlated perturbations at the shock front in each material provides information on the relative sound velocities in those shocked materials.  Updated shock velocity-particle velocity Hugoniot relationships were developed and sound velocity and Grüneisen parameter measurements were compared to existing EOS tables.