Experimental determination of Grunieisen gamma for two dissimilar materials (PEEK and Al 5083) via the shock-reverberation technique

Following multiple loading events the resultant shock state of a material will lie away from the principle Hugoniot. Prediction of such states requires knowledge of a materials equation-of-state. The material-specific variable Grunieisen gamma ($\Gamma )$ defines the shape of ``off-Hugoniot'' points in energy-volume-pressure space. Experimentally the shock-reverberation technique (based on the principle of impedance-matching) has previously allowed estimation of the first-order Grunieisen gamma term ($\Gamma _{1})$ for a silicone elastomer. Here, this approach was employed to calculate $\Gamma _{1}$ for two dissimilar materials, Polyether ether ketone (PEEK) and the armour-grade aluminium alloy 5083 (H32); thereby allowing discussion of limitations of this technique in the context of plate-impact experiments employing Manganin stress gauges. Finally, the experimentally determined values for $\Gamma _{1}$ were further refined by comparison between experimental records and numerical simulations carried out using the commercial code ANYSYS Autodyn{\textregistered}.