Sound velocities in shock-compressed soda lime glass: Melting and liquid-state response

Abstract

Longitudinal sound velocities (and elastic moduli) were determined in soda lime glass (SLG) at peak shock stresses ranging between 40 and 90 GPa. Laser interferometry was used to obtain particle velocity histories and sound velocities by impacting SLG samples on lithium fluoride (LiF) optical windows. In all experiments, the SLG response consists of a sharp jump to a constant state followed by a release wave. The measured longitudinal sound velocities and moduli showed a marked decrease between 52 and 58 GPa, providing experimental evidence for the transformation from an amorphous solid to a liquid in shock-compressed SLG. The stress threshold (\ensuremath{\sim}55 GPa) for melting in SLG is considerably lower than the threshold reported in shock-compressed fused silica (\ensuremath{\sim}72 GPa), showing the effect of network-modifying cations on the onset of melting. The relative values of sound velocities, shock velocities, and the Hugoniot slopes---between 58 and 90 GPa---are fully consistent with the thermodynamic response of a shock-compressed liquid. Using the experimental results, the Gr\"uneisen parameter (\ensuremath{\Gamma}) values were determined for liquid SLG to 90 GPa and then used to provide the Mie-Gr\"uneisen equation of state for liquid SLG.