Hugoniot states and sound velocities in shock-compressed soda lime glass: Melting and liquid-state response

Commercial silica-rich glasses contain significant fractions of additional oxide cations such as Na and Ca. In particular, soda lime glass (SLG) consists of approximately 71% SiO₂ by weight. To examine the effect of these cations on the shock compression response, plate impact experiments were conducted to determine the high-pressure Hugoniot states and longitudinal sound speeds in shock compressed SLG. The Hugoniot states from 40 – 120 GPa determined from transmitted wave profiles are described very well using a linear U_s-u_p relationship, with no features indicative of a phase transformation. However, the longitudinal sound speeds measured to 90 GPa showed a marked decrease between 52 and 58 GPa, providing experimental evidence for an amorphous solid to liquid transformation. Using the liquid state Hugoniot and sound speeds, the Mie-Grüneisen EOS was determined for liquid SLG. Our results show that the network modifying cations (1) inhibit the crystalline phase transformation observed in shocked fused silica and (2) lower the stress threshold for melting in silica-rich glasses under shock compression. Additionally, sound speed measurements provide a good approach to examine the melting transition in shock compressed amorphous solids, difficult to discern using x-ray diffraction.