Study of shear and compression waves in shocked calcium carbonate

In-material transverse and longitudinal particle velocity histories were measured in Carrara marble (polycrystalline calcium carbonate) under combined compression-shear, plate impact loading to peak levels between 0.5 GPa and 5 GPa (0.8% to 11% density compression). To accurately time-correlate the shear and compression waves, a method was implemented to simultaneously measure individual particle velocity components in a single experiment.;The shear waves were dispersive. They had significant amplitudes over the entire range investigated, suggesting the marble retains strength up to 5 GPa. The longitudinal waves had an unsteady and complex structure, including a rarefaction shock, suggesting the occurrence of phase transformations and yielding.;Shear, compression, and longitudinal release wave speeds were determined from the measured histories. Longitudinal stress and density were calculated from the measured histories using a surface fitting method to analyze non-self-similar waves. The shear and bulk moduli in the shocked marble were determined from the measured wave speeds and calculated peak densities.;The locus of peak longitudinal stress-density states is offset substantially above the hydrostat for single crystal calcite except at the highest peak stress, suggesting shock and hydrostatic loading might produce the same phases above 4.5 GPa.;The shear wave speeds in the shocked marble exhibit a decrease associated with the calcite-CaCO;The bulk modulus values agree reasonably well with hydrostatic data up to 9% compression. At 11% compression, the shock datum falls substantially below the hydrostatic data. This result demonstrates that it is inappropriate to infer production of CaCO;Because the measured wave speeds provide frozen phase-composition bulk modulus values, the peak mean stress is not obtained from the integral of the experimentally-determined bulk modulus values.;A process of transformation-enhanced plasticity, observed under hydrostatic loading, is suggested to contribute to the features in the compression waves.