On impact upon brittle solids

The response of brittle materials to uniaxial compressive shock-loading has been the subject of much recent discussion. The physical interpretation of the yield point of brittle materials, the Hugoniot elastic limit (HEL), th e rate-dependence of this threshold, and the effect of polycrystalline micr ostructure still remain to be comprehensively explained. Evidence of failur e occurring in glasses behind a travelling boundary that follows a shock fr ont has been accumulated and verified in several laboratories. Such a bound ary has been called a failure wave. The variations in properties across thi s front include complete loss of tensile strength, partial loss of shear st rength, reduction in acoustic impedance, lowered sound speed and opacity to light. Recently we have reported a similar behaviour in gabbro and the pol ycrystalline ceramics SiC, alumina and titanium diboride. It is the object of this work to present further observations of these phenomena and their r elation to ballistic performance.