Experimental studies of subsonic penetration in silica glasses and ceramics

Control and manufacture of light-weight, impact and penetration resistant material systems depend on the response of the component materials to impact loading and on the propagation of stress waves due to different structural configurations. Ceramics are favored as the main component materials in such applications, and thus it is of significance to understand how ceramics resist impact failure and projectile penetration under different conditions of stress wave propagation. In this work, we have undertaken subsonic projectile penetration experimental studies in silica glasses and ceramics to understand how ceramic failure is influenced by reflected tensile and compressive stress waves, pre-shear loading and ceramic target boundaries. A high-pressure gas gun is designed and constructed to launch projectiles up to 1,500 m/s. In borosilicate glasses, experiments show that failure is enhanced by reflected tensile waves, while reflected compressive waves are found to also enhance failure rather than inhibit failure as expected. Experiments in alumina ceramics show that pre-shear loading causes anisotropic failure which induces projectile deflection during penetration. In soda-lime glasses, experiments show that the specific natures of target boundaries control the extent of fragmentation and structural cracking. The behavior of measured quantities are explained with granular flow models of penetration. Granular hydrodynamic models are found to be adequate in explaining fragment ejecta behavior, while the depth of penetration is better explained with granular friction models. Enhancement of failure under dynamic compression in silica glasses is explained with a densification-induced fragmentation model, and this model is found to have potential application on the nature of failure waves in silica glasses.