Propagation of fracture and damage phenomena in glasses at high dynamic loadings

Four different types of glasses (float glass, optical glasses K5, F6, SF6) were impacted by pointed and blunt projectiles of different diameters within a velocity range from 10 m/s up to 1600 m/s. The propagation of fractures was observed by means of a 24-spark high-speed camera in a shadow-optical arrangement. In addition to the fractures generated at the impacted edge of the glass slabs, crack nuclei were activated by the longitudinal shock wave if the transferred energy was sufficiently high. All types of cracks observed propagated with terminal crack velocity. In order to describe the damage of the targets by the different phenomena, the concept of damage velocity was introduced. Furthermore, a calibre independent representation of the results was found. The fracture and damage velocities in optical glasses with wave speeds between 4500 m/s and 6000 m/s and densities in the range from 2.5 g/cbcm to 5.2 g/cbcm were determined and compared to the results with float glass.