Glass damage by impact spallation

This paper presents an investigation of spallation in impact-loaded glass. For this purpose, spall tests on cylindrical specimens were performed for various impact velocities using a Hopkinson bar “HB”. After each test, the specimen was rebuilt from restored fragments and the analysis of the fracture surface was performed by means of a scanning electron microscope. Fracture is found to propagate in a transversal way. In addition, numerical modeling allowed an appropriate prediction of the experimental stress level, time to fracture and fracture location. Based on microscopic observations of the fractured surface, a new fracture criterion has been proposed. It defines the damage variable as a function of the ratio between the initial surface and its evolution.