Research on the dynamic mechanical properties of C-plane sapphire under impact loading

Sapphire is widely used as optical materials and substrate materials because of its excellent physical and chemical properties. The dynamic mechanical properties under impact loading are very important for the sapphire parts used in extreme conditions. In this study, the dynamic mechanical properties of C-plane sapphire have been tested on the Split Hopkinson Pressure Bar. The true stress-strain curve of sapphire has been obtained at different velocities. The failure process of sapphire has been observed via high-speed photography. And the fracture morphology of sapphire after impact was analyzed. It is found that sapphire undergoes a very small linear section under impact loading. Subsequently the microcrack damage evolution stage occurs and then crack propagation is instability after reaching the compressive limit. It is found that the impact velocity has no effect on the linear elastic section of sapphire, but the compressive strength and fracture of sapphire will increase with increasing impact velocity. The crystal orientation influences the crack path and crack pattern, which lead to different energy consumption during crack propagation.