Impact fracture behavior in alumina ceramic plates

In this study, a bar impact test of low velocity was carried out to gain an insight into the damage mechanism and sequence induced in alumina plates during quasi-static impact conditions. An experimental setup which could measure directly the impact force applied to the specimen and supply a compressive pre-stress to the specimen by utilizing an long bar impact was devised. During the bar impact testing, the influence of the pre-stress applied to the specimen along the impact direction on the fracture behavior was investigated. The measured impact force profiles explained well the damage behavior induced in alumina plates. The application of higher pre-stress to the specimen led to less damage due to the suppression of radial cracks which was caused by the increase in the apparent stiffness of the plate. The observed results showed the following sequence in damage development: The development of cone crack at the impact region, the formation of radial cracks from the rear surface of plate depending on the plate thickness, and the occurrence of crushing or fragmentation within the cone envelope.