Delayed failure in a shock-loaded silicon carbide

The shock response of a silicon carbide has been investigated using the methods of plate impact, and monitored using manganin stress gauges mounted so as to be responsive to lateral stress. Close to the impact face, a two-step stress response is observed, indicating the presence of delayed failure at the impact face. As the shock front moves through the target, the failure wave appears to slow, before arresting between 4 and 6 mm from the impact face. Measured shear stresses (ahead of the failure front) are in good agreement with the calculated elastic response, and with similar measurements made by both ourselves in other grades of silicon carbide and other authors. In gauge traces where the failure wave was not observed, a slight decrease in lateral stress (and thus a corresponding increase in shear strength) has been noticed. A similar response in some metals (in combination with recovery work in other ceramics) has led us to suggest that a degree of plastic deformation, in combination with a more brittle response, has occurred