COMPRESSIVE TESTING OF CERAMICS

Research has been conducted towards the development of a compressive t est method more suitable than present procedures for use on advanced c eramics with extremely high compressive strength. A dumb-bell-shaped s pecimen is proposed as an edge-effect-free shape, and test equipment w ith a self-aligned system is suggested to estimate accurately the comp ressive strength. Experimental results for some structural ceramics in dicate the following: (1) the columnar specimen prescribed in the Japa nese Industrial Standards has edge effects, whereas a dumb-bell-shaped specimen has no edge effect and shows higher strength than the column ar specimen; (2) acoustic emission events are detected at an early sta ge of the compressive load, and the behaviour coincides with the initi ation of the crack propagation under compression; (3) an isolated crac k on the specimen surface of ceramics with a fine matrix has little in fluence on compressive strength.