Criteria of ceramics fracture (edge chipping and fracture toughness tests)

Abstract The methods for evaluating the fracture resistance of ceramic and other brittle materials are discussed. It is shown that the edge-chipping test method may be considered competitive to the conventional methods based on linear elastic fracture mechanics. It allows testing small specimens. This makes it promising for the evaluation of biomedical ceramics and other materials used to manufacture small-sized products or materials from which it is technically difficult or expensive to make ordinary specimens. This energy method differs from the methods based on Griffith's ideas because it evaluates the fracture resistance of materials at all three stages of fracture: crack nucleation, initiation, and propagation. It is confirmed that the data points for ceramics are similar to those of the model material of linear elastic fracture mechanics group along a straight line (called the baseline) on the fracture resistance ( F R ) versus fracture toughness ( K Ic ) diagram (called the base diagram). This is due to the similarity of the fracture surfaces of the chip scars on the edges of specimens. It is shown that the test data of Mg–PSZ and other ceramics can also group along a straight line on the base diagram. It is established that the edge-chipping test methods fail to compare ceramics with dissimilar fracture surfaces of chip scars. The aforesaid is supported by the test data for different ceramic materials.