Fracture Resistance of Ceramics: Direct Measurements

Fracture resistance of ceramics is evaluated by flaking off the specimen edge and chip scar surfaces are examined. The fracture resistance characteristic was calculated from the results of direct measurements that did not make use of linear fracture mechanics concepts, which is typical of conventional fracture toughness test methods. A fracture resistance test method termed the edge fracture (EF) method is discussed. This method is built upon measuring the flaking resistance FR on indentation of the specimen. The FR values for homogeneous elastic ceramics are proportional to the KIc ones determined by the SEVNB method. Flaking resistance vs chip size relationships (R-lines) are derived. Data analysis was built upon statistically reliable measurements on advanced alumina, zirconia, scandia, and silicon nitride ceramics.