A method to distinguish extrinsic and intrinsic fracture-origin populations in monolithic ceramics

Fracture-stress data and fractographic examination for the identification of the fracture origin are presented for two types of brittle materials (tungsten carbide and silicon carbide (SiC)) tested either in three- or four-point bending. The results of the adjustment of a mixture of two Weibull distributions to the fracture-stress data through maximum likelihood estimates via R-software (version 1.8.1 2003, package MASS) agree quite well with the results of the fractographic examinations. Different flaw distributions (e.g. extrinsic and intrinsic) are observed, and each has its own strength distribution parameters.