Probabilistic aspects of brittle fracture

Statistical treatments of local brittle fracture stress and fracture toughness are treated at three levels: the micro-scale, the macro-scale and the meso-scale. Developments of the RKR/Curry-Knott models and other forms of "local approaches" are set in the context of a need to estimate credible lower-bound properties for safety assessments. A comparison is made between Weibull analysis of data and the use of a Normal distribution. The dangers in using non-physically-based extrapolation of data for spatially "heterogeneous" materials are explained and guidelines for analysing such data are proposed. Application to the brittle fracture of silicon carbide and of optical fibres helps to clarify effects of variations in fracture stress, fracture toughness and "inherent" defect population.