Fractography and fracture mechanics property assessment of advanced structural ceramics

Fracture characteristics and mechanical properties of advanced structural ceramics produced by advanced technology and developed for high temperature applications are reviewed from the viewpoint of fractography. The main processing routes for preparation of in situ reinforced ceramic matrix composites, nanocomposites, and laminar/layered composites are summarised and their principal microstructure parameters are described. The main observation techniques, levels/steps of observation, and principal fracture mechanics relations are summarised. The relationships between rupture strength, Weibull modulus, and defect distribution, and the possibilities for strength improvement through improved processing, are discussed. Recent results relating to strength and reliability prediction are given. The fractographic appearances of process and bridging zone toughening mechanisms are described and the relationship between fracture toughness, microstructure, and fracture micromechanisms is discussed. Interfaces (macro- and microscale) and residual stresses and their effect on toughness, strength, and reliability of nano- and layered composites are analysed. The influence of loading mode on fracture and mechanisms leading to fatigue degradation in these materials is summarised. Fracture surface characteristics of high temperature crack growth and creep failure are described and the effects of oxidation and corrosive degradation on fracture and strength of these materials are considered. The role of fractography in the development of advanced ceramics and in efforts to improve reliability is described. (C) 1999 IoM Communications Ltd and ASM International.