Fractography and fracture mechanics property assessment of advanced structural ceramics

Fracture characteristics and mechanical properties of advanced structural c eramics produced by advanced technology and developed for high temperature applications are reviewed from the viewpoint of fractography. The main proc essing routes for preparation of in situ reinforced ceramic matrix composit es, nanocomposites, and laminar/layered composites are summarised and their principal microstructure parameters are described. The main observation te chniques, levels/steps of observation, and principal fracture mechanics rel ations are summarised. The relationships between rupture strength, Weibull modulus, and defect distribution, and the possibilities for strength improv ement through improved processing, are discussed. Recent results relating t o strength and reliability prediction are given. The fractographic appearan ces of process and bridging zone toughening mechanisms are described and th e relationship between fracture toughness, microstructure, and fracture mic romechanisms 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 fract ure and mechanisms leading to fatigue degradation in these materials is sum marised. 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 effort s to improve reliability is described. (C) 1999 IoM Communications Ltd and ASM International.