Mechanics and mechanisms of toughening of advanced ceramics

Abstract

In addition to toughening induced by phase transformation, crack deflection and bridging, near-tip microcracking has been identified as being another important source of toughening of advanced ceramics. In this paper, attention is devoted to the examination and modelling of these toughening mechanisms using an appropriate discrete damage model in which the microcracking region is modelled as a zone containing discrete multiple microcracks interacting with a main crack. These interaction effects between a main crack and microcracks have been studied by a number of researchers; existing solutions, however, suffer from certain difficulties resulting from over simplifying the problem. We have recently obtained a general explicit solution to the corresponding antiplane and plane problems of an arbitrarily located and oriented elliptical hole in the vicinity of the main crack under generalized loading conditions. Two aspects of the current problem are examined. The first is concerned with shielding and amplification effects associated with the release of uniform or non-uniform residual stresses from a single microcrack, while the second is concerned with shielding effects associated with the formation of a microcracking region around a stationary and a steadily growing main crack.