Microstructural engineering of ceramic-matrix layered composites: Effect of grain-size dispersion on single-phase ceramic strength

A failure model is considered which can be applied to n-phase brittle mater ials (in particular to ceramics). The authors attempt to solve a physical p roblem of the description of failure of a micro-inhomogeneous solid as stoc hastic process of the cracking of separate structural elements. The particu lar model is executed for n=l (case of single-phase ceramics) and is applie d for the description of the mechanical behaviour of single-phase ceramic l ayers with various statistical distributions of the grains sizes. An effect ive continuum and a statistical description of the failure process is used. There are four stages in the process. The first stage is loading without m icrocracking and the second stage is a stable non-localized microcracking b efore maximum stress. The third stage is a stable localized microcracking a fter stress maximum and the fourth stage is an unstable (catastrophic) frac ture. The trends of the theoretical calculations agree with data obtained f rom acoustic emission studies. (C) 1999 Elsevier Science Ltd. All rights re served.