Ambient and Elevated Temperature Fatigue Crack Growth in Ceramics and Ceramic Composites

Abstract

This paper examines the mechanisms of ambient and elevated temperature fatigue crack growth in ceramic materials under cyclic compression and cyclic tension loading conditions. The paper is divided into two parts. In Part I, we examine the origin and salient features of stable Mode I fatigue crack growth from stress concentrations in a wide range of ceramic materials subject to cyclic compression. Results of experiments and analyses for ambient and elevated temperature failure are discussed for polycrystalline Al2O3, Si3N4, MgO-PSZ, Y2O3-TZP, as well as SiC whisker-reinforced Al2O3 and Si3N4. In Part II, we discuss the mechanisms of constant and variable amplitude tensile fatigue crack growth in ceramics and ceramic composites. New experimental results of crack growth rates and detailed transmission electron microscopy observations of crack-tip damage in an Al2O3-SiC composite subject to tension fatigue at 1400°C are presented. Mechanisms of fatigue crack closure in both compression and tension fatigue are briefly outlined. The fatigue characteristics of ceramic materials are compared and contrasted with those of metals in an attempt to develop an overall mechanistic perspective on cyclic load damage.