THERMAL-SHOCK BEHAVIOR OF CERAMICS AND CERAMIC COMPOSITES

Tremendous efforts have been devoted to the studies of ceramic materia ls under transient thermal conditions over the past four decades. Such studies are becoming increasingly more important as advanced ceramic materials are demanded for applications at higher temperatures and mor e severe transient thermal conditions. In this paper, the theoretical and experimental studies on the thermal shock behaviour of monolithic ceramics and ceramic composites are reviewed; a survey of the experime ntal techniques that have been developed for characterising thermal sh ock damage is also included. It is shown that such studies for the mon olithic ceramics have been extensive. The theoretical analyses are bas ed primarily on the behaviour of monolithic ceramics and have been suc cessfully applied to explain experimental phenomena and predict the th ermal shock behaviour of monolithic ceramics. However, similar studies of the thermal shock resistance of ceramic composites, especially con tinuous fibre reinforced composites, are limited, despite the recent r apid advancements in ceramic composites and their improved properties. Fibre reinforced ceramic composites exhibit superior resistance to th ermal shock damage compared with monolithic ceramics. Catastrophic fai lure induced by severe thermal stresses can be prevented in ceramic co mposites. The theories developed for the monolithic ceramics can not b e applied directly to fibre reinforced ceramic composites because of s uch characteristics as anisotropy and mismatch of fibre and matrix pro perties. Although the water quench technique has been the most popular for thermal shock studies because of its simplicity, the fast heating technique with controlled power supply to the heat source offers a de sirable option. Both destructive and non-destructive techniques have b een used for assessing the thermal shock damage in a ceramic body, but non-destructive tests have the potential for application to engineeri ng scale ceramic components.