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In the next decade ceramic composites will increasingly be used as high-temperature components in advanced gas turbines. Ceramic components will allow an increase in the operating temperature of the gas stream (measured by the turbine entry temperature), thereby resulting in greater fuel economy in aerospace and automotive turbine applications. Since these materials will be produced from abundant nonstrategic materials, computational structural mechanics methods are evolving to keep pace with this technology. As a result, establishing protocols for sound design methodology, which is the subject of this technical note, is the focus of much current analytical research.

Our objective was to extend a reliability model proposed by Duffy and Manderscheid (1989) for orthotropic ceramic composites. Their approach used tensorial invariant theory to develop an integrity basis from which a subset of invariants was created to incorporate material anisotropy. Herein we propose a different subset of the original integrity basis and construct a more general scalar failure function. The assumption that the failure of a component is governed by its weakest link leads to a formulation that is similar in nature to the principle of independent action (PIA) model for monolithic ceramics. Note that this is a continuum approach to reliability analysis in that it excludes any detailed interaction between individual constituents.


Prepared for Lewis Research Center, under Cooperative Agreement NCC3-89 and Grant NAG3-862 IW A, National Aeronautics and Space Administration.