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Role of Porosity in the Effect of Microcracking on the Thermal Conductivity of Brittle Ceramic Composites

  • L. D. Bentsen
  • D. P. H. Hasselman

Abstract

Fracture-mechanical principles were used to predict the role of porosity in the formation of microcracks in brittle ceramic composites containing a dispersed phase with a coefficient of thermal expansion less than that of the matrix. It is shown that microcracking will occur only if the amount of porosity lies within a region Pi<P<Pa, and that all the microcracks will be of equal size. Using this criterion, the effect of the microcracks and pores on the thermal conductivity is examined. The expected behavior includes a sharp drop in the relative thermal conductivity and diffusivity at Pi, followed by a porosity-independent value between Pi and Pa. These conclusions were confirmed by measurements of the thermal diffusivity of composites containing silicon carbide dispersed in a matrix of magnesium oxide, beryllium oxide, and aluminum oxide, each with a range of compositions and amounts of porosity.

Keywords

Thermal Conductivity Stress Intensity Factor Thermal Diffusivity Silicon Carbide Crack Size 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Purdue Research Foundation 1985

Authors and Affiliations

  • L. D. Bentsen
    • 1
  • D. P. H. Hasselman
    • 1
  1. 1.Department of Materials EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgUSA

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