Modeling the impact of microcracking on the thermoelasticity of porous and microcracked ceramics

Abstract

The foundations of the Integrity Factor Model are laid down and the model is discussed. The calculation of the internal stresses in microcracked materials (as a function of temperature) is done on the basis of both the macroscopic dilation and the lattice expansion measured by diffraction. The derivation is made starting from first principles for a single crystal, and then extending the approach to polycrystals, including complex microstructures, such as those containing porosity, microcracks, and multiple phases. Focus is cast on the fundamentals of the relationship between material properties and microstructure of anisotropic crystals, and on the resulting macroscopic behavior. The model is validated against experimental data, with the examples of the microcracked β-eucryptite and porous microcracked aluminum titanate composite.

Keywords:

• integrity factor
• thermal expansion
• elastic modulus
• microcracking
• internal stress

Acknowledgements

Bryan Wheaton (Corning Incorporated) provided XRD data. Christine Heckle (Corning Incorporated) provided useful comments on the manuscript. Mark Kachanov (Tufts University) made important points, which were incorporated in the paper. Angela Graefe (Corning Incorporated) thoroughly proofread the manuscript and provided very valuable suggestions.