Dependence of ceramics fracture properties on porosity - Comment

Wagh, Poeppel and Singh developed a 'connected-grain' model for describing the porosity dependence of modulus of elasticity in ceramics. They derived the relation E(p) = E 0 (1 - p) m where E(p) was the effective modulus of elasticity of a porous material, p was the volume fraction of porosity, E 0 was the modulus of the same material after full densification, and exponent m depended on the tortuosity of structure. It had a value of nearly 2 for sintered ceramics. In a later paper, relations were derived from the same postulates for other mechanical properties. The present paper shows a mistake in the derivations.