Quantitative estimation of material properties of porous ceramics by means of composite micromechanics and ultrasonic velocity

This paper describes a nondestructive method for the quantitative estimation of property variations due to porosity in advanced ceramics, The method employs a composite micromechanics which accounts for the effective density and elastic stiffness of a porous composite medium with a measurement of ultrasonic velocity. When the measured velocity is coupled with the theoretically predicted velocity, the unknown pore volume fraction is solved, from which other material properties are determined. The micromechanics model based on the Mori-Tanaka theory can handle ellipsoidal pores with a certain orientation distribution. Given the zero-porosity matrix moduli and the pore aspect ratio, the oblate spheroidal theory is first applied to hot pressed silicon carbide (SiC) samples in the range of about 85-100% of theoretical density and then extended to sintered samples in the density range of 93.6-97.6%. It is shown that the bulk density and elastic modulus of porous ceramics can be estimated accurately by the proposed method. Copyright (C) 1996 Elsevier Science Ltd.