The porosity dependence of sound velocities in ceramic materials

Abstract

The porosity dependence of transverse and longitudinal sound wave velocities is studied in statistically isotropic porous ceramics. Based on the model relations for elastic moduli six model relations are constructed for the prediction of the porosity dependence of these velocities. All of them predict a decrease of sound wave velocities with increasing porosity, but the Maxwell / Mori-Tanaka / MMT model leads to unrealistic predictions for high porosity. A velocity ratio function is defined which contains the porosity dependence of the effective Poisson ratio and enables the prediction of longitudinal wave velocities. A comparison with literature data shows that most data lie below the exponential prediction and above the numerical prediction for concave pores. The correlation of the normalized longitudinal wave velocities and relative transverse wave velocities shows that essentially all values are above the highest lower bound and are reasonably predicted by the differential, exponential and self-consistent models.