Macro to Micro Stress and Strain Conversion in Porous Ceramics

Abstract

In this work, we propose an analytical model, capable of distinguishing the contribution of porosity, pore morphology and solid domain properties to the macroscopic elasticity of a porous ceramic material. A practical method is shown for the evaluation of the dense material elastic properties in porous (and microcracked) polycrystalline materials, making use of in-situ neutron diffraction experiments. By this method, axial and transverse microstrains measurements can reveal the average values for Young’s modulus and Poisson’s ratio of the dense material, as well as the value of pore morphology at known porosity. The approach has been validated on porous SiC. Finite Element Modeling is shown to allow calculating the three-dimensional strain and stress state under applied uniaxial stress, highlighting that small but finite shear stresses arise. Stress-strain curves of porous and microcracked materials have been generated, which correlate qualitatively well with the measured properties and can be used for quantitative numerical simulation of the materials strength. Predictions of FEM coincide very well with analytical calculations, thus corroborating the validity of the analytical method proposed.