Mechanical properties, modeling and design of porous clay ceramics

Porous ceramics with three different porosities were fabricated by the sintering of redart clay and woodchips (sawdust). The latter was used as the pore-forming agent in porous ceramic water. The porosity, pore size and density of the materials were characterized using Mercury Intrusion Porosimetry and Helium Pyncnometer technique, while the structure and chemistry of the materials were elucidated via X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM) and energy dispersive X-ray spectroscopy (EDX). The compressive strength of the porous clay ceramics were found to exhibit a downward trend with increasing porosity. Due to the anisotropic nature of the porous material, two types of specimen (T- and S-Type) were fabricated for the measurement of flexural strength, fracture toughness and resistance-curve behavior under three point bending. The observed crack-tip shielding/toughening mechanism was then modeled using fracture mechanics concepts. The measured mechanical/physical properties, such as: elastic modulus, density and porosity, were then incorporated into finite element models for the computation of stress distributions due to hydrostatic pressures exerted on the porous clay ceramics by the water in filter with different geometries and supporting configurations. The implications of the results are discussed for potential scale-up and design of a mechanically robust porous ceramic for water filtration.