Mechanical properties of porous materials

Abstract

Porous materials are commonly found in nature and as industrial materials such as wood, carbon, foams, ceramics and bricks. In order to use them effectively, their mechanical properties must be understood in relation to their micro-structures. This paper studies the mechanical properties of a few common porous materials: carbon rods, ceramics, polymeric foams and bricks. The characterisation of pore structures was performed using a Mercury Porosimeter. Detailed information was obtained on the density, porosity, surface area and pore size distribution. A large number of experiments on either bending or compression were conducted in order to obtain their macro-mechanical properties such as Young's modulus, hardness and strength. Based on the experimental observations, theoretical models were employed to predict the macro-properties from the micromechanics viewpoint. By studying the deformation of pores the global behaviour was calculated. Two simple formulae for the elastic modulus, E, were proposed: for low values of porosity, φ, E = E0(1 − 2φ) (1 + 4φ2) where E0 is the elastic modulus when the porosity is zero; for high value of porosity such as for foams E = E0 (1 − φ)2. The theoretical results agreed well with the experimental ones. The study has provided insights into the mechanical properties of porous materials over a wide range of porosity values.