Effect of porosity on the thermal expansion coefficient of porous materials

The effect of porosity on the thermal expansion coefficient of porous materials is studied for two different cases. The first case concerns the thermo-elastic evolution of the porosity of a given material for which it is shown that the drained thermal expansion coefficients increase with the porosity increase. The second case concerns porous materials with similar solid phase and different porosity which is studied using the homogenization method. A parametric study shows the coupled effect of the thermal expansions and bulk moduli of the solid constituents on the thermal expansion coefficient-porosity relationship. Depending on the combination of the parameters, the thermal expansion coefficient can increase or decrease with the porosity. The effective thermal expansion increases with the porosity when a solid constituent has higher thermal expansion but lower rigidity than the other constituent. Generally, there is no unique thermal expansion-porosity relationship that can be applied to all porous materials.