Elastic moduli of open-cell cordierite foams

The elastic moduli of open-cell cordierite foams were measured as a function of their relative densities by an impulse excitation method. The values of Young's modulus and shear modulus were found to be dependent upon both the relative density and the microstructure of the cell structure with the elastic moduli increasing with decreasing of porosity. The density exponent was found to be in reasonably good agreement with theoretical models that considered cell strut bending as a major deformation mode. The materials studied were found to contain closed cell faces, which seem to have an effect on the elastic behavior, particularly for foams with porosity lower than 80%. The values of Young's modulus (1-5 GPa) and the shear modulus (0.6-2.5 GPa) depended on the relative density in accordance to the available theoretical models. However, surprisingly very low Poisson's ratios were estimated suggesting that either the developed foams cannot be regarded as isotropic materials or the cellular architecture became re-entrant so that the cell struts protrude inward rather than outward. Also noted was that the Poisson's ratio was independent of the density of the cordierite foams (within the experimental errors and the density range investigated) which is consistent with the theoretical predictions.