The effect of cell size on the mechanical behavior of cellular materials

Abstract

The Young's modulus, strength and fracture toughness, of a brittle reticulated vitreous carbon foam, was measured as a function of cell size at a constant density and compared to a theoretical model. Image analysis was used to characterize the macrostructure of the samples and provided a basis for evaluating the mechanical behavior. It was determined that both the compressive and bend strength scale inversely with cell size. The change in compressive strength is due to a change in the strut strength with cell size. The bend strength behavior may be due to a reduction in the critical flaw size, as well as the increasing strut strength at smaller cell sizes. The fracture toughness and elastic modulus were found to be independent of cell size. Comparison of these results with previous work on open cell alumina clearly indicates a very different behavior and is attributed to a change in the microstructure of the solid phase with cell size in the alumina materials.