From foams to girders - Towards a taxonomy for structured materials

Foams are structured materials. But, so as to simplify analysis, they are treated as homogeneous materials wherever possible. As the number of cells in the foam decreases the foam increasingly behaves like a structure. By seeking a description of both types of structure it should be possible to establish a unified model of structural efficiency through design parameters (load factor, material index, shape factor or relative density). This paper seeks to unify the quantities that measure the structural efficiency independent of the whether the structure is multi-cellular or uni-cellular. It is shown that the shape factor for simple structures is closely related to relative density for cellular structures.