Effects of cell size and cell wall thickness variations on the strength of closed-cell foams

In this work, the effects of cell size and cell wall thickness variations on the compressive and shear strengths of closed-cell foams were investigated using Laguerre tessellation models. It is found that the compressive and shear strengths of closed-cell foams decrease as cell size and cell wall thickness variations increase, and the compressive strength reduces more significantly. At a given level of variation, the effect of cell size variation on strength reduction is comparable to that of cell wall thickness variation on them. In the foam studied (M130 foam), cell wall thickness has a larger dispersion than cell size, and therefore is the main contributor to the strength reduction of the foam. In comparison to compressive and shear stiffnesses, cell size and cell wall thickness variations reduce compressive and shear strengths more significantly. Cell size variation results in strain concentration at the end of foam samples, thereby reducing the compressive strength of closed-cell foams. Cell wall thickness variation leads to cell wall buckling and thus reduction in compressive and shear strengths of closed-cell foams. As cell size and cell wall thickness in foams become less uniform, the relationships of compressive and shear strengths to relative density become less linear.