Laminate model expressing mechanical properties of polypropylene foams having non-uniform cell-shape distributions

The tensile and bending deformations of polypropylene (PP) foam manufactured by using an extruding process were investigated using a laminate model based on the measured distribution of cell sizes. Anisotropic cell shapes and cell-size distribution were found to depend on the extrusion direction based on cross sectional observations of PP foam. The laminate model with anisotropic cell shapes and a non-uniform cell-size distribution can account for the measured deformation in PP foam. Each layer in the laminate model was composed of the same-sized anisotropic cells. A comparison of theoretical and experimental results showed that the laminate model was good for evaluating the actual elastic moduli and strengths of tensile and bending deformations. Therefore, the cell-size distribution depending on the manufacturing process was found to be an important consideration when mathematically evaluating deformation of foam.