Theoretical evaluation of tensile and flexural moduli of structural polymer foams

Abstract

In this paper, the tensile and flexural behaviors of structural polymer foams with integrated skin layer are studied. Several models are reviewed to show the dependence of Young’s modulus of cellular solids on void fraction. Effective flexural modulus of structural foam is computed based on the Euler–Bernoulli beam theory and results are compared with experimental data available for uniform density core. The effects of skin thickness, core relative density, and density transition profile on the elastic modulus are investigated for symmetrical structural foams. Lower and upper bounds of effective moduli are obtained to evaluate the role of structural foams in increasing specific mechanical strength of polymeric structures. The optimum thickness of solid skin is then estimated in terms of relative density of cellular core to get maximum specific tensile or flexural modulus. Density profile of structural foams with graded density core is also optimized to find the most possible value of specific flexural modulus. The present study is expected to provide some useful information for evaluation and designing of structural foams with the aim of material saving and improvement in mechanical properties.