| Abstract: | Because of the nonhomogeneous morphology of rigid structural foams, the elastic moduli determined from tension and bend tests are different, the latter being larger. These moduli also depend on the geometry of the specimen. In general, the elastic bending stiffness of foams is determined by the rigidity tensor, which combines geometry and material information. Although the bending problem for nonhomogeneous materials is more complex than the equivalent homogeneous problem, the analysis simplifies considerably for thin-walled beams. The effective flexural modulus for a thin-walled foam beam is shown to be the tension modulus that would be measured on a flat foam specimen of the same thickness. The flexural modulus measured by bend tests on flat bars is shown to have very little effect on the stiffness of most thin-walled sections. This conclusion is independent of how the “true” material modulus varies across the thickness of the foam part. |
