Determination of mechanical properties of PVC foam using a modified Arcan fixture

The design and development of a modified Arcan fixture (MAF) is described. The purpose of the fixture is to characterise polymer foam materials with respect to their tensile, compressive, shear and bidirectional mechanical properties. The MAF enables the application of pure compression or high compression to shear bidirectional loading conditions that is not possible with conventional Arcan fixtures. The tensile and shear behaviour to failure of a cross-linked Divinycell H100 PVC foam core material are studied using Digital Image Correlation (DIC). A detailed investigation of the parasitic effects of the fixture and misalignment of the fixture and loading machine are discussed. Thermoelastic Stress Analysis (TSA) is used to directly examine and validate the uniformity and symmetry of the stress fields obtained for both tensile and shear specimens. To account for the inhomogeneity of the strain field across the specimen cross sections, a “correction factor” for the measured “gauge section” surface strains has been determined using nonlinear finite element analysis (FEA). The outcome is a set of validated mechanical properties that are in excellent agreement with material property measurements conducted using conventional test tensile and shear test fixtures.