Experimental Study of the Mechanical Behavior of Polyvinyl Chloride Foam under Shear Stress

The development of modern technologies requires the use of materials with high mechanical properties specific to their use, but with low densities. Composite materials with sandwich structure meet the above requirements, due to their low density, high strength, high rigidity and excellent durability. Despite of their advantages, sandwich structure is rather sensitive to failure by shear load of the core. Previous work has shown that standard shear characterization tests of sandwich structure (ASTM C273, Standard Test Method for Shear Properties of Sandwich Core Materials) exhibit shear stress concentrations at the edges, which negatively affect the results and validity of this test. To solve this issue, this research work aims to propose a new test methodology to determine shear properties using a torsion test. A custom assembly has been developed to exert a torsional moment on a cylindrical specimen made of PVC foam. Based on the experimental results, this new test approach for shear properties of Divinycell H200 provides more accurate characterization than the standard test by eliminating the phenomenon of concentration of shear stresses at the edge. Under shear fatigue test, the dominant failure mechanisms were the buckling of cell walls, which enhanced the strain and reduced the foam strength.