A new multiaxial loading test for investigating the mechanical behaviour of polymers

In order to investigate polymer mechanical behaviour more closely and define corresponding numerical behaviour models, a new experimental set-up was developed for performing multiaxial loading tests. Some of the loading possibilities are presented here for the case of a copolymer polypropylene (PPC7712). A single moulded sample of this material was mounted on this original apparatus, which was specially designed for studying complex trajectories, including proportional and non-proportional cycles, in which the axial and shear deformation can be simultaneously and independently controlled. Tension/compression/torsion tests were performed on the polypropylene material, spanning all four quadrants of the axial/torsional strain subspace. Under the conditions tested, the effect of strain history on the stress-strain response is hardly observed for this material. The qualitatively different behaviour observed depending on the strain path might be attributable to the asymmetry between the axial/torsional and tension/compression loads.