Multi-axial Mechanical Properties Test Of Energy-absorbing Polyurethane Foam

During the vehicle crash, how to protect the passengers and reduce the pedestrian damage have become the focus in the field of automobile safety. Polyurethane foam is one of the important materials in automotive interior and exterior assembly, due to their light weight and high energy absorption capability. It is the most important to study the mechanical properties of the polyurethane foam in its design process. Some tests, including uni-axial tension, uni-axial compression, shear test and hydrostatic compression, were conducted to investigate the multi-axial mechanical properties of PU(polyurethane) foam under different loading conditions, different densities and different strain rates. The main works to be carried out are given as the following:(1) In uniaxial compression test, densities and the strain rates can influence the mechanical property of polyurethane foam, such as Young’s modulus, energy absorption and energy absorption efficiency. The Poisson’s ratio of the polyurethane foam is proportional to its density. SEM test shows that when foams are subjected to the compressive load, its cell wall ruptures, but the cell wall pillar remaines almost intact.(2) In the tensile test, polyurethane foam shows fracture of brittle properties. The Density of polyurethane foam and the strain rate show the proportional relationship with the elastic modulus of foam, breaking strength increases with the density of foam, but the strain rates has a little effect on the fracture strength of foam.(3) In the shear test, the apparatus structure and specimens have been optimized. The density is an important factor that affected the mechanical properties of polyurethane foam; With the increase of the density, the shear modulus and shear strength will increase correspondingly. SEM test proved that polyurethane foam shows brittle property when subjecting to the shear load.(4) In the multi-axial compression test, density and confining pressure size can influence the performance of polyurethane foams. The fluctuation of stress-strain curve was related with the bearing load of the foam during the test. The microscopic deformation of foam cell is different when the confining pressure changes. The deformation degree of foam increases with the confining pressure, and the deformation degree in the lateral direction is more serious than that in the longitudinal direction.