Quasi-static behavior identification of polyurethane foam using a memory integer model and the difference-forces method

Flexible polyurethane foam is widely used in numerous comfort applications such as automotive seat cushions and mattresses. It would be interesting to design a mechanical model which describes the behavior of this material in a series of test conditions. This study is devoted to the modeling of the quasi-static behavior of polyurethane foam using a memory integer model. Polyurethane foam undergoing large compressive deformation exhibits highly nonlinear elasticity and a viscoelastic behavior. The memory integer model describes the nonlinearity in a polynomial function and the viscoelasticity through a convolution function. Uniaxial compression tests help to identify the mechanical parameters of the model. The difference between the force responses of foam in load and unload phases constitute the base element of the method used in this article. Numerous precautions are taken into account to obtain accurate results which verify the thermodynamic conditions. Finally, the reliability as well as the limits of the memory integer model are discussed.