Strain localization and cyclic damage of polyurethane foam cylinders: experimental tests and theoretical model

International audienceUniaxial compression tests performed by the authors on polyurethane foam cylinders show the typical stress-strain response curve of cellular materials, consisting of two ascending branches, separated by an almost horizontal plateau in which strain localization is observed. With less evidence, the same three regimes appear at unloading. Under cyclic deformation there is a progressive decay of the loading curve, while the unloading curve remains essentially the same at all cycles. To describe this complex response we propose a rheological model, in which the foam is represented as a chain of nonlinear elastic springs with a non-convex strain energy, connected in parallel with a series of springs subject to progressive damage. The chain of springs models the strain localization, and the second series of springs reproduces the cyclic response. The overall stress-strain behavior of the model is in a good qualitative agreement with the experiments