Cyclic response of anisotropic polyurethane foam to multiple static and quasi-static loading tests

Studies on anisotropic mechanical behavior of polyurethane foams under cyclic compression remain limited. This work reports the cyclic compression response of an anisotropic rigid open-cell polyurethane foam (RPUF) tested along the foam rise direction (D1) and the transverse direction (D2), at three crosshead speeds (5, 50 and 500 mm/min), corresponding to nominal strain rates of 3.3 × 10 -3 , 3.3 × 10 -2 and 3.3 × 10 -1 s -1 for an initial thickness of 25 mm, and at three deformation amplitudes (10%, 50% and 80%). Quasi-static loading-unloading tests (20 cycles) were conducted to obtain stress–strain loops. The cycle-by-cycle evolution of the maximum compressive stress and the absorbed energy density was quantified, showing a progressive reduction of mechanical performance with cycling. Finally, two compact analytical relationships are proposed to model the evolution of maximum stress and absorbed energy as functions of cycle number and strain rate, in good agreement with the experimental trends.