Absorbed energy by foam-filled quadrangle tubes during the crushing process by considering the interaction effects

In this article, some theoretical relations are derived to predict instantaneous crushing force and absorbed energy during initial fold formation in polyurethane foam-filled quadrangle tubes under the axial crushing load. Theoretical analysis is performed based on the energy method. In the theoretical analysis, crushing wavelength is considered as a constant parameter through the process and as a function of column geometrical dimensions. In the analytical calculations, interaction effects between the polyurethane foam and inner wall of quadrangle tubes are considered and a formula is presented to predict absorbed energy by the interaction effects. In the experiment part, some foam-filled specimens were prepared and axially crushed to obtain experimental diagram of crushing force versus axial displacement. Comparison of the theoretical predictions of crushing force and absorbed energy with corresponding experimental results showed a good agreement. Also, it was found that theoretical predictions by considering the interaction effects have a better correlation respect to the experiments.