Theoretical and experimental studies of the instantaneous folding force of the polyurethane foam-filled square honeycombs

This paper presents a theoretical formula to predict the instantaneous folding force of a polyurethane foam-filled square column as a single unit of square honeycombs under axial loading. For this purpose, sum of the dissipated energy rate under folding deformations of the square column and the dissipated energy rate of polyurethane foam compression was equated to the work rate of the external force on the structure. The dissipated energy rate of compression and deformation of polyurethane foam was obtained by presenting a new deformation model and through the reduced volume ratio. The final formula obtained, reasonably predicts the instantaneous folding force of the polyurethane foam-filled square column. Finally, according to the calculated theoretical relation, the instantaneous folding force of the foam-filled square column was sketched versus the axial displacement and compared to the experimental results, which showed a good correlation.