Comparative analysis of the mechanical behavior and plastic deformation of empty and polyurethane foam-filled polyethylene tubes under lateral compression

In this research, the energy absorption and plastic deformation of circular polyethylene tubes under lateral compression were investigated, comparing empty tubes with those filled with polyurethane foam. The effects of tube length, diameter, wall thickness, and filler density on load-bearing capacity and energy absorption were evaluated. Absorbed energy and lateral load were found to increase with tube length, although the ductile response of polyethylene produced pronounced fluctuations in the load-displacement curve. Diameter influenced the two configurations differently: in empty tubes, smaller diameters yielded greater energy absorption, whereas in foam-filled tubes, larger diameters increased the flattening load and total absorbed energy, underscoring the critical role of diameter in foam-filled systems. Increasing wall thickness enhanced energy absorption, but polyurethane-foam filling was more effective and yielded a more consistent, predictable load-displacement response. Foam-filled tubes outperformed empty tubes overall; dominant damage mechanisms were identified as foam fracture, crushing, and densification. For applications prioritizing structural efficiency and specific absorbed energy (SAE), the use of higher-density polyurethane foam is recommended. Adhesion between the foam and the tube's inner surface significantly increased peak load capacity. After relaxation, a uniform diameter reduction of approximately 12.7% was observed across specimens, indicating consistency in the final morphology. These findings provide guidance for the design of load-bearing systems employing polyethylene tubes and polyurethane foam.