Jafar Rouzegar - Department of Aerospace and Mechanical Engineering, Shiraz University Of Technology, P.O. Box
Abbas Niknejad - Mechanical Engineering Department, Faculty of Engineering, Yasouj University,
Seyed Mohammad Elahi - Department of Aerospace and Mechanical Engineering, Shiraz University Of Technology,
Seyed Ali Elahi - Mechanical Engineering Department, Faculty of Engineering, University of Tehran, Tehran, Iran

This paper investigates the effects of diameter and side length of metal and composite circular tubes and square columns under lateral compression on the amount of energy absorption capacities to find the optimum dimensions of energy absorbers. For this purpose some empty and polyurethane foam-filled specimens with different cross-sections and materials are tested and the results are compared with each other. Two kinds of polyurethane foam (called type 1 and type 2) were used for filled specimens. Polyurethane foam type 1 has higher density than type 2. Investigations on empty tubes showed that by increasing the diameter and side length, the SAE decreased. Also, investigations on filled tubes showed that for specimens filled by high density foam, by increasing diameter or side length up to a certain value, the specific absorbed energy increased, considerably. But by increasing the diameter or the side length after that, the specific absorbed energy remained almost constant or started to decrease. For square specimens filled by low density polyurethane foam, like empty specimens, SAE decreased by increasing side length.