Axial crushing of self-lock multi-cell tubes with foam filler and tube envelope

A type of self-lock multi-cell tubes assembled by open section components is recently proposed to serve as energy absorbing devices. Due to the open feature of the section, the self-lock tubes with large width may develop global buckling mode under axial crushing and show much worse energy absorption performances. To overcome this drawback, expanded polystyrene (EPS) foam fillers are firstly employed to improve the stability of the structural deformation and to increase the energy absorption efficiency. Experiment results show that a 4% increase in mass by EPS foam leads to about 20% increase in energy absorption of the self-lock tube. Numerical analyses are also carried out to simulate the tests and analyze the structures with other enhancement methods including Al foam filling and tube enveloping. They may be employed separately or simultaneously. The combination method of Al foam filling and tube enveloping gets the highest energy absorption capacity and efficiency. Theoretical analysis is performed to predict the mean crushing force of self-lock tubes enhanced by Al foam filling and tube enveloping, and the theoretical results compare well with numerical results. Finally, crashworthiness optimization problems are proposed and solved to explore the optimal enhancement configurations of the self-lock multi-cell tubes.