Integrated design and additive manufacturing of lattice-filled multi-cell tubes

In this paper, 3D printed lattice-filled multi-cell tubes, fabricated using chopped carbon-fiber-reinforced polyamide, were proposed to modify the deformation modes and improve the crashworthiness. Compression responses and energy absorption characteristics of the multi-cell tubes were investigated by quasi-static compression tests. The deformation and synergistic effect mechanisms of lattice-filled tubes were studied by observing the longitudinal sections of specimens. It was found that filling the lattice into multi-cell tubes exhibited an increase in the number of folds. When the lattice-filled tubes were fabricated integrally, multi-cell tubes changed from an asymmetrical to a symmetrical folding deformation mode due to the stronger and symmetrical interactions from the internal-filled lattice. Under the influence of the synergistic effect, the total energy absorption of the lattice-filled tubes with two different combination strategies presented increases of 55.6% and 83.8% compared with the sum of the empty multi-cell tube and pure lattice. In addition, a theoretical analysis for the mean crushing force of composite lattice-filled tubes was conducted based on simplified super folding element (SSFE) theory and bending deformation mechanism of the struts. The theoretical results were in good agreement with experimental studies and could be extended for lattice-filled tubes with other different filling configurations.