On optimizing crash energy and load-bearing capacity in cellular structures

The energy absorption and load-bearing capacity under axial compression of some model cellular structures are studied with an eye toward optimization based on structural mass or volume available for deformation. Three configurations are considered: multilayer, multi-cell and multi-tube, all of a rectangular-cell topology. Loading is applied either parallel or normal to the cell axis. The cell’s aspect ratio and the relative density of the material ρ are systematically varied. The specimens are laterally confined by rigid walls to stabilize the deformation, but the effect of confinement diminishes for sufficiently large number of cells. A square-cell topology seems to be optimal. Together with an appropriate value for ρ, this provides an optimal constraint on the wavelength of the characteristic buckle and consequently extensive energy dissipation throughout the material body. When considering mean stress, crush energy and stroke or densification strain on the basis of minimum mass and volume simultaneously, ρ ≈ 0.5 seem to be a viable compromise among conflicting trends. The mechanical performance in this case is considerably improved over common cellular structures, for which ρ is typically <0.1.