Dynamic axial crushing of short to long circular aluminium tubes with agglomerate cork filler

Cork is a complex natural cellular material with quite unknown or not well understood properties. It is available in the natural and in the agglomerate form and it is an ecological and very durable material. That is why it is used today as thermal and acoustic insulator, as a seal and as an energy-absorbing medium in flooring, shoes and packaging, among others. However, the application of agglomerate cork as filler inside structural thin-walled sections, in order to increase the energy absorption, has not been much explored. Dynamic experimental tests were carried out on empty and micro-agglomerate cork-filled tubes with 22 and 50 mm in internal diameter (D)(D) and length (L)(L), respectively, and numerical simulations were performed with the finite element method software LS-DYNATM, showing good agreement in terms of load–displacement curves and deformation patterns. Having validated the numerical model with experiments, the finite element model was used to undertake a systematic study of circular tubular structures impacted at 10 m/s. The load-deformation characteristics, energy-absorption response and collapse mode transitions of empty and cork-filled aluminium tubes with varying diameters and thicknesses (t), lengths of 25, 300 and 350 mm, but with constant slenderness ratios D/tD/t and D/LD/L were thus studied. Relevant comparisons were raised, showing that the slenderness ratios are very important parameters that globally govern the percentage increase in energy absorbed by tubular structures after cork-filling during an impact loading.