Approaching ideal energy absorption through the multicellular structure with gradient material distribution

Energy absorption of traditional tubular energy absorbers is restricted by the low structure efficiency, which makes the mean crushing force of the structure usually much lower than its yield strength. The combination of a multicellular design and a gradient-thickness strategy significantly improves the energy-absorption ability of thin-walled energy absorbers while reducing weight. Gradient-thickness multicellular tubes (GTMT) were studied in this paper to demonstrate this advantage. Mechanical performances of GTMT with two material-distribution principles, sample gradient thickness (SGT) and modified gradient thickness (MGT), were investigated experimentally and numerically, primarily in terms of folding behaviors, energy-absorption ability, and load-carrying capacity undulation. Wire-cut electrical discharge machining technology was used to create a series of aluminum alloy specimens that were then compressed under quasistatic loading conditions. Following that, finite element method was used to run detailed numerical simulations. The effect of geometric configuration was determined after conducting parametric studies with different cell density and thickness gradient coefficients. The results showed that, compared to a traditional multicellular tube, a gradient-thickness one with MGT material distribution can improve structural efficiency with a stable loading history. Increases in cell density and thickness gradient coefficient have positive effects on energy-absorption ability; however, excessively high parameter values will lead to global bending deformation and weaken the mean crushing force. Therefore, reasonable parameter matching is vital. The result shows that when the cell density reached 9 × 9 and the thickness gradient coefficient reached 1.4, the mean crushing force was 98.16% of the full-plastic strength of the matrix, and there was no irregular deformation, indicating that ideal energy absorption is almost achieved. These achievements pave a way for achieving ideal energy absorption.