Theoretical, numerical, and experimental study on laterally variable thickness (LVT) multi-cell tubes for crashworthiness

As a relatively new sectional configuration with a higher efficiency of material utilization, laterally variable thickness (LVT) structure has demonstrated its compelling features in energy absorption. To explore the crushing behavior of LVT multi-cell tubes as well as validate the corresponding finite element (FE) models and analytical solution for the mean crushing force, the quasi-static axial crushing experiments are first performed for the five-cell and nine-cell LVT tubes in this study. The FE models of LVT tubes are then created for investigating the crashworthiness of these structures; and the simulation results are found to agree well with the experimental data. Following the validated FE models, a parametric study is carried out to quantify the influence of the thickness gradient on the crashworthiness of the LVT tubes with the same mass as the uniform thickness (UT) counterparts. The results show that the LVT multi-cell tubes are of certain advantages over the uniform counterparts to be an energy absorber. Based on Super Folding Element (SFE) theory, the analytical models for the mean crushing force (MCF) and energy dissipation of the LVT multi-cell square tubes have been established with regard to the thickness gradient. The analysis is also performed to explore the mechanism of energy absorption enhancement by the evolution of theoretical models. It is confirmed that the derived analytical solutions provide give fairly good prediction of the mean crushing force and energy absorption of LVT multi-cell tubes.