Parametric design of multi-cell thin-walled structures for improved crashworthiness with stable progressive buckling mode

Thin-walled single and multi-cell structures are an ongoing topic of interest in the field of crashworthiness, due to their wide range of applications in automotive and aerospace industry as lightweight energy-absorbing structures in crash environments. This work presents a new five-cell cross-section that merges high performance multi-cell and twelve-edge cross-sections from previous research, and compares its performance to four- and nine-cell square cross-sections. Super Folding Element (SFE) theory and Finite Element Analysis (FEA) in LS-DYNA are used to analyze cross-sections and found to have good agreement. The LS-DYNA environment is validated with physical testing. The geometry of the cross-sections is varied in order to find maximal values of the performance parameters specific energy absorption (SEA) and crush force efficiency (CFE) under stable progressive buckling mode and constraints for manufacturability. The nine- and five-cell cross-sections ultimately out-perform the four-cell cross-section, with the nine-cell having the highest SEA and CFE, though the five-cell design has a significantly lower (47%) mean crush force (Pm) for only an 11% and 14% loss in SEA and CFE respectively. As a final refinement, the geometry was varied across these two high-performing cross-sections to create equivalent mean crush forces to the four-cell cross-section, which showed the five-cell cross-section to have an improved SEA and better mass efficiency over the nine-cell under a mean crush force constraint.