Experimental and numerical crushing performance of crash boxes filled with re-entrant and anti-tetrachiral auxetic structures

Crash box structures are used for mitigating the transfer of impact sourced loads to the vehicle cabinet to prevent injuries and casualties. They are designed in the shape of tubes, and during loading, they can be depleted as sacrificial structures. For increasing energy absorption capability, particular types of fillers can be used in crash boxes. In the present study, the outcome of two particular filling structures on the energy absorption capability of crash boxes is investigated experimentally and numerically. As filling materials, PolyJet printed polymer re-entrant and anti-tetrachiral structures are utilized to investigate the effect of two main auxetic mechanisms of re-entrant and chiral. The crash boxes made of empty, re-entrant and anti-tetrachiral filled AA6063 square tubes are crushed experimentally under quasi-static conditions and numerical models are validated. Specific energy absorption (SEA) and crush force efficiency (CFE) are obtained for comparison to select the best configuration. The comparison of the SEA value of the anti-tetrachiral and re-entrant lattices filled tubes over the empty tube shows 28.5% and 20.6% improvements, respectively, while a similar trend in CFE with improvements of 50.6% and 40.27% for lattices are experienced, in the same sequence.