Experimental study on the crashworthiness performance of rectangular and square tubes with and without bio-inspired ribs

Rectangular and square tubes, with and without bio-inspired ribs modelled on horse hoof wall microstructure, were experimentally evaluated for crashworthiness. The addition of ribs increased both the peak crush load (PCL) and energy absorption (EA); however, it reduced specific energy absorption (SEA) because of the added mass and spot-weld fractures caused by lobe-wavelength mismatch. This highlights a fundamental trade-off in bio-inspired designs. Spot welding proved ineffective for attaching the ribs and actually reduced the overall crushing resistance. Compared with square STR3_i tubes, the rectangular RTR_i tubes had 22% lower average mass and PCL, together with an 13.7% higher crush load ratio (CLR) and 20% higher SEA. The CRITIC-EDAS method prioritised low PCL and high SEA to identify optimal tubes for scenario-specific applications. A friction-inclusive theoretical model, based on established energy-balance principles, accurately predicted mean crush loads for top performers, validated against experiments.