Axial crushing response of novel toothed gear bio-inspired 3D printed energy absorbing structures

The conventional hollow cylindrical energy absorbing structure continues to face issues due to its relatively heavier weight, resulting in a very high initial peak load during crushing, hence, lowering its overall crushing performance. To address this challenge, this paper presents a novel bio-inspired cylindrical energy absorber by introducing toothed gears to the outer part of the hollow cylindrical structure, thereby, optimising it. The novel toothed gear bio-inspired cylindrical structures (TGBCS) are additively manufactured and made from six different polymer-based materials. These TGBCS are designed to mimic the gear-like profiles and the energy absorbing capabilities in the hind legs of the issus coleoptratus insect. The TGBCS are axially compressed under quasi-static loading condition and their crashworthiness performance are investigated experimentally, numerically and analytically. Composite-like deformation mechanisms are produced by the TGBCS which lead to improved load bearing and energy absorption capacities compared to their conventional types. The results also indicate that the TGBCS made from poly-lactic acid produce the best overall crushing performance in terms of specific energy absorption (SEA), mean crushing load (MCL) and crush load efficiency (CLE). Numerical investigation further reveals that SEA and CLE of TGBCS are approximately 52.54 % and 12.80 % higher than those of the conventional hollow cylindrical structures, respectively. Also, by correct choice of shape-topological modification of the TGBCS, it is observed that SEA can be significantly improved. Moreover, by using the simplified super folding element theory, the composite-like deformation mechanism of the TGBCS is adopted to formulate the mean crushing load.