Enhancing crashworthiness of body-centred cubic lattices using bio-inspired hierarchical reinforcement

The advent of additive manufacturing has thrust lattice structures to the forefront with potential applications in energy absorption and light weighting. In this context, bio-inspired structures are gaining popularity, especially due to their unique hierarchical architecture, which often exhibits remarkable mechanical properties. In this study, a novel vertex hierarchical structure inspired by beetle forewing microstructure is proposed, and its energy absorption properties are numerically analysed. The crashworthiness metrics were calculated for the force vs displacement response of each lattice structure and compared. The stiffness values of the first-stage were found to be sensitive to the strut diameter, while the second-stage stiffness showed dependence on sub-cell geometry. Among the hierarchical lattices, the body-centred cubic with vertical struts (H-BCCZ) showed a 220% increase in specific energy absorption (SEA) and a 575% increase in mean crushing force (MCF) over the primitive body-centred cubic (BCC) structure. The hierarchical structures also displayed two distinct plateau regions, indicating multi-stage collapse. Furthermore, a parametric study was conducted for all lattices by varying the hierarchical length ratio (λ), and it was observed to significantly influence the stage-wise stroke length. Within the investigated design space, the hierarchical face-centred cubic lattice with Z-struts (H-FCCZ) with λ = 0.8 showed the best crashworthiness, providing a 100% enhancement in SEA compared to the traditional BCC structure of identical relative density.