Out-of-plane impact of a bio-inspired bidirectional gradient hierarchical triangular honeycomb structure

Inspired by the hierarchical distribution of canine osseous structures and the inherent stability of triangular configurations, this article introduces a novel bio-inspired bidirectional gradient hierarchical triangular honeycomb (HTH) structure. This design integrates hierarchical strategies within triangular structures, founded upon a hexagonal framework. By manipulating the dimensions of the inner hexagon, two distinct configurations are developed: the hierarchical equilateral triangular honeycomb (HETH) and the HTH. Experimental methodologies are employed to validate the established finite element model. Subsequently, this verified model is utilized to systematically investigate the effects of parameters such as hierarchy and triangular geometry on structural performance. The findings reveal that, under equivalent wall thickness conditions, structures with higher hierarchical configurations exhibit superior crashworthiness. Specifically, HETH-3 demonstrates enhancements of 1326% in energy absorption (EA), 300% in specific energy absorption (SEA), 256% in initial peak crushing force (IPCF), and 301% in crushing force efficiency (CFE), when compared to HETH-0. Similarly, HTH-3 displays improvements of 1181% in EA, 254% in SEA, 261% in IPCF, and 255% in CFE relative to HTH-0. Under equivalent mass conditions, higher hierarchical structures also significantly outperform their lower counterparts. Furthermore, when compared to other conventional hierarchical honeycombs of the same mass, the SEA and CFE values of the vertex-based HTH (VBT) were only 79% of those of HETH-3, while the SEA and CFE of HTH-3 were 95% of HETH-3. The proposed bio-inspired bidirectional gradient HTH structure, informed by natural bone architecture, demonstrates enhanced crashworthiness, offering valuable insights for the design of lightweight 3D-printed honeycombs with exceptional mechanical properties.