Effect of Hierarchical Geometries Matching on the Crashworthiness of Honeycomb

Abstract

The demand for lightweight engineering structures to serve as structural components and energy absorbers has been on the rise in recent times. [1][2][3][4][5][6] As a typical engineering material, cellular structures have been extensively applied in several fields, including railway, [7] structural engineering, [8] aviation, [9] and biomedical field. [10] The application of cellular structures is attributed to specific desired properties, including lightweight, high energy absorption capacity, excellent impact resistance, and high strength-to-weight ratios. [11,12] Cellular structures take the form of either honeycomb (which is a two-dimensional array of identical prismatic cells that nest together to fill a plane) or foam (a polyhedral three-dimensional cell that packs together to fill space). [5] The mechanical properties and crashworthiness of cellular structures mainly depend on their geometric configuration and base material properties. [13,14] By taking advantage of the flexibility in geometric configurations, continuous research is being done on cellular structures with experimental, numerical, and theoretical approaches to achieve desired and tailorable mechanical properties. [15][16][17] These researches attempt to improve further the mechanical properties of the cellular structures for better and broader application scope. Consequently, some promising areas relating to cellular structures have been gaining lots of attention, including hierarchical cellular structures, [18][19][20][21] multicell tubes, [18,22] functionally graded structures, [23] corrugated tubes, [24] metamaterial structures, [25][26][27] multicornered structures, [28] and staggered cellular structure. [29] The development of industries toward more efficient performance has led to the continuous desire for improved lightweight and better energy absorption properties. Honeycombs with structural hierarchy have shown promising potential to offer excellent crashworthiness characteristics.Materials possessing structural hierarchy have been extensively observed in nature, [19,30] as can be seen in beetle elytron, [31] spider web, [32] bone, [33] tendon, [34] bamboo, [35] pomelo peel, [36] and grass stem. [37] Excellent crashworthiness is attributed to the hierarchical strategy, which has inspired the design of several novel honeycomb structures possessing superior mechanical properties. [38,39] Hierarchical structures are cellular materials composed of secondary substructural components having a complete structure. [40] In a broad sense, structural hierarchy can be achieved in two primary forms. [20] They are the vertex-based hierarchy (which is developed by replacing the vertices of the parent structure with substructures) and the edgebased hierarchy