In-plane crashworthiness of re-entrant hierarchical honeycombs with negative Poisson’s ratio

Abstract

Both auxetic structures and hierarchical honeycombs are marked with lightweight and excellent mechanical properties. Here, we combine the characteristics of auxetic structures and hierarchical honeycombs, and propose two re-entrant hierarchical honeycombs constructed by replacing the cell walls of re-entrant honeycombs with regular hexagon substructure (RHH) and equilateral triangle substructure (RHT). The honeycombs are subjected to in-plane impact in order to investigate the crashworthiness by using the commercial software LS-DYNA. The plateau stress of RHH and RHT in x and y directions are derived by a two-scale method. The results from numerical simulation indicate that the specific energy absorption of RHT and RHH is improved by up to 292% and 105%. RHT and RHH improve the mean crushing force value by 298%, 108% respectively compared with the classic re-entrant honeycomb (RH) under quasi-static loading at stress plateau region. The RHT and RHH still have the characteristic of negative Poisson's ratio. Additionally, the parametric studies are further carried out to investigate the effects of impact velocities and relative densities on crashworthiness. All the findings of this study indicate that the proposed two hierarchical honeycombs exhibit an improved crushing performance, and RHT provides the highest energy absorption capacity among all specimens.

Energy Absorption Enhancement by Unit Cell Angle Grading or Sandwich Panels with Auxetic Core

“…A lot of effort has been put to analyze the static and dynamic energy absorption capabilities of auxetic structures, through both experimental and numerical methods. For example, Tan et al [22] parametrically studied the deformation modes and energy absorption capabilities of re-entrant hierarchical hexagonal honeycombs and demonstrated that both their proposed solutions exhibit an improved crushing performance. To further improve the energy absorption performance in impact, Wang et al [23] designed and studied a novel auxetic structure named re-entrant star-shaped honeycomb (RSH) and showed, through both experimental and numerical simulation, that RSH shows excellent impact resistance, compared with the classical re-entrant honeycomb (RH) with same cell wall thickness.…”

Stacked-origami mechanical metamaterial with tailored multistage stiffness

“…Interestingly, Li and coworkers combined the stacked Miura origami and rhombic honeycomb structure to develop new mechanical metamaterials with a two-stage programmable compressive strength [50]. The concept of this combination of different configurations to gain incredible performances has received considerable attention in many fields [51]. Alternatively, introducing additional microstructures to the mechanical metamaterial is another promising way to significantly improve the performance [52,53].…”

A New Type of Hierarchical Honeycomb in-Plane Impact Study

“…Additional studies on hierarchical honeycombs have added substructures such as squares, hexagons, and kagomes [ 23 , 24 , 25 , 26 , 27 , 28 ]. H. L. Tan et al added triangular subunits into concave hexagons and obtained excellent mechanical properties [ 29 , 30 ].…”

“…Additional studies on hierarchical honeycombs have added substructures such as squares, hexagons, and kagomes [24][25][26][27][28][29]. H. L. Tan et al added triangular subunits into concave hexagons and obtained excellent mechanical properties [30,31]. However, when these honeycomb structures [23][24][25][26][27][28][29] are subjected to quasi-static impact, the strain corresponding to the linear elastic zone is relatively large and cannot reach the platform zone quickly, therefore, the energy absorption effect is poor in the early stage.…”