Natural bee honeycomb-inspired RH-FP: (a) conventional manmade honeycomb; (b) natural bee honeycomb with folding partition; (c) unit cell of the (ⅰ) main reentrant honeycomb, (ⅱ) folding partition, (ⅲ) RH-FP, and its (ⅳ) NPR behavior under compression in y direction; (d) top view; (e) side view; and (f) specific details of 3D printed RH-FP with = 20.8 deg, = 32.2 deg, and = 0.05. Points A, B, C, and D were used to calculate Poisson's ratio in the digital image correlation method. Scale bars of (d) and (e) are 3 mm and for (f) is 100 μm.
Natural bee honeycomb-inspired RH-FP: (a) conventional manmade honeycomb; (b) natural bee honeycomb with folding partition; (c) unit cell of the (ⅰ) main reentrant honeycomb, (ⅱ) folding partition, (ⅲ) RH-FP, and its (ⅳ) NPR behavior under compression in y direction; (d) top view; (e) side view; and (f) specific details of 3D printed RH-FP with = 20.8 deg, = 32.2 deg, and = 0.05. Points A, B, C, and D were used to calculate Poisson's ratio in the digital image correlation method. Scale bars of (d) and (e) are 3 mm and for (f) is 100 μm.
Abstract
Honeycomb structures, inspired by bee honeycomb, are one of the most efficient engineering materials. They were usually used as 2D honeycomb cores and honeycomb sandwich panels. However, a natural bee honeycomb is a 3D cellular material with a folding partition. Herein, by introducing a folding partition in a reentrant honeycomb, we proposed a class of 3D closed-cell plate-based mechanical metamaterials with negative Poisson's ratio (NPR). Ultrahigh stiffness, 36% greater than the Hashin–Shtrikman upper bound, and excellent load-bearing capability, 2 × 105 times its own weight, has been observed in the compression of these 3D plate-based NPR metamaterials. The NPR behavior of these materials is found to be essentially governed by the NPR mechanism of the reentrant structure. The excellent stiffness and strength in turn drive from both the excellent load bearing of the augmented structure and the NPR behavior of the whole structure. Overall, the proposed strategy paves the way for designing 3D plate-based NPR metamaterials with superior mechanical properties and could be employed in civil engineering structures, cores of military armors, as well as functional sensing devices.
