# Study of In-Plane Mechanical Properties of Novel Ellipse-Based Chiral Honeycomb Structure
## 1 Introduction
[34] conducted a theoretical derivations of [PERSON]'s modulus for several chiral honeycomb structures and polygonal lattice sandwich honeycomb structures based on the energy method and verified the correctness of the theoretical derivations by combining FEM simulations; [PERSON] et al. [35] and [PERSON] et al. [36] studied the elastic buckling of hex using theoretical derivations and FEM simulations, on the basis of which [PERSON] et al. [37] proposed a complete hysteretic elastic buckling model and mechanical characteristics of hex. In addition to the studies on the regular two-dimensional chiral honeycomb structures, many scholars have also conducted in-depth studies on the special two-dimensional chiral honeycomb structures [38; 39] and three-dimensional chiral honeycomb structures [40; 41; 42; 43; 44; 45]. NPR honeycomb structures have been widely used in various fields due to their performance advantages [46; 47; 48; 49], but the disadvantages of weak load-bearing capacity [50] of two-dimensional NPR honeycomb structures limit the relevant engineering applications. Some scholars have already made corresponding improvements based on the disadvantages of the low Young's modulus of the NPR honeycomb [51; 52; 53]. Recently, [PERSON] et al. [54] developed microstructures that can exhibit multidirectional auxeticity covering the in-plane and out-of-plane directions including mixed-mode modulation. The proposed 3D microstructure could be extended to different other beam profiles with spatially varying geometrical and material parameters, making it an ideal candidate for the creation of innovative programmable structural systems. To the best of our knowledge, no  
Figure 1: Circular node ring chiral structures: (**a**) tri; (**b**) antitri; (**c**) tet; (**d**) antitet; (**e**) hex. study has been conducted in the open literature to improve the central node to enhance the in-plane Young's modulus of chiral honeycomb structures, so it is necessary to study new chiral honeycomb structure. However, this area of research is still far from enough due to the large porosity of NPR structures. In addition, conventional NPR materials are often designed as isotropic structures, which limits the adjustment range of negative Poisson's ratio to some extent. In this paper, we design an elliptical anti-tetrachiral honeycombs structure (E-antitet) with orthogonal anisotropic elastic constants, which can improve its material strength in at least one direction and has a wide range of Poisson's ratio adjustment. This gives our proposed E-antitet a more flexible means of regulation. The paper is organized as follows: Section 1 introduces the research advances, specific applications and current disadvantages of NPR honeycomb structures, especially chiral honeycomb structures; Section 2 shows the theoretical derivations, FEM simulations and experimental validation of the in-plane mechanical properties of E-antitet; Section 3 analyzes the effects of parameters on the in-plane mechanical properties of E-antitet; Section 4 summarizes the full work. Theoretical Derivations, FEM Simulations and Experimental Verification of In-Plane Mechanical Properties of E-Antitet