Negative Compressibility in the Monoclinic Octahedron Model Constructed by Hinging Wine‐Rack Mechanism

Abstract

Enlightened by the concept of crystal system, many of the 3D models with negative compressibility that have been proposed so far are cellular models with periodic arrays, which can be called as orthogonal models or tetragonal models. Therefore, a more effective method to design 3D models with negative compressibility by changing the system type of the existing models can be developed. Herein, a monoclinic octahedron model based on the tetragonal octahedron model studied previously is proposed and its compressibility property is analyzed in detail through theoretical modeling. The specific conditions for the model to obtain negative compressibility are given in the discussion of on‐axis mechanical properties. The study about off‐axis compressibility shows that in addition to the geometric features, the measuring direction of compressibility and the arrangement of framework may also have a great influence on negative compressibility effect of the model.

Negative Compressibility in Hexagonal and Trigonal Models Constructed by Hinging Wine‐Rack Mechanism

“…Then, we quantitatively discuss the unity of the three models for the negative compressibility property. According to the previous work, [53,56] the expressions of the linear compressibility for the tetragonal octahedron model can be expressed as…”

“…However, the stretching and bending deformations of the rods cannot be avoided in practice. Therefore, the joints between the rods in the model are connected by flexible hinges as set in our previous work, [53,56] which can enhance the hinging deformation of the model as much as possible and weaken the stretching and bending deformations. The details of the flexible hinges at the vertex are shown in Figure 1d,f.…”

“…However, so far, there have been relatively few studies that extend negative compressibility to 3D space, and few methods have been proposed to build 3D models with negative compressibility. [53] Continuing our previous research [56] by changing the model system to design new models with negative compressibility, we conducted an extensive study to propose a hexagonal model and a trigonal model constructed by the hinging wine-rack mechanism. In general, the symmetry degree of the hexagonal and trigonal systems is the same as that of the tetragonal system; therefore, it can be inferred that the three models will have strong similarity and unity in the negative compressibility property.…”

“…[21] Since Baughman et al [21] first proposed this property, it has gradually attracted widespread attention owing to its unconventional mechanical properties. Thus far, a large number of micromaterials [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and macrostructures [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] have been proved to exhibit negative compressibility. As for micromaterials, negative compressibility has been found to occur in a much greater variety of materials, ranging from molecular, [22,23] metal-organic frameworks (MOFs), [24,25] and polymers.…”

“…Dudek et al [55] analyzed a 3D mechanical metamaterial composed of arrowhead-like structural units, which showed that the model exhibited auxetic behavior and manifested NLC. Recently, Ma et al [56] proposed a monoclinic octahedron model constructed by the hinging winerack mechanism based on the concept of the crystal system, which indicated that the new models with negative compressibility can be designed by changing the system of the models.…”