Three-dimensional auxetic materials with controllable thermal expansion

Abstract

Thermal expansion and stress of solid materials can significantly affect structural safety and instrument accuracy in many engineering fields. An alternative way to overcome these drawbacks is to use materials with controllable coefficients of thermal expansion (CTEs). This work presents a new three-dimensional (3D) material with controllable CTEs that is composed of chiral honeycomb layers connected by a set of inclined struts. Although each single chiral layer has positive CTEs, by carefully designing geometric parameters and material constituents, the negative thermal expansion (NTE) can be established. Analytical solutions of the equivalent CTEs are proposed using the classical beam theory, which were verified by finite element simulations. The results show that the proposed material can achieve a large range of CTEs (from positive to negative), and has negative Poisson's ratios in the chiral honeycomb planes. In addition, isotropic negative and zero thermal expansion can be obtained with appropriate design parameters.

Auxetic mechanical metamaterials: from soft to stiff

“…Two-dimensional (2D) and three-dimensional (3D) auxetic cellular materials with regular porous structures are an important part of auxetic materials [31][32][33][34][35]. Their mechanical properties can be designed according to demand [36], such as auxetic cellular structures with negative thermal expansion coefficient [37,38], negative linear compressibility [39], negative stiffness [40], negative wet properties [41], extraordinary bending Poisson's effect [42], and strain ratedependent Poisson's ratio [43]. In this paper, auxetic materials with regular structure are termed as auxetic structures.…”

Thermal Expansion of Hybrid Chiral Mechanical Metamaterial with Patterned Bi‐Strips

“…For mechanical metamaterials, desired CTE can be achieved through mechanical or structural interactions between architected components with different thermal responses. [4,[18][19][20][21] Usually, such interactions induce localized bending or rotation of certain structural components in the internal free space, allowing for tunable overall thermal expansion or contraction.…”

“…Mechanical metamaterials with various structural configurations have been studied systematically, including planar structures based on triangle lattices, [6,[22][23][24][25][26][27][28][29] chiral or antichiral lattices, [3,20,[30][31][32] and other geometries, [4,[33][34][35][36] and threedimension (3D) truss structures. [37][38][39][40][41][42] Also, mechanical metamaterials with both NTE and other unusual properties, such as negative Poisson's ratio, were designed.…”

Bifunctional Metamaterials Incorporating Unusual Geminations of Poisson’s Ratio and Coefficient of Thermal Expansion

“…In contrast, metamaterials consisting of the artificial “meta-atoms” could bring out various novel functionalities and, therefore, attract widespread attention. The study on designing such bifunctional metamaterials is scarce, of which the resultant designs can be largely traced to the common auxetic metamaterials, such as re-entrant ,− and chiral types. − To achieve the unusual behavior of thermal expansion, bimaterial layouts are successively developed to reconstruct the original architectures based on the experience or inspiration of researchers, including the bimaterial strip , and bimaterial triangle. − , …”

“…Therefore, the means to gain more novel and excellent architectures pose a challenge for the design of bifunctional metamaterials. Another limitation is that most of the reported bifunctional metamaterials just ended with the conceptual design and theoretical analysis without the practical manufacturing and experiments, ,,− ,− exposing the significant lack of effective prototyping and characterization.…”