Negative Environmental Expansion for Interconnected Array of Rings and Sliding Rods

Abstract

Materials and structures are exposed to simultaneous fluctuations in temperature, pressure, and moisture in the environment, which result in additional stresses and strains in addition to mechanical loadings. This paper develops the effective coefficient of thermal expansion (CTE), coefficient of moisture expansion (CME), and compressibility for the interconnected array of ring and sliding rod structures made from conventional materials, wherein conditions that lead to negative thermal expansion (NTE), negative moisture expansion (NME) and negative compressibility (NC)and hence the negative environmental expansion (NEE)are established. The above-mentioned coefficients shift toward negative values as the ratio of ring-to-rod expansivity increases. The established effective CTE, CME, and compressibility not only permit the requirements for NTE, NME, and NC to be ascertained, but also allow the less restrictive condition of zero environmental expansion to be implemented in the design of materials and structures, without requiring zero CTE, CME, and compressibility.

Composite metamaterial square grids with sign-flipping expansion coefficients leading to a type of Islamic design

“…concentration in materials 1 and 2 (dC 1 , dC 2 ) in a twophase composite wherein dC ≠ dC 1 ≠ dC 2 at moisture transfer equilibrium. This is unlike temperature change where dT = dT 1 = dT 2 is attained at thermal equilibrium [40]. Analogies can be formed with the various coefficients of expansion and their corresponding strains and environmental changes, as listed in Table 1.…”

“…Their investigation provides distinctive sensing results and therefore avails a novel method to the microfluidic sensor applications by using the sample holder. Although negative material properties-such as negative Poisson's ratio [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], negative thermal expansion [23][24][25][26][27][28][29][30][31], negative compressibility [32][33][34][35][36][37] and negative moisture expansion [38][39][40]-have been investigated for a few decades due to their capability of behaving in ways that are not achievable by conventional materials, it remains that some applications may require both positive and negative properties depending on the circumstances. For this reason, a series of metamaterials in which their effective material properties can switch between positive and negative signs have been introduced.…”

Negative Hygrothermal Expansion of Reinforced Double Arrowhead Microstructure

“…These “mechanical negative materials” comprise negative Poisson's ratio (NPR) or auxetic materials, “negative thermal expansion” (NTE) materials, “negative compressibility” (NC) materials, and “negative stiffness” phases . Adding to these, the possibility of “negative hygroscopic expansion” (NHE) or “negative moisture expansion” (NME) materials was recently discussed; an NHE material is one that contracts upon absorption of moisture. Although investigations into moisture expansion are less than that for temperature expansion, the former is nevertheless important when dealing with structures made from materials that can absorb and dissipate moisture (e.g., refs …”

Maximum Stresses in Rectangular Auxetic Membranes

“…Since its rediscovery in the late 1980s, [9][10][11][12][13] auxetic materials have been investigated for applications as cushions, [14,15] footwear, [16,17] aircraft structures, [18,19] shock and vibration control, [20][21][22][23][24][25] technical textiles, [26,27] chemical filters, [28][29][30][31] implants, [32][33][34][35][36][37] safety devices, [38] composite structures, [39,40] and even sport safety gear. [41,42] Further details of auxetic materials can be found in recent reviews by Saxena et al, [43] Lim, [44] Lakes, [45] and Ren et al [46] as well as recent special issues on auxetics in Physica Status Solidi B (e.g., previous studies [47][48][49] ), Materials (e.g., previous studies [50][51][52] ), and two monographs. [53,54] While auxeticity has often...…”