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.