18. Sign-Switching of Poisson’s Ratio with Temperature Change Reversals

This chapter considers two examples of Poisson’s ratio sign-switching upon temperature change reversal using bimaterial strips with alternating orientation. In the first example, alternating signs of temperature change switches the microstructure between hexagonal-like cells and re-entrant-like cells. The former and latter are known for exhibiting positive and negative Poisson’s ratios, respectively. In addition to the CTE analysis, Poisson’s ratio analysis is included. In the second example, the cell walls are also made from alternating bimaterial strips, and are arranged in rectangular array with interconnecting rigid rods that are joined at the centers of the bimaterial strips. Fluctuating temperature flips the microstructure shape between octagon-like and star-like cells. Although only the CTE analysis is furnished for the second example, it is known that the interconnected star array manifests auxetic property. In spite of only thermal analysis, the effective CTE models developed can be converted to effective compressibility and effective CME models.