Negative homogenized characteristics of laminated composites

Recently, the 40th anniversary of materials exhibiting negative characteristics was celebrated. The pioneering work began in 1984 when Herakovich [1] designed a layered composite with a negative Poisson’s ratio across the layers, followed in 1985 by inverse honeycomb designs [2, 3]. In 1986, Kolpakov and Rakin [4] introduced a layered composite with a negative coefficient of thermal expansion across the layers. Given two major periods of interest in composites with negative properties, one during the 1990s and 2000s, and another ongoing today, we revisit these pioneering layered composite models from a contemporary perspective. This paper demonstrates that although negative coefficients (Poisson’s ratio and thermal expansion coefficient) are rare in natural materials, they can be achieved in layered composites constructed from homogeneous material layers, the simplest composite structure designs. Using illustrative metamaterial models, we provide visual explanations of the micromechanical mechanisms underlying these negative-coefficient phenomena.