A novel mechanism for auxetic behavior in entangled materials with a spiral wire structure

Abstract

New kinds of entangled materials with an auxetic effect were investigated in terms of fabrication, structural characterization, the measurement of their negative Poisson’s ratio and the auxetic mechanism. The maximum negative Poisson’s ratio of −1.5 was obtained at about 5% of the engineering strain for the entangled materials with 45% porosity. The auxetic behavior originated from the rotation of the ‘slanted coil-springs’ structure. A model to formulate the negative Poisson’s ratio was proposed based on the slanted coil-spring structure. The initial slanted angle affected the auxetic behavior significantly. As the slanted angle decreased, the negative Poisson’s ratio increased. Entangled materials with such an auxetic effect have potential for engineering applications.