Making and Characterizing Negative Poisson's Ratio Materials

We present an introduction to the use of negative Poisson's ratio materials to illustrate various aspects of mechanics of materials. Poisson's ratio is defined as minus the ratio of transverse strain to longitudinal strain in simple tension. For most materials, Poisson's ratio is close to 1/3. Negative Poisson's ratios are counter-intuitive but permissible according to the theory of elasticity. Such materials can be prepared for classroom demonstrations, or made by students.