AUXETICITY WINDOWS FOR COMPOSITES

Materials with negative Poisson ratios are known to have high shear ri gidities - a useful property for many types of structural and function al materials. To improve upon relatively low Young's modulus of existi ng auxetics, one may consider embedding such components in an elastic material with sufficiently high modulus. We show theoretically that su ch composite materials do exhibit auxeticity when the inclusion volume fraction exceeds a critical value and the ratio of Young's modulus of inclusion to that of a matrix falls within a definite interval. The e xistence of these auxeticity windows, once verified experimentally, op ens up a new avenue of auxetics research. (C) 1998 Elsevier Science B. V. All rights reserved.