POISSONS RATIO OF FIBER-REINFORCED COMPOSITES

Poisson's ratio flow diagrams, that is, the Poisson's ratio versus the fiber fraction, are obtained numerically for hexagonal arrays of elas tic circular fibers in an elastic matrix. High numerical accuracy is a chieved through the use of an interface integral equation method. Ques tions concerning fixed point theorems and the validity of existing asy mptotic relations are investigated and partially resolved. Our finding s for the transverse effective Poisson's ratio, together with earlier results for random systems by other authors, make it possible to formu late a general statement for Poisson's ratio flow diagrams: For compos ites with circular fibers and where the phase Poisson's ratios are equ al to 1/3, the system with the lowest stiffness ratio has the highest Poisson's ratio. For other choices of the elastic moduli for the phase s, no simple statement can be made. (C) 1996 American Institute of Phy sics.