The theological behavior of suspensions of short glass fibers in different
fluids has been studied. Transient tests on presheared samples of fiber sus
pensions in Boger fluids showed that orientation of fibers not only depends
on the strain, but also on the rate-of-strain. The experimental results sh
ow that upon increasing fiber concentration and/or fiber aspect ratio, the
steady shear material functions of fiber suspensions increase at low shear
rates, whereas at high shear rates, these material functions approach those
of the matrix and become almost independent of fiber characteristics. A th
eological model based on the modified Jeffery equation for the fiber motion
and a Hookean energy model, formulated within the GENERIC framework, for t
he matrix has been developed to quantitatively predict experimental data fo
r suspensions of fibers in different fluids. A quantitative comparison of e
xperimental data with model predictions shows the ability of the model to p
redict the theological behavior of fiber suspensions in viscoelastic media.
(C) 2001 The Society of Rheology.