Modeling of fiber–polymer coupling for suspensions of mono‐modal fibers

Abstract The rheology of suspensions of fibers in polymer solutions is strongly dependent on fiber–fiber and fiber–polymer interactions. To model these interactions and their dependence on the flow and suspension properties, the steady shear viscosity of glass fibers in a polyethylene oxide polymer solution are measured for different fiber volume fractions and aspect‐ratios. The measurements are conducted for well characterized fiber samples that have a uniform and well defined aspect‐ratio and for moderate volume fractions. The results of the experimental study are used to correlate the polymer–fiber coupling factor and the fiber–fiber interaction coefficient using a mathematical model based on a modified FENE‐P (finitely extensible nonlinear elastic) constitutive equation. It was found that both parameters are strongly dependent on the characteristics of the suspension, but also depend on the flow shear rate that determines the degree of fiber orientation. In general, fiber–fiber and polymer–fiber interactions increase with both the aspect‐ratio and the volume fraction and are more important when the fibers are not fully oriented. POLYM. COMPOS., 27:82–91, 2006. © 2005 Society of Plastics Engineers