Fiber-fiber interaction in concentrated suspensions: Disperse fibers

A hypothesis for fiber-fiber interaction in planar randomly oriented concen trated fiber suspensions is proposed and tested. The idea is that at suffic iently high fiber concentrations, friction and lubrication at fiber-fiber c ontact points are the dominant interaction mechanisms. A fiber pull-out tec hnique is introduced to measure the force per unit fiber length on a single longitudinally moving fiber embedded in a volume of bulk suspension. By va rying both the fiber velocity and the fiber volume fraction, the lubricatio n and frictional components of the force are identified. Furthermore, the c orresponding bulk shear viscosity resulting from the same mechanisms is der ived and compared with experimental data. The results support the hypothesi s. (C) 1999 The Society of Rheology. [S0148-6055(99)00204-7].