Normal stress differences in suspensions of rigid fibers*

Numerical and experimental studies of normal stress differences in suspensions of rigid, non-Brownian fibers were carried out for length (L) to diameter (d) ratios of 11 to 30 at concentrations nL$^{\mathrm{2}}$d$=$1.5 to 3, where n is the number density of fibers. The numerical results are in quantitative agreement with the experimental results and allow calculation of the hydrodynamic and contact contributions to the stress in the suspension. The simulations show that the contact contribution to the rheology is dominant in determining the normal stress differences, where the first normal stress difference is positive and approximately twice the magnitude of the second normal stress difference, which is negative.