  A flexible fiber model based on the discrete element method (DEM) is
presented and validated for the simulation of uniaxial compression of flexible
fibers in a cylindrical container. It is found that the contact force models in
the DEM simulations have a significant impact on compressive forces exerted on
the fiber bed. Only when the geometry-dependent normal contact force model and
the static friction model are employed, the simulation results are in good
agreement with experimental results. Systematic simulation studies show that
the compressive force initially increases and eventually saturates with an
increase in the fiber-fiber friction coefficient, and the fiber-fiber contact
forces follow a similar trend. The compressive force and lateral
shear-to-normal stress ratio increase linearly with increasing fiber-wall
friction coefficient. In uniaxial compression of frictional fibers, more static
friction contacts occur than dynamic friction contacts with static friction
becoming more predominant as the fiber-fiber friction coefficient increases.
