Modeling and computer simulation of the compressional behavior of fiber assemblies - I: Comparison to van Wyk's theory

A model is presented that allows prediction of the properties of a fiber assembly under compression from the physical properties of its component fibers, taking into account both static and kinetic friction. Unlike previous models, this model is not based on the assumed behavior of idealized bending elements. Computer simulations are run for four cases with two different friction conditions in order to compare predictions of this model with experimental results and with van Wyk's theory of the uniaxial compression of an initially random fiber assembly. These simulations are the first to show a reasonable ability to predict the undetermined constant K in van Wyk's equation. They also show a significantly greater number of fiber-fiber contacts being formed than theories based only on the diameter and arrangement of fibers have predicted. The predicted contacts have a wide range of contact forces, while only a small percentage of them do not slip. Further improvements to the predictive abilities of this model may be obtained by running larger simulations, modifying the boundary conditions, and incorporating a more realistic friction model.