Longitudinal and transverse flows in fiber tows: Evaluation of theoretical permeability models through numerical predictions and experimental measurements

Tow permeability is a very important input in the dual-scale flow and void formation studies in Liquid Composite Molding processes for manufacturing polymer composites. In this comparative study aimed at checking the accuracy of various theoretical models for permeability, we evaluated the permeability of unidirectional fibrous media at tow scale for flow transverse and parallel to the fiber directions. The falling-head parameter was adapted to measure the permeability along and across the fibers within tows for three different cases of fiber volume fractions (fvf). Unit cells corresponding to the measured fvf and fiber diameters were generated using GeoDict. Two separate simulations, one using GeoDict to solve Stokes flow and the other using COMSOL to solve Whitaker's closure-formulation, were done. Eighteen different analytical models were evaluated.