In-Plane Permeability of Stitched MMWK Laminates in Resin Transfer Molding

Resin Transfer Molding (RTM) involves the injection of liquid resin into a closed mold preloaded with dry preforms. For planar composite structures, the in-plane permeability should be determined prior to the injection process in order to predict the fluid flow and fill time progress. In this work, the in-plane permeability of multi-layer multi-directional warp knit (MMWK) laminates stitched using Kevlar fiber were measured using radial flow visualization experiments. The visualization demonstrated that the in-plane permeability of MMWK laminates is highly anisotropic and significantly influenced by the Kevlar stitches. Results showed that the major principal permeability, k _x , decreased with an increase in stitch density. Although the stitches resulted in an increase in minor principal permeability, k _y , it seems that the increase in stitch density did not result in an obvious change in k _y .