Permeability and resin flow measurements and simulations in composite preforms

In the resin transfer molding process (RTM), where the resin is injected into a mold containing a reinforcement preform, resin flow through the reinforcement plays a crucial role. This flow can be described by Darcy's law and is a function of the permeability of the preform and viscosity of the resin. These properties of the preform and resin are used in flow analysis and modeling aimed at predicting the resin flow pattern within the mold. The permeability of three types of composite fiber preforms (loose plain weave, tight plain weave and unidirectional mat) was measured by the fluid injection method. Flow front measurements were made by using rectangular molds with transparent tops and injecting silicon fluid at the center with different degrees of preform compaction. The resin flow through the preform was also simulated with a control volume finite element method (CVFEM). The effects of injection pressure, type of reinforcement and mold geometry on flow in the mold were investigated. Flow modeling results were verified by conducting experiments with molds containing inserts and varying gate locations. Good agreement was obtained between model predictions and experimental results.