Tow impregnation of unidirectional fibrous preform during resin transfer molding

The flow pattern determines the formation and distribution of the voids. and subsequently the quality of the products during the mold filling of RTM. A model is developed to simulate the interaction between the flow in the gaps around the fiber bundles and the flow inside the fiber bundles. Brinkman's equation is used to calculate the flow fields inside the fiber bundles, while the Stokes approximation is used to simplify the resin flow equation in the gaps. Results show that the mechanism of air entrapment is formed inside the fiber bundles. A boundary layer occurs along the permeable interface of the fiber bundles. The thickness of the boundary layer increases with large permeability and larger gap size. The thickness of the boundary layer is about O(K-1/2). For flow outside of boundary layer regions the Brinkman's equation can reduce to the Darcy's law.