A model for the impregnation of resin into a unidirectional packed fiber mats by the dynamics of capillary penetration is developed at a low flow rate where resin flow is parallel to fiber axis. The model takes into account two types of flow, the macroflow around the fiber bundles and the microflow around the fibers in the bundles, occurring simultaneously. Both follows are described by Darcy's law. The large difference in the position of flow front between these two types of flow leads to the potential of void formation in resin transfer molding. The capillary force is considered along the flow front. It can be evaluated as a function of liquid contact angle, interfacial tension, the porosity, and the velocity of flow front. The simulation is based on the body-fitted finite element method. Result shows that the void formation is affected not only by the properties of fiber mars, but also by the injection condition. And the capillary effect is limited as the capillary number is less than 0(10(-2)).
