Study on void formation in resin transfer molding

A 2-D model has been developed for the transverse impregnation of a resin into a unidirectional packed fiber mat. The model takes into account two types of flow, macro-flaw around the fiber bundles and micro-now around the fibers in the bundles, which occur simultaneously. Both flows are described by Darcy's law. Results show that if the ratio of permeability of the macro-now to the micro-flow is more than 20, an elliptic type void is formed within the fiber bundle, and the void will shrink and disappear if vacuum assistance is applied in the mold. The capillary effect was also investigated by use of a numerical simulation based on a body-fitted finite element method and by experiment. A correlation between the capillary force and other parameters is proposed for the XT-D/O unidirectional fiber mat. The quasi-equilibrium capillary effect is limited to when the modified capillary number is about O(10(-4)).