The interactions between flows occurring inside and outside fabric tows during RTM

Resin-transfer molding is finding use in structural and complex-shaped polymer composites. Simultaneously, preform technology improvement leads to the design of more intricate and heterogeneous fibrous reinforcements. This architectural design favors the increase of flow scales in the fibrous materials, making impregnation modeling more difficult. Hence, the micro-flows are often neglected in current fluid-flow models without real scientific justification. The interactions between microscopic and macroscopic flow in woven fabrics have been theoretically and experimentally investigated This work indicates that, in the region close to the flow front, tow impregnation leads to a lag in the fluid motion in the more open regions bounding these fiber bundles. A model to predict this velocity drop is proposed. This effect is found to be significant, and should be taken in account in developing more accurate models, especially for high fiber-content preforms. (C) 1997 Elsevier Science Limited.