THE INTERACTION BETWEEN MICROSCOPIC AND MACROSCOPIC FLOW IN RTM PREFORMS

Both experimental and modeling results are presented to convey the wid e span of length scales over which flow in porous media can occur in a single material. Flow in such heterogeneous porous media are shown to be important in composites processing because the structure of fibrou s reinforcements contains multiple length scales. Flow phenomena that arise due to material heterogeneity have been shown to include void fo rmation and to explain the differences observed between measurements o f the 'wet' permeability and the 'dry' permeability. The work presente d indicates that the heterogeneous reinforcement structure may also co ntribute to the differences observed in permeability measurements carr ied out by the radial flow and the one-dimensional flow methods. The c oncept of heterogeneous porous media is also extended to the molecular level by considering the flow problem in a reinforcement sized with g rafted macromolecules.