3. Flows of Simple Fluids in Complex Microstructures: Composite Processing of Structural Polymer Composites

Continuous fiber reinforced polymer (CFRP) always involves a fluid flow through the fibrous medium, whether to create a semi-product like a prepreg that will be further processed to make the final part or to directly manufacture a part from dry fiber reinforcement. This chapter discusses the physics and modeling of flow of simple fluids within complex microstructure. Microstructure refers here to features of internal structure of engineered fibrous materials used to reinforce polymer composites. As already mentioned earlier in this book, the flow is greatly influenced by the type of fibers being used and is viewed as key for ensuring successful fabrication. This chapter has a complementary focus as compared to Chap. 2. Here only media made of continuous fibers are considered. An important characteristic of continuous fibers is that they cannot flow with the polymer, even if the viscosity of the polymer is low. This chapter reviews the modeling of viscous resin into a porous network of stationary fibers, at a variety of length scales. As far engineered fibrous materials are concerned, the appropriate length scales are those that reveal the partition of the fibrous media into regions of nearly continuous phase such as continuous fibers and cluster of fibers called fiber bundles.