Modeling of filtration process during manufacturing of functionally graded composites with particulate suspensions

Functionally Graded Composites exhibit properties or functions within the material that vary gradually or in a stepwise manner without a recognizable boundary. One technique to manufacture Functionally Graded Polymer Composites is by Liquid Composite Molding process. Liquid molding process is amenable for manufacturing large-scale composite structures. In this process, fiber preforms of glass, Kevlar or carbon fabric are stacked in a closed mold and resin is injected into the mold. Particles may be added to the resin to tailor the properties of the final product. The preforms used are usually fabrics with yarns or bundles of thousand or more micron size fibers woven, stitched or knitted together. This architecture gives rise to a bimodal distribution of pore sizes; the larger pores in between the bundles and smaller ones within the bundles. The filtration process that takes place during infusion alters the flow resistance of the porous media as well and complicates the impregnation process. In this study, a Vacuum Assisted Resin Transfer Molding (VARTM) process based approach is presented that enables functional grading in composites to obtain a desired distribution in properties. (Abstract shortened by UMI.)...