Filtration of Particles through a Single Layer of Dual Scale Fibrous Porous Media

Abstract

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 a resin infusion process. In this process, preforms of glass, aramid or carbon fabric are stacked in a closed mold and resin with suspended micron-sized particles is injected into the mold. The preforms are usually fabrics with yarns or bundles of thousand or more micron-sized fibres 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 dual-scale nature of the fabric creates a network of pore sizes through which the resin will flow to cover the fibres, but the infiltration and the final concentration distribution of the particles will establish the gradient of the properties in the composite. In this paper, we present a model to predict the concentration distribution of particles within this dual-scale fibrous porous media infused under a constant pressure drop. The approach uses Darcy's law and accounts for lowering in the permeability value due to the particle entrapment in the available pores. Experiments are conducted and the concentration of the particles in the fabric is measured. The results compare well with the predictions despite many assumptions made in the model. A non-dimensional analysis is conducted and a parametric study explores the influence of critical non-dimensional parameters on the filtration efficiency.