Assessment and Modeling of Particle Filtration during the Liquid Composite Molding Process

Abstract

Numerous filler particles are being developed and applied to improve the properties of conventional composite materials or to develop composite materials with additional functionalities. When filler particles are added to the polymer matrix of a fiber-reinforced composite material, the particles dispersed in the polymer resin can be filtered between fiber strands during the manufacturing process, which leads to a nonuniform particle distribution and material defects. Therefore, understanding and controlling such filtration phenomena has become a critical issue. In the present study, a new microscopic methodology for measuring the distribution of filler particles in fully cured composite parts using an electron probe microanalyzer (EPMA) is proposed. The distributions of spherical titanium dioxide particles and carbon nanotubes conjugated with silver nanoparticles as tracers were visualized by elemental mapping analysis. Furthermore, the concentrations were separately measured in the intratow and intertow regions by quantitative analysis. Effects of the critical parameters of the manufacturing process on filtration were investigated. Numerical analysis was also performed to observe the spatial distribution of the filler particles and effects of process parameters over larger range which experimental analysis could not cover. A model for filtration rate was suggested in the form of the function of crucial variables such as permeability of porous media, resin viscosity, pressure gradient and concentration of particles according to the results of the analysis.