Modeling unsaturated flow in dual-scale porous media

Resin Transfer Molding (RTM) is widely used in the composites industry for producing Polymer Matrix Composite. In any typical RTM process during mold filling, a thermoset resin is injected/sucked into a mold cavity packed with a pre-placed preform of fiber mats. The purpose of this research is to study the unsaturated flow in dual-scale porous media created by the packed woven or stitched fiber mats in the RTM mold during the mold-filling process. The dual-scale porous media, which is characterized by the presence of large length-scale gaps between fiber tows with small-length scale pores, often results in rapid movement of resin in the gaps before the full impregnation of the surrounding tows, thereby leading to unsaturated flow with partial saturation of fiber mats near the resin front.;In the second chapter, a correlation between the previously proposed dimensionless numbers pore volume ratio (gamma) and sink effect index (psi), and the unsaturated flow through the resultant droop in the inlet-pressure history is sought. By studying the micrographs of composite samples, gamma and psi are measured for the biaxial and triaxial stitched mats at various states of compression.;In the third chapter, the effects of inlet-pipe expansion, bubble compression, and mold bulging on the inlet-pressure history in case of the radial flow is studied analytically. The formulated equations are solved numerically using Maple and the results show that the three considered parameters have a significant effect on not only the inlet-pressure history but on the front progress as well.;In the fourth chapter, the effect of change in flow direction on the unsaturated flow in two anisotropic dual-scale fiber mats is investigated. In the unidirectional woven mat, the maximum sink effect due to the unsaturated flow (correlated to the 'droop' in the inlet pressure history) is observed to be along the fiber tow direction and it decreases monotonically as the flow becomes perpendicular to the tows.;In the fifth chapter, the 1-D flow experiment as well as the transient and the steady-state radial flow experiments are used to estimate the permeability of a triaxial stitched (dual-scale) mat. Significant differences in the measured permeability values are observed from the three methods.;In the sixth, a new experimental procedure for calibrating the permeability measuring 1-D flow set-up is discussed. A reference porous media, consisting of a bank of parallel cylindrical holes is created whose theoretical permeability is computed using the Hagen-Poiseuille flow equation and whose numerical permeability is estimated using FLUENT. (Abstract shortened by UMI.).