Visualization and quantification of forced in-plane flow through deformed porous media

Fluid flow in liquid molding processes and in other applications involving porous media is often characterized with a permeability tensor and modeled by d'Arcy's law. The permeability is a sensitive function of pore structure , which, in deformable materials, is influenced by compression and extensio n. The majority of previous permeability measurements on composite reinforc ement fabrics did not account for deformations imposed on them by corners a nd curves in the mold. In the present study, transparent molds were designe d with a single 90 degrees bend in which the gap between plates was held co nstant throughout the flow path. Thus, the effects of fabric curvature on p ermeability were investigated independently of the effects of fabric compre ssion in the thickness direction, A new experimental system was developed t o visualize and quantify fluid flow in fabrics mounted in transparent molds . The reported measurements were conducted with fluid flowing through a (ve rtical) flat region of fabric, around the 90 degrees curve, and then along a second (horizontal) flat region. Permeability was found to be reduced by the imposed curvature for a nonwoven polyester and three-dimensional woven glass fabric. We were able to quantify the effect of curvature on permeabil ity for the former, but not for the latter because of an enduring, dominant nonlinear entrance resistance. For the glass, comparison of two now rates indicates that the faster flow is characterized by a two stage filling proc ess, whereas, at the slower rate, the liquid front fills all pores at the s ame time.