Directional Permeability in Homogeneous Nonwoven Structures Part I: The Relationship between Directional Permeability and Fibre Orientation

A new general model of the directional permeability in homogeneous, anisotropic nonwoven structures is presented. It is based on drag-force theory and D'Arcy's Law. Structural parameters in the fabric are considered, including fibre diameter, porosity, and the fibre-orientation distribution. The governing equations of the local permeability in two- and three-dimensional structures are derived, which allow the permeability in any direction in the fabric to be calculated. It is demonstrated that fibre orientation is a major factor influencing the anisotropy of permeability.

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