A permeability prediction for non-crimp fabrics

A model is proposed to analyse the variation in the permeability of Non–Crimp Fabrics, originating from variations in the internal structure of the material. A geometrical description of the fabric based on the distortion induced by the stitch threads piercing through the fabric is employed. The distortions form channels which are mutually connected. It is assumed that these channels dominate the permeability of the fabric. A network of flow channels is subsequently defined, in which the variations, measured in the dimensions of the distortions, is explicitly accounted for. The variations in the internal structure of the fabric affect the averaged permeability significantly. Moreover, a network rather that a single unit cell is required to predict the averaged permeability and its variation properly. Finally, the spatial distribution of the randomly generated channel dimensions affects the permeability significantly