An investigation into the hydraulic properties of needle-punched nonwovens for application in wet-press concrete casting Part II: Predictive models for the water permeability of needle-punched nonwoven fabrics

A review of various models for predicting the water permeability of fibrous structures is reported. Using the Hagen-Poiseuille formula, a modified form of the Kozeny-Carman equation was derived. An apparatus was constructed that enabled cross-plane and in-plane water permeabilities of various needle-punched nonwoven fabrics to be measured under a range of compressive loads applied to the fabrics. Fabrics were made from 3, 6, 10, and 17 denier polypropylene fibres and the measured permeability values were compared with predicted values obtained from the various models. Three of the models gave reasonable agreement with the experimental data for cross-plane water permeability. However, a suitable model has yet to be developed which gives adequate predictions of the in-plane water permeability of needle-punched nonwoven structures.