A DUAL-PERMEABILITY NETWORK MODEL FOR MULTILAYER WOVEN FABRICS

Abstract

An analytical permeability model is formulated for multilayer plain woven fabrics based on a network treatment. Both meso-scale flow between fibre tows and micro-scale flow within tows are taken into account, addressing the effects of meso-/micro-structures of fabrics. For a single layer fabric, open channels between adjacent fibre tows and between fibre tows and surface boundaries have a significant effect on in-plane permeability, while out-of-plane permeability is sensitive to open gaps between tows. It is shown that the permeability of multilayer woven fabrics may differ significantly from that of a single layer, depending on the meso-/micro-structures of multilayer fabrics. Two major mechanisms are found to affect the in-plane permeability of multilayer fabrics in opposite ways. As the number of layers increases, the large inter-layer open channels created after laying-up result in an increase in in-plane permeability; on the other hand, reduction of inter-layer open channels due to nesting during a compaction process leads to a decrease in in-plane permeability. In addition, reduction of trans-layer open channels due to inter-layer blocking associated with shifting also greatly reduces the out-of-plane permeability of multilayer fabrics. Predictions from the permeability model offer satisfactory agreement with the experimental data and the predictions based on finite element analysis.