Effect of dual scale porosity on the overall permeability of fibrous structures

The porous homogenised tow model is then used to study the effect of inter-tow and intra-tow porosity on the overall permeability. It is shown that the effect of intra-tow porosity on the overall permeability is insignificant, while the inter-tow porosity on the other hand has a very strong influence on the overall permeability. Good correlation is also shown with results from previous experimental and numerical studies. For relatively low tow to filament radius ratios (Rt/Rf) there can be some influence from the intra-tow porosity on the overall permeability. However, it is negligible for higher ratios (Rt/Rf>102), i.e. in the regime where most fibre reinforcements for composite materials are found.