Effective scale of microstructure of fibrous permeable materials

Microstructure properties of fibrous permeable materials, such as effective porosity, pore size and tortuosity, and related transport phenomena, is of great importance to many practical and industrial application, as well as in several manufacturing process-es. Several resistance models, based on Darcy’s law and Forchheimer’s equation, were derived through the last decades to predict the behavior of fluid flow and permeability in fibrous materials. In existing resistance models the effective scale of microstructure (also called specific surface area or pore size), is assumed as the hydraulic diameter of the capillary in Hagen-Poiseuille law, from Carman geometrical model. Nevertheless, the disordered nature of fibre arrangement suggests the existence of different relation-ships, linked to the transport phenomena within the fibre network. In this work a new approach is proposed in order to evaluate the effective scale of microstructure (in terms of pore size) of fibrous permeable materials.