PERMEABILITY CHARACTERISTICS OF MULTILAYER FIBER REINFORCEMENTS .2. THEORETICAL-MODEL

The permeability characteristics of multilayer fiber networks generally differ from those of the constituent layers. In heterogeneous assemblies, the effective in-plane permeabilities and flow anisotropies are governed by the high permeability layers or directions. Based on the observation that a transverse flow mechanism contributes to filling the low permeability layers, a semipermeable wall model has been constructed to analyze encroaching flows into multilayer systems. The model identifies three flow regimes: a region in which the layers act independently and are governed by single layer solutions, a region in which the layers act as a unified homogeneous system governed by the single layer solution with weighted average properties, and a region intermediate to these extremes. A comparison of model simulations and experimental data demonstrates that the model has good predictive capabilities.