Dr. Thanasis D. Papathanasiou, Professor and Head，Department of Chemical and Materials Engineering, Nazarbayev University,Republic of Kazakstan

Title: STRUCTURE-ORIENTED MODELS FOR THE PERMEABILITY OF ACROSS RANDOM AND AGGREGATED FIBER ARRAYS

Abstract: We investigate computationally the effect of randomness as well as the effect of fiber aggregation on the hydraulic permeability (K eff ) of unidirectional fiber arrays. For this we carry out extensive viscous flow computations in various structured and un-structured fiber arrays. Two types of fiber arrays are considered; in the first, the fibers are assumed to be clustered in square or hexagonal packing. Simulations show that the effective permeability of such arrangements can be expressed by an empirical formula in terms of the intra- and inter-tow porosities. In the second case, we consider random fiber arrays which are generated through a Monte-Carlo process, starting from uniform square arrays or from regular arrays of fiber clusters. Up to 900 individual fibers are included in each simulation The results demonstrate that at high values of (φ), deviations from the uniform array result in a decrease of K eff . At lower porosity levels, the permeability shows a maximum at some intermediate value of the mean Nearest Neighbor Distance (dnndd ). It is shown that fully clustered fiber arrays have higher K eff than randomized ones; it is also shown that for these systems (K eff ) scales with the deviation of Ripley’s second order intensity function for the given microstructure from that of the Poisson distribution. Finally we propose a metric of the aggregation state of the fiber assembly which appears to correlate with the computed permeability.