Influence of fibre distribution on the transverse flow permeability in fibre bundles

For simulations of resin flow in fibre reinforced composite materials, Darcyʹs law is often applied. It is dependent on the permeability of the fibre architecture. For an in-depth understanding of the filling process of large and complex fibre architectures, the knowledge of mechanisms in the microscopic scale (in the order of magnitude of fibres and fibre tows) is essential to achieve complete impregnation of architectures of individual fibres. In this work, the influence of the fibre distribution characteristics on the transverse permeability in the microscopic scale was examined. The Morishita algorithm was applied to quantify the regularity of the fibre arrays. 2-D finite element models of 15 fibres with different distribution characteristics (decreasing regularity in fibre arrangement) were created, and CFD simulations were carried out to determine the permeability. It was found that permeabilities decreased with increasing "disorder" of the fibre distribution. With decreasing order in the arrangement, the gaps between the fibres become small, which decreases permeability. At the same time, the probability of appearance of flow channels by enlarged fibre gaps, increasing the permeability, is enhanced. Both mechanisms superimpose with each other leading to a decreased gradient of the decreasing permeability.