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- Frishfelds, Vilnis, et al.
(författare)
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Permeability of clustered fibre networks : modelling of unit cell
- 2003
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Ingår i: Mechanics of composite materials. - 0191-5665 .- 1573-8922. ; 39:3, s. 265-272
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Tidskriftsartikel (refereegranskat)abstract
- The paper is focused on estimating the permeability of a clustered fiber network by variational methods. First, a laminar flow in ducts is considered by using polynomial trial functions. Then, a longitudinal flow through a square array is described by expanding the flow-rate field in trigonometric and Laurent series. Finally, a formal scheme for estimating the longitudinal permeability in a cluster with an irregular distribution of fibers is given. The irregular distribution is modeled by setting an individual effective radius for each fiber and then letting this fiber reach its minimum gravitational energy. The results obtained here form a basis for future predictions of the permeability of fibrous reinforcements.
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| 2. |
- Lundström, Staffan, et al.
(författare)
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A statistical approach to permeability of clustered fibre reinforcements
- 2004
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Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 38:13, s. 1137-1149
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Tidskriftsartikel (refereegranskat)abstract
- The focus is set on mesoscale modelling of permeability of real fabrics used in composite manufacturing. Of particular interest is the effect of expected perturbations from perfect geometries, such as fibre bundle crimp, on the permeability. To start with, variational methods are used to calculate the perme-ability of individual gaps between fibre bundles. Based on this study a network of unit cells is formed enabling studies of two- and three-dimensional flow through the structure. From such an analysis the overall permeability of an arbitrary distribution of unit cell permeabilities can be calculated. Here random and controlled distributions are simulated. The former is an approximate representation of a continuous strand mat and the latter may describe Non-Crimp Fabrics. The result is that for random distributions, the permeability decreases with the maximum variation in unit cell while for a controlled permeability distribution the overall permeability can as well increase as decrease depending on the type of perturbation. In both cases the type of flow: one-, two- or three-dimensional strongly influence on the quantitative result. Hence, for the type of fabrics studied, it is necessary to model the full 3D-flow through to get a correct permeability value.
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