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This study addresses the issue of whether or not a normal distributionappropriately represents permeability variations. To do so, (i) thedistribution of local fibre volume fraction for each tow is experimentalydetermined by estimation of each pair of local areal density and thickness,(ii) the Kozeny-Carmen equation together with the change of variable techniqueare used to compute the PDF of permeability, (iii) using the local values offibre volume fraction, the distribution of local average permeability iscomputed and subsequently the goodness of fit of the computed PDF is comparedwith the distribution of the permeability at microscale level. Finallyvariability of local permeability at the microscale level is determined. Thefirst set of results reveals that (1) the relationship between the local arealdensity and local thickness in a woven carbon-epoxy composite is modelled by abivariate normal distribution, (2) while fibre volume fraction follows a normaldistribution, permeability follows a gamma distribution, (3) this work alsoshows that there is significant agreement between the analytical approach andthe simulation results. The second set of results shows that the coefficient ofvariation of permeability is one order of magnitude larger than that of fibrevolume fraction. Future work will consider other variables, such as type offabrics, the degree of fibre preform compaction to determine whether or not thebivariate normal model is applicable for a broad range of fabrics.

Probability density function of in-plane permeability of fibrous media: Constant Kozeny coefficient