On the stochastic variations of intra-tow permeability induced by internal geometry variability in a 2/2 twill carbon fabric

This study investigates the stochastic variation of tow cross sections in a 2/2 twill carbon fabric and intra-tow permeability. A large sampling of tow cross sections (720 per layer) done by X-ray Micro-Computed-Tomography of a 7-layer composite plate is used to validate the use of the following statistical distributions of the random geometrical parameters: tow thickness (normal), tow width (log-logistic), intra-tow fibre volume fraction (log-normal) - and intra-tow permeability (gamma). The intra-tow fibre volume fraction and permeability variables are auto-correlated with a correlation length of ca. 3 mm, which corresponds to a correlation length of the out-of-plane tow centroid coordinates and is close to the spacing of the warp and weft yarns. The findings can serve as guidelines in doing Monte Carlo modelling of woven preforms variability and continue previously published work on inter-tow geometry and permeability.