Permeability quantifies the conductance of technical textiles for resin flow and is therefore crucial for designing processes for manufacturing of continuously fiber reinforced composites. Today, large experimental test programs are required for characterization of permeability. Together with Math2Market GmbH, the IVW dealt with the development of a novel simulative-experimental approach, using experimental tests to calibrate a simulation model for replacing a significant amount of the experimental tests through “virtual” measurements.
Three basic routes were followed: At first a µCT-scan of a glass fiber non-crimp fabric was directly fed into GeoDict, the material simulation software developed by Math2Market GmbH. Second, a digital twin of the textile was created by computer modelling of basic structure and subsequent virtual compaction. µCT-model and digital twin were then used for computational fluid flow simulation which gives the direction-dependent permeability as an output. Third route was the experimental permeability measurement to generate reference values. Comparing the results of all three routes allows statements about the functionality of the simulation and accuracy of modelling.
Good correlation between the results of experiments and µCT-model based simulations show that the numerical computation of permeability with GeoDict is realistic. With 15 - 82 % deviation from the experimental results which show an average standard deviation of 25 %, the digital twin shows a better correlation than the µCT-model and shows high potential for substitution of experiments. Hence, the digital twin reflects real textile structure quite well. This is mainly accounted to the virtual compaction step, which takes various imperfections such as yarn deformation and varying nesting behavior into account. Even better results are expected when in a next step an anisotropic permeability will be allocated to the yarns. The simulative-experimental approach includes the specification of an experimental plan for calibration of the simulations in a defined fiber volume content range.