Permeability enhancement with different glass fiber quasi-UD structure arrangements for RTM-TP process

International audienceThree different types of a quasi-unidirectional fabric have been produced and studied in order to reach the objective of the enhanced longitudinal permeability. The overall goal of the project TAPAS is to use the optimised fabric in a RTM process adapted to high fluidity polyamide 6,6. Microstructure study is undertaken with Scanning Electron Microscope (SEM) and X-Ray Tomography (X-RT) images as well as image treatment by stereology. Permeability has been measured experimentally and estimated by an analytical model based on Kozeny-Carman relationship and by the inverse identification with the help of the Brinkman equation numerically solved by the Proper Generalized Decomposition method (PGD) and finite elements (FEM). Both models for the prediction of permeability seem to give comparable results, whereas experimental values of permeability are quite higher than model ones. The fact that both models give predictions with the help of 2D cut images should explain this discrepancy with experiments. Nevertheless, the same increasing trend in permeability for the three fabrics is observed both on experimental and analytical model values. Finally, an example of RTM-TP composite plate with PA6,6 and the most permeable fabric among the three, at a volume fraction of 54.2%, is given as a proof of concept. © 2015 International Committee on Composite Materials. All rights reserved

Permeability enhancement with different glass fiber quasi-UD structure arrangements for RTM-TP process

International audienceThree different types of a quasi-unidirectional fabric have been produced and studied in order to reach the objective of the enhanced longitudinal permeability. The overall goal of the project TAPAS is to use the optimised fabric in a RTM process adapted to high fluidity polyamide 6,6. Microstructure study is undertaken with Scanning Electron Microscope (SEM) and X-Ray Tomography (X-RT) images as well as image treatment by stereology. Permeability has been measured experimentally and estimated by an analytical model based on Kozeny-Carman relationship and by the inverse identification with the help of the Brinkman equation numerically solved by the Proper Generalized Decomposition method (PGD) and finite elements (FEM). Both models for the prediction of permeability seem to give comparable results, whereas experimental values of permeability are quite higher than model ones. The fact that both models give predictions with the help of 2D cut images should explain this discrepancy with experiments. Nevertheless, the same increasing trend in permeability for the three fabrics is observed both on experimental and analytical model values. Finally, an example of RTM-TP composite plate with PA6,6 and the most permeable fabric among the three, at a volume fraction of 54.2%, is given as a proof of concept. © 2015 International Committee on Composite Materials. All rights reserved

Benchmark exercise on image-based permeability determination of engineering textiles: Microscale predictions

Permeability measurements of engineering textiles exhibit large variability as no standardization method currently exists; numerical permeability prediction is thus an attractive alternative. It has all advantages of virtual material characterization, including the possibility to study the impact of material variability and small-scale parameters. This paper presents the results of an international virtual permeability benchmark, which is a first contribution to permeability predictions for fibrous reinforcements based on real images. In this first stage, the focus was on the microscale computation of fiber bundle permeability. In total 16 participants provided 50 results using different numerical methods, boundary conditions, permeability identification techniques. The scatter of the predicted axial permeability after the elimination of inconsistent results was found to be smaller (14%) than that of the transverse permeability (~24%). Dominant effects on the permeability were found to be the boundary conditions in tangential direction, number of sub-domains used in the renormalization approach, and the permeability identification technique