Étude et prédiction numérique des modes d'écoulement à travers un renfort fibreux à double échelle de porosité

Composite materials manufactured by Liquid Composite Molding processes (LCM) are increasingly used in industry. One of these methods is Resin Transfer Molding (RTM) which consists of injecting a liquid reactive resin through a fibrous reinforcement. Successful implementation of this process requires a clear understanding of the different flow modes during the injection as well as a thorough knowledge of the porous fiber bed properties. To limit the generation of manufacturing defects during processing, the impregnation mechanisms driven by viscous or capillary forces can be studied either experimentally or through numerical simulations. The main objective of this project is to numerically reproduce classical characterization tests such as capillary rises and permeability measurements using an original approach based on a cellular discrete representation of the fibrous structure. Results from previous work indeed suggest that this technique is promising, but an in-depth study must be conducted. To reach that goal, the present work generalized a filling code with free surface flow to the 3D case. Firstly, cellular models are obtained using a method based on a voxel representation of the textile fabric. The approach requires an experimental characterization of the reinforcement specific dimensions. This step provides the input data to numerically model the reinforcement geometry using an idealized volume representation. This geometric model is then voxelized in an optimum manner. Finally, an algorithm is developed to create computing cells for finite difference approximation, which represent the fibrous reinforcement from the voxelized model. Several parameters are used to describe the material included in the volume of the different cells. The main parameter is a tensor giving the permeability in the three spatial directions which depends on the effective fiber volume content in each direction. The second part of the work consisted of developing a three-dimensional mold filling code including a free surface to represent the flow front. The constitutive laws implemented are Darcy's law and the principle of mass conservation. The code allows simulating capillary rise and permeability experiments.