Résumé
In liquid composite molding processes, the impregnation of the fibrous preform, composed of a double pore scale, is a crucial challenge [1]. As a matter of fact, a poor impregnation can lead to the void formation (micro or macro voids), and this can also affect the surface and interface quality as well as the mechanical properties of the final parts [2]. To avoid these defects, numerical simulation is an important tool for manufacturers to predict the impregnation of the fibrous preform during the process. Therefore, the experimental characterization of the permeability values of the fibrous preform is an important input data for the models. Furthermore, the multiscale structure of the fibrous preform leads to a dual scale flow of the liquid (between the tows or inside the tows) [3]. Consequently, to conduct simulations as close as possible to the reality, permeability values at different scales (fibrous preform and tow) are required. Another aspect aborded in this work, often neglected in the literature, is the effect of the affinity between the fluid and the fiber (capillary pressure [4]) on the permeability values at both scales. According to the literature, the capillary pressure can modify the unsaturated permeability under certain conditions, such as process parameters and affinity fluid/fiber [5].The aim of this study is to evaluate the impact of the surface modification of a basalt fabric on the in-plane permeability at two scales: the tow and the fibrous preform. Unsaturated (Kunsat) and saturated (Ksat) permeability experiments were performed at the fibrous preform scale whereas only saturated permeability experiments were performed at the tow scale (Figure 1). The basalt fabric was modified by thermal treatment. The test liquids use for the study were water, a polyethylene glycol (PEG300) and a silicone oil (PMX200 – 100cS). First results showed, at the single fiber scale, that the thermal treatment modified significantly the surface energy of the basalt fiber by increasing the total surface energy and particularly the polar component [6]. At the fibrous preform scale with water, results showed an increase of the saturated and unsaturated in-plane permeability after thermal treatment (Table 1). The experiments with the polyethylene glycol and the silicone oil are currently carried on for the thermal treated fabric. These results, combined with results at the tow scale, will allow us to improve the understanding of considering the capillary effects in the unsaturated permeability and to include these values in simulation at higher scale [7].