Co-authors​ :

 Romain RAVEL (FRANCE), Monica PUCCI (FRANCE), Pierre-Jacques LIOTIER (FRANCE) 

Composite materials have been increasingly used in energy and transport sectors, as they enable manufacturing of lighter parts with complex shapes in a single processing operation. Liquid Composite Moulding (LCM) processes are currently used in these sectors, and one of the major challenges for manufacturers is to ensure the perfect impregnation of the fibrous preforms to avoid any defect formation. In parallel, it is necessary to optimise numerical models to obtain impregnation simulations as close as possible to the reality of the process. An important parameter that can be determined experimentally is the permeability of the fibrous preform. The permeability is defined as an intrinsic parameter of the porous medium and defines its ability to allow a fluid to flow through it. It depends on the porous medium morphology composed of a double pore scale (intra-tows and inter-tows pores), as well as on the fluid-fiber physico-chemical interactions during the process [1]. Permeability can be estimated when the mould is filled with liquid, named as saturated permeability or when the fluid is filling the mould, that is the unsaturated permeability [2]. In the literature, many studies already highlighted the influence of capillary effects on the impregnation of the fibrous preform and particularly on the void formation during the process [3].
In a previous study [4], the influence of the surface modification of basalt fibers on the wettability properties of the fabric has been assessed at different scales (thanks to surface energy determination, capillary wicking tests and permeability measurements). This study was performed using the water as test fluid due to its practicality and chemical affinity with the high polar surface of the modified basalt fibers. The results showed an increase of the unsaturated permeability after fiber surface modification. However, in order to be representative of resins used in LCM processes, it is important to choose a test liquid with similar physico-chemical properties of those of resins (such as viscosity and surface tension).
Consequently, the aim of this work is to evaluate the effect of the fluid nature on the characterised unsaturated permeability and capillary wicking of a basalt fabric. To do this, viscosity and surface tension measurements were performed on several liquids and a polyethylene glycol (PEG) and a silicone oil [5] were selected as test liquids to substitute the epoxy resin. The epoxy resin will also be tested as a reference. Capillary wicking tests will be performed to determine an equivalent capillary pressure in spontaneous impregnation with the basalt fabric for each liquid. Next, saturated and unsaturated permeability measurement will be performed. The final aim is to assess the effect of fluid-fiber interaction during impregnation, comparing the capillary pressure and the permeability results with each liquid and then to find the best candidate to represent the epoxy resin.