Injection flexible dans moule isotherme: Conception et analyse d'un nouveau procede de fabrication de composites

This research project involves the study of a novel technique of liquid composite moulding (LCM), in which the main goal is to perform mass production of high performance composites.;The objective of this work consists of designing a Polyflex mould and analyzing the effects of the various process parameters with a series of experiments. Injection pressures are kept constant and the manufacturing process is isothermal. More precisely, the goal of this research is to determine the influence of five manufacturing parameters on the total filling time and resin flow velocity. The compaction pressure, injection pressure, compaction fluid viscosity, injected resin volume, and fibre volume fraction. A transparent mould was designed and built in which the rectangular cavity could be adjusted for different thicknesses. The fluid used for fibre filling and as compaction liquid has been silicone oil, for various gauged viscosities. A continuous filament mat was selected as reinforcement. A two-level factorial experimental design was built in order to analyze the results.;The pressure of the compaction fluid is the most important parameter that governs the total filling time. A higher compaction pressure results in faster resin flow at the beginning of the compaction stage. Just after the compaction fluid flow front overpasses the resin flow front, the resin flow velocity starts to decrease. Compared to the RTM ("Resin Transfer Moulding") process, a significant reduction of filling time (76%) can be observed for the fabrication of a composite plate of thickness 1,76 mm and 20% fibre content. This new process brings about a considerable potential of improvement in order to reduce manufacturing cycle time for the production of high performance composites. This is especially welcome for automotive applications, in which composite parts must be produced in high volume to be competitive. Future work involves process modeling and optimization of the various manufacturing parameters that govern mould filling.;This new process, called Polyflex, is mainly characterized by the use of a rigid mould in which the cavity is divided into two sealed chambers separated by a plastic film. This new approach works as follows: in the lower chamber, where the fibrous reinforcement is located, a given quantity of resin is injected, then the upper chamber is filled up with a fluid that is used to facilitate the filling of the lower cavity and compact the composite. Besides reducing manufacturing cycle times compared to other LCM processes, Polyflex technology makes it possible to control the fibre volume fraction by monitoring the volume of resin injected.