Flow Analysis with Fiber Preform Deformation During Compression Resin Transfer Molding

Merotte, Justin
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University of Delaware
Compression resin transfer molding (CRTM) is an alternative solution to conventional resin transfer molding processes. It offers the capability to produce net shape composites with fast cycle times making it conducive for high volume production. The resin flow during this process can be separated into three phases; (i) metered amount of resin injection into a partially closed mold containing dry fiber preform, (ii) closure of the mold until it is in contact with the fiber preform displacing all the resin into the preform and (iii) further mold closure to the desired thickness of the part compacting the preform and redistributing the resin. Understanding the flow behavior in every phase is imperative for predictive process modeling that guarantees full preform saturation within a given time and under specified force constraints. In this thesis, the CRTM flow is modeled as a two dimensional flow in a gradually deformed porous medium during all three phases. The governing equations are formulated and coupled with the constitutive equations that describe the deformation and permeability behavior. Due to the non-linear nature of coupled system of equations, a numerical solution is developed that describes the flow front progression and the preform deformation during the process. A non dimensional analysis is conducted in which the applied force and initial gap size emerge as the important process variables that influence the process cycle time. Limiting cases are identified which reduce the flow to one dimensional flow for which a simplified solution is developed. The results are verified using an experimental setup whichapplies a constant force to the preform in a transparent mold allowing one to track the flow front. This study quantifies the effect of preform deformation due to the fluid pressure and should prove useful in applications that involve fluid impregnation in deforming porous media.