CFD Modeling of the Flow of Resin into a Preform Mold of Natural
Transcription
CFD Modeling of the Flow of Resin into a Preform Mold of Natural
CFD Modeling of the Flow of Resin into a Preform Mold of Carbon Fiber Caelan Lapointe Ronald B. Bucinell, Ph.D., PE Introduction Results Fungal mycelia is proposed to be the core material in an Ecofriendly sandwich structure. Sandwich structures are composed of lightweight core materials sandwiched between two thin sheets of strong and stiff fibers infused with a binding resin. This type of construction increases bending strength and stiffness of the structure while minimizing its weight. The sandwich structure in this project is manufactured in pieces; a vacuum infusion process is used to impregnate a carbon fiber mat with resin, the impregnated mat is then placed on either side of the core material, and then the entire sandwich is cured. This study focuses on the optimization of the vacuum infusion process to make sure that the fiber mat is uniformly impregnated with resin. The vacuum infusion process was investigated numerically for two resins and two mold geometries using Star CCM+, a computational fluid dynamics (CFD) package. The modeling objective was to determine what infusion parameters produced the most uniform wet-out of the fiber mat. The level of wet-out was assumed to be correlated with the pressure distribution within the fluid as it flowed through the mold. Models generated for this research matched the experimental configuration used by researchers at RPI. Results will be comparted to experimental results and provide a theoretical foundation for mold geometries conducive to even resin infusion. Absolute pressure data were extracted and fit with a polynomial function in MATLAB to produce surfaces representative of the pressure distribution in the mold. Two figures were generated for each simulation to visualize the pressure distribution at the top and bottom of the mold. The mold with one inlet and one outlet produced a pressure distribution that was much more uneven than the mold with two inlets and two outlets, seen by comparing the vertical columns below. There was negligible difference observed between resins A and B. One Inlet, One Outlet Two Inlets, Two Outlets A CFD Investigation CFD is used to simulate fluid movement present in many real-world problems, ranging from vehicle drag analyses to full-scale wind farm modeling. CFD models are solved iteratively; continuity and conservation equations are satisfied within a discretized geometry for each iteration to arrive at a solution. All simulations were generated in Star CCM+ v9.04 for this project and run on a desktop computer. Porous media is modeled macroscopically using Darcy’s Law in Star CCM+ [1]. Regions within a geometry designated as porous impede fluid flow via a pressure gradient calculated with Darcy’s Law [1,2]. These regions were defined by viscous resistance parameters, dependent on fluid viscosity and permeability of the porous media, specified by the user. Simulations were created for two mold geometries that included porous regions and implemented practices specific to modeling vacuum infusion [1,2,3]. Mold geometries used in these simulations are shown below. Two different resins were also simulated. The resins had viscosities of 1100 centipoises (cp) and 470 cp respectively. Mold geometries are shown below; areas modeled as porous regions are outlined in blue. B Conclusions and Future Work This research investigated the vacuum infusion of a carbon fiber preform. The impact of mold geometry and resin viscosity on resin infusion, with the goal of wet-out and an even pressure distribution within the mold. CFD simulations utilizing Darcy’s Law and practices common to modeling vacuum infusion were created in Star CCM+ to simulate resin flow through a fiber preform. Two mold geometries and two resins were modeled. Simulation results will provide a theoretical foundation for the creation of molds conducive to even resin infusion through porous media. Results will be compared to experimental results obtained by researchers at RPI. The methodology developed for this research and techniques used to model vacuum infusion accurately can be applied to model more complex geometries in the future. References 1. 2. 3. Star CCM+ Tutorial Guide. Porous Resistance: Isotropic Media. (PDF). Star CCM+ Documentation. Isotropic Resistance Using the Ergun Equation (Forchheimer for Packed Beds). (PDF). Song, X. Vacuum Assisted Resin Transfer Molding (VARTM): Model Development and Verification. Ph.D. Dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA, 2003 (PDF). Acknowledgements 1. 2. 3. 4. 5. Ronald Bucinell, Ph.D., PE Robert Rizollo, Ph.D. candidate at RPI Daniel Walczyk, Ph.D., PE, Faculty at RPI Harish Gopalan, Ph.D. Jeffrey Doom, Ph.D.