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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
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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
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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.