MFS: Mold Filling Simulation
Simulations
Index (at Interactive Learning Tools subsite)
This simulation program is designed to illustrate important
issues involved in infusing preforms during the resin transfer
molding process. Sample molds are used in an adaptive environment
to explore variations in gate location, mold pressure, resin
viscosity, and preform permeability. Graphical outputs show
the progress of the flow fronts for variations of these factors.
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This work was conducted
in a joint effort between the University of Delaware and Michigan State University
under the aegis of the National Science Foundation project
"Manufacturing Education and Training Program in Composite
Materials for the DoD and Durable Goods Industries" as part
of the DARPA Supplementary Education Awards.
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Background
Darcy's law may be used to relate volumetric flow rates to mold geometry,
mold pressure, resin viscosity, and preform permeability. Preforms are
usually assembled by stacking together several plies of mats and/or fabrics.
Open-weave fabrics have a higher porosity and permeability and are easier to
infuse than tightly woven fabrics. However, closed-weave fabrics provide higher
stiffness and strength. Depending on the weave pattern, the permeability of a
ply in the lateral direction may differ from that in the transverse direction.
This anisotropy complicates the analysis of the infusion process. Another
variation (called racetracking) arises due to gaps between the preform and
mold surface. These process variations and complex mold geometries can be
treated through finite element analyses. The results displayed in this
simulation were generated by a comprehensive program called Liquid Injection
Molding Simulation (LIMS). Further information concerning various applications
for this program may be obtained from the above contact.
Features
The introductory page describes the program and presents the user with three
options: Tutorial (which elaborates on the issues involved in mold filling),
Theoretical Basis (which summarizes the theoretical aspects and provides a
reference source), and Computation. Selection of the Computation option
leads to the page shown below.
The animation panels allow the user to fast forward, pause, rewind, etc. as
well as change animation speeds. The flow front is displayed at various times
shown below the figure.
The selection menu for Mold provides the user with an option for two mold
geometries: a simple flat plate and a complex shape (shown here). The pulldown
menu for Injection Location allows the user to choose three different pre-set
locations for the inlet gates. The Permeability pulldown menu allows the user
to explore changes in the relative permeabilities in the lateral (x) and
transverse (y) directions. The Racetracking option enables investigation of
the influence of racetracking on the flow front shapes and filling times.
The injection pressure can be varied between 1 and 10 bar and the viscosity
between 10 MPa and 500 Pa. After the selections have been made, the Apply Changes
button activates the animation sequence.
Applications
An important application of this simulation is the identification of vent locations.
Vents should be located in the last area to fill, in order to prevent air entrapment
and "dry spots." This simulation can be used to illustrate how the various factors
can influence the location of vents.
The time to fill the mold is an important process parameter. This simulation can be
used to explore how each factor influences the mold filling time and identify the
critical factors.
LIMS, a comprehensive program, is capable of treating
complex geometries and preform structures.
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phone: 302-831-8975
fax: 302-831-8525
e-mail: advani@me.udel.edu
Center for Composite Materials
201 Composites Mfg. Science Lab
University of Delaware
Newark, DE 19716-3144
phone: 302-831-8149
fax: 302-831-8525
e-mail: info@ccm.udel.edu
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