PPA: Preform Property Analysis
Simulations
Index (at Interactive Learning Tools subsite)
This program can be used to assist in the design and analysis
of the mechanical properties of preforms for resin transfer
molding. The preforms may be constructed with various
combinations of random mats, fabrics, and cores. The program
provides the effective properties of the selected assembly.
Thermal and mechanical loadings can be imposed and the
resultant point-wise stresses evaluated.
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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
The computations are based on classical laminated plate theory,
which requires that each layer obey linear stress-strain
relationships and that an approximate state of plane stress
exists within the assembly.
Features
The introductory page describes the program and presents the user with three
options: Tutorial (which reviews lamination theory and introduces
nomenclature), Theoretical Basis (which summarizes the
theoretical aspects and provides reference sources), and
Computation.
Selection of the Computation option leads to a page that allows the
user to choose the preferred set of units, the resin system that will be
used to infuse the preform, and the total number of layers in the
preform assembly. The next page allows the user to select the type of
fiber (glass, carbon, or aramid) that will be used for each layer.
When the fiber has been selected, a screen appears to provide
choices for the fabric type. A sample of this page is shown here for
glass fibers. A similar page can be accessed for the selection of
core materials such as balsa wood or foam core.
Each layer can be assigned distinct orientations with respect to a
reference direction. This process is repeated until the
preform has been assembled. The user can specify forces and
bending moments to be applied to the structure to interrogate
the behavior of the cured preform under mechanical loading. The
temperature difference can be specified to examine behavior as
the structure undergoes temperature excursions. The user may
select tabular modes of display for a variety of the
characteristics that govern the tensile and bending
behavior of the structure. Graphical displays of the
stress or strain distribution throughout the thickness can be
selected. The figure below shows a typical output.
Help buttons are provided on the various pages that display the
relevant portion of the tutorial related to each page.
Applications
This program can be used to predict the overall effective thermoelastic
properties of the structure:
- Young's moduli--E11, E22, E33
- Shear moduli--G12, G13, G23
- Poisson's ratios--n12, n13, n23
- Coefficients of thermal expansion--a11, a22, a33
The stiffness behavior of the structure as characterized by the
ABD matrices can be displayed. Point stresses or strain
distribution throughout the thickness can be obtained in graphical or
tabular form.
The preform property analysis can be conducted for various materials
or layer sequences to aid in selecting the preform architecture
for an application requiring certain mechanical loading or thermal cycling.
Prof. John W. Gillespie Jr.
phone: 302-831-8702
fax: 302-831-8525
e-mail: gillespie@ccm.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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