| Features
to Look for in FEA Software for Composite Analysis |
Composite materials analysis imposes a number of requirements
that are significantly different when compared to isotropic
materials and FEA software used for composite analysis must
be designed to handle the anisotropic nature of composites and
the failure mechanisms associated with their properties like
cracks, delaminations, and fiber failure. In addition, high
quality FEA software should include features that make it easy
to use while providing the engineer with the power to get results
that are practical and truly valuable for application to real
world problems. NEi
Nastran fills this need for composite designers with
a number of features in model creation, material definition,
meshing, post processing, failure criteria, and data presentation.
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User
friendly definition of material properties. Clear, easy
input of strength and stiffness terms with access to material
libraries.
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Definition of
ply lay-up. Stacking sequences can be quickly and easily
entered into a table, and symmetry can be used to reduce entries.
Modification and changes are easily made and the chance of error
is greatly reduced.
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Easy orientation
definition. Curved surfaces can complicate the orientation
of fibers. NEiNastran can project a cylindrical or spherical coordinate
system onto a structure to get good representation of ply orientation.
Advanced application can carry out draping analysis with NEi Laminate
Tools if this degree of fidelity is required. |
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Outer mold line
representation.
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Post processing
visualizations that pinpoints problem areas. Enormous amounts
of data can be involved in multi lay-up and multi ply structures.
NEi Nastran provides a logical
path from stress analysis of a structure to Failure Index results
that can isolate problems and pinpoint them to definite regions
on specific plies.
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Failure Indices
and Strength Ratio. NEi Nastran
supports all the major composite failure analysis indices Tsai-Wu,
Hill, Hoffman. Plus NEi Nastran
includes the most modern forms of Puck and NASA Langley LARC02.
In addition, the Strength Ratio is available for easy linear scaling
and qualitative analysis.
NASA Langley has developed LARC02, a set of first-ply-failure
criteria which have shown to be accurate and physically consistent.
It is well suited for design purposes because it balances accuracy,
material characterization requirements, computational effort,
and ease of results interpretation.
| Advanced Failure
Criteria for Composites |
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LaRC02 Set of Criteria |
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Developed by NASA |
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First-ply-failure |
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Physically based |
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Hashin, Puck approach |
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No additional material properties required compared to Tsai-Wu |
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Failure mode taken into account |
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Extensive validation (WWFE) |
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| Stability Index Output
for Sandwich Structures |
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Theory based on Facesheet Wrinkling in Sandwich
Structures, NASA-CR-1999-208994, 1999 |
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Honeycomb
Sandwich Material Properties |
Material |
Modulus of Elasticity (msi) |
Tensile Limit (ksi) |
Compression Limit (ksi) |
Shear Limit (ksi) |
Aluminum Face Sheets |
10.0 |
35.0 |
35.0 |
23.0 |
Honeycomb Core |
0.1 |
0.1 |
0.3 |
0.2 |
Bonding Material |
- |
- |
- |
0.1 |
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Honeycomb
Sandwich Material Properties |
For more information see "Finite
Element Implementation of Advanced Failure Criteria for
Composites ".
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3D CAD Models.
NEi Nastran Modeler imports models
from all major CAD systems. For SolidWorks users, NEi Works
is embedded, completely eliminating the need to import files.
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Sensitivity and
Configuration Trade Off Studies. NEi Nastran
Editor feature is perfect for composite analysis because it
provides an easy inexpensive way to do sensitivity and configuration
trade off studies.
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Features tabbed windows to give immediate access
to all input and output files |
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Field markers make manual editing simple and increase productivity
dramatically |
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Complete online documentation and context sensitive help |
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Permits batch queuing of jobs for sensitivity and configuration
trade studies |
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Special real time controls allow changing solution parameters
while running |
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Real time 2D xy-plotting and 3D deformed shape and contour
plotting |
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PPFA Progressive Ply Failure Analysis allows engineers to examine composite structural behavior beyond first ply failure. Reduce weight and material costs while saving time in analysis by efficiently analyzing residual strength, local damage effects, temperature effects, post-FPF (First Ply Failure) events, separation, ultimate failure, design modifications, and ultimate strength with PPFA. |
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