SECTION 2
Solid Composites
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Shell vs. Solid Composite Elements
• Traditionally laminated composites are modeled
as shell elements in Nastran
• When a laminate is thick or when the load path
and state of stress in the structure is three
dimensional, solid elements are more
appropriate
3
s33 interlaminar normal stress (peel stress) and s31 , s32
interlaminar shear stresses are important in the study of
delamination
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SOL 400 Solid Composites
• Solid Composite Elements
–
–
–
–
Available in SOL 400
Composite layup definition directly assigned to solid elements
Stress recovery for ply stresses and interlaminar stresses
Supports progressive ply failure analysis
Composites Technology Day, February 2012
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A few solid composites examples
Scarf Repair
Stringer/Skin
delamination
Tension and Compression
test coupons
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Bolted Joint
S2-4
Create the 3D Orthotropic Material
1. Create the 3D orthotropic material
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Create the 3D Orthotropic Material
•
Anisotropic material relationships (from Nastran 2011 Linear
Static Analysis User’s Guide):
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Create the 3D Orthotropic Material
•
Orthotropic material relationships (from Nastran 2011 Linear
Static Analysis User’s Guide):
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Create the 3D Orthotropic Material
• A tape material is defined in the
coordinate system shown:
• Typically n13 is provided in data
sheets. For example n13 = 0.33
• Nastran wants you to enter n31
• Recall that
• n31 = n13 x (E3/E1) = 0.018
A common mistake is to enter the n13
value into this form
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Defining the Composite Layup
2. The next step is to define the laminate layup. This process is very
similar to the shell element laminate setup.
•
•
In Patran, click on the composite laminate icon to bring up the form.
Enter the thickness and orientation of each ply
The ply thickness can be entered either as the actual thickness, or as a
percentage of the total laminate thickness.
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Defining the Composite Layup
•
Two ways to specify ply thickness
1)
2)
Enter as a percentage of total laminate thickness
Enter actual ply thickness
(1)
(2)
Actual ply thickness
% of laminate thickness
or
Composites Technology Day, February 2012
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Defining the Composite Layup
•
Tips on entering ply thickness
1) Enter as a percentage of total
laminate thickness
– All percentages must add up to 100
– Nastran run will fail if the percentages do not
add up to 100
2) Enter actual ply thickness
– Make sure the ply thicknesses you enter
sum to a total laminate thickness which
equals to the element thickness. Nastran
will not check this for you.
– Behind the scene, Nastran divides the ply
thicknesses by the total laminate thickness
to compute fractions and use them to fit the
plies inside the element in parametric space.
Thickness
Direction
Composites Technology Day, February 2012
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CHEXA Element
S2-11
Defining the solid laminate property
3. The last step is to create a solid laminate property and assign it to
solid elements.
•
•
In Patran, click on the Solid property icon.
Set the option to Laminate.
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Defining the solid laminate property
3. Create a solid laminate property (cont.)
•
Specify the material orientation coordinate system
•
It is used to define the X, Y, Z directions for the
orthotropic material property defined earlier.
•
The default is the basic coordinate system.
Composites Technology Day, February 2012
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Defining the solid laminate property
• Specify the material orientation coordinate system
– This coordinate system directly defines the local material coordinate
system. No projection is used.
– Positive q direction is defined using the right hand rule about the local zaxis
zc
yc
xc
Coord 10001
zm
ym
xm
3
2
1
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Defining the solid laminate property
•
The element coordinate system option (CORDM = -1) is useful
here if the element coordinate systems are aligned
appropriately as shown below:
Set to -1
Element coordinate systems plotted
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Defining the solid laminate property
3. Create a solid laminate property (cont.)
Define the thickness direction
•
This tells Nastran how you intend to orient the plies
inside the solid elements
Ply 1
Ply 2
Ply 3
•
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Defining the solid laminate property
•
Define the thickness direction
•
Also known as layer direction
Z
Y
X
ply
ply
ply
ply
ply
ply
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ply
ply
ply
Element coordinate
system
Defining the solid laminate property
• Tip: Use the element coordinate system plot to help you
select the thickness direction
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SOL 400 Solid Composites
• Nastran entries generated by Patran
Composites Technology Day, February 2012
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Solid Composite Results
• SOL 400 solid composites
results are available in the
MASTER/DBALL, not in the
XDB.
– Specify MASTER/DBALL in
Patran before the run
– After the run, attach Master
to access the results
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Review the .f06 file
• SOL 400 Solid Layered Composites results
– Stress and strain results for each ply are provided at 4 integration points
at mid-ply position
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Plotting Stresses in Patran
• Patran stress fringe plot
1) Select Result quantity
2) Select which layer
3) Select stress component
• Ply stress fringe plot fills the entire element
Averaged
Averaged
(1)
(2)
(3)
Un-averaged
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Solid Shell Composites
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Solid Layered Composites vs. Solid Shell
Composites
• Solid elements tend to be overly stiff in bending.
• Several layers of solid elements through the thickness are
typically required to correctly simulate a structural member
in bending.
• Solid composite elements have this same limitation. Solid
composite elements with this default formulation are called
Solid Layered Composite (or Regular Solid Composite)
elements.
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Solid Layered Composites vs. Solid Shell
Composites (Cont.)
• In cases where bending is dominant, and the model does
not have several layers of solid elements through the
thickness, consider using the solid shell formulation.
• In this formulation, assumed strain functions are added to
the elements to make them behave more like shell
elements when loaded in bending.
• Solid composite elements with this formulation are called
Solid Shell Composite elements.
Tip: Solid shell composite elements
are also known as continuum shell
composite elements
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
S2-25
Solid Composites Types
Solid Layered Composites
Solid Shell Composites
•
• Each layer has 1 integration
point
•
•
Each layer has 4 integration
points
Maximum of 510 layers per
element
Defined by PCOMPLS – INT8=L
or INT20=Q
• Maximum of 2040 layers per
element
• Defined by PCOMPLS
– INTi = ASTN
– The thickness direction must
be in the element Z direction
3
2
One integration point per layer
2
1
3
2
1
Composites Technology Day, February 2012
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Defining Solid Shell Composites
• To specify the solid shell composite element, the user needs to turn on
the assumed strain formulation. This is done by setting the integration
scheme to Assume Strain on the input properties form.
• The thickness direction must be set to Element Z Direction
Must be set
to Element Z
Solid Shell
Composite
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Defining Solid Shell Composites
• Define the material orientation coordinate system
– The x-axis of the specified coordinate system projects onto the element face
to create the local material x-axis
• Face “normal” to the element Z direction
–
–
–
–
–
The local z-axis is in the thickness direction
The local y-axis is obtained by the cross product ( local-z  local-x )
Positive q direction is defined using the right hand rule about the local z-axis
Thickness direction must be set to Element Z direction
This is very similar to the
way MCID is defined for the CQUAD4
z
c
yc
xc
Coord 10001
zm
ym
xm
3
2
1
Composites Technology Day, February 2012
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Defining Solid Shell Composites
• Nastran entries produced by Patran
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Review the .f06
• SOL 400 Solid Shell Composites results
– Stress and strain results for each ply are provided at one integration point
at mid-ply position
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Plotting Stresses in Patran
• Patran stress fringe plot
1) Select Result quantity
2) Select which layer
3) Select stress component
• Ply stress fringe plot fills the entire element
Averaged
(1)
(2)
(3)
Un-averaged
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Tips – Enhanced Transverse Shear
• Enhanced transverse shear distribution
– When modeling shell-like structures with a single layer of solid
elements, the TSHEAR (transverse shear) parameter can be
turned on to obtain a parabolic shear distribution through the
thickness of the shell
V
t
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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Tips – Generating Solid composite elements
• Methods for generating solid composite elements
1. If the geometry is hex-meshable, directly mesh the solids
2. If the geometry is not hex-meshable, mesh the solid face with
quads and sweep them into solid elements
3. Laminate Modeler can extrude solid composite elements from a
shell mesh (see next slide)
Sweeping
Meshing
Solids
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
S2-33
Tips – Generating Solid composite elements
• Laminate Modeler
–
–
–
Extrudes shell mesh into solid composite
elements
Automatically creates PCOMPLS
Can split laminate into multiple layers of solids
Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
S2-34
End of Section 2
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Copyright 2012 MSC.Software Corporation
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