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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
SECTION 2
Solid Composites
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
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s33 interlaminar normal stress (peel stress) and s31 , s32 interlaminar shear stresses are important in the study of
delamination
3
Shell vs. Solid Composite Elements
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
A few solid composites examples
Stringer/Skin
delamination
Bolted Joint Tension and Compression
test coupons
Scarf Repair
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Create the 3D Orthotropic Material
1. Create the 3D orthotropic material
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Create the 3D Orthotropic Material
Anisotropic material relationships (from Nastran 2011 Linear Static Analysis Users Guide):
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Create the 3D Orthotropic Material
Orthotropic material relationships (from Nastran 2011 Linear Static Analysis Users Guide):
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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.
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Defining the Composite Layup
Two ways to specify ply thickness
1) Enter as a percentage of total laminate thickness
2) Enter actual ply thickness
(1)
% of laminate thickness
(2)
Actual ply thickness
or
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
Thickness
Direction
CHEXA Element
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.
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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.
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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.
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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 z-axis
2
1
3
xm
ym
zm
xc
yc
zc
Coord 10001
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Element coordinate systems plotted
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Defining the solid laminate property
Define the thickness direction
Also known as layer direction
X
Y
Z
Element coordinate
system
ply
ply
ply
ply
ply
ply
ply
ply
ply
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Defining the solid laminate property
Tip: Use the element coordinate system plot to help you
select the thickness direction
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
SOL 400 Solid Composites
Nastran entries generated by Patran
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
(1)
(2)
(3)
Averaged
Averaged
Un-averaged
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Solid Shell Composites
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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.
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Solid Composites Types
Each layer has 1 integration
point
Maximum of 2040 layers per
element
Defined by PCOMPLS
INTi = ASTN
The thickness direction must be in the element Z direction
1
3
2
One integration point per layer
Solid Shell Composites
Each layer has 4 integration points
Maximum of 510 layers per element
Defined by PCOMPLS INT8=L or INT20=Q
2
1
3
2
Solid Layered Composites
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
Solid Shell
Composite
Must be set
to Element Z
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
3
2
1
zm
ym
xm
xc
yc
zc
Coord 10001
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Defining Solid Shell Composites
Nastran entries produced by Patran
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
(1)
(2)
(3)
Averaged
Un-averaged
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
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
Tips Enhanced Transverse Shear
V
t
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Tips Generating Solid composite elements
Sweeping
Meshing
Solids
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)
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
Laminate Modeler
Extrudes shell mesh into solid composite elements
Automatically creates PCOMPLS
Can split laminate into multiple layers of solids
Tips Generating Solid composite elements
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Composites Technology Day, February 2012
Copyright 2012 MSC.Software Corporation
End of Section 2