sec2 solid composites 021712

S2-1

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

S3-2

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

S2-3



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

S2-4



A few solid composites examples

Stringer/Skin

delamination

Bolted Joint Tension and Compression

test coupons

Scarf Repair

S2-5



Create the 3D Orthotropic Material

1. Create the 3D orthotropic material

S2-6




Anisotropic material relationships (from Nastran 2011 Linear Static Analysis Users Guide):

S2-7




Orthotropic material relationships (from Nastran 2011 Linear Static Analysis Users Guide):

S2-8




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

S2-9



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.

S2-10




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

S2-11




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.

S2-12



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.

S2-13




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.

S2-14




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

S2-15



Element coordinate systems plotted


The element coordinate system option (CORDM = -1) is useful here if the element coordinate systems are aligned

appropriately as shown below:

Set to -1

S2-16




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

S2-17




Define the thickness direction

Also known as layer direction

X

Y

Z

Element coordinate

system

ply

ply

ply

ply

ply

ply

ply

ply

ply

S2-18




Tip: Use the element coordinate system plot to help you

select the thickness direction

S2-19



SOL 400 Solid Composites

Nastran entries generated by Patran

S2-20



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

S2-21



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

S2-22



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

S2-23



Solid Shell Composites

S2-24



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.

S2-25



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

S2-26



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

S2-27



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

S2-28




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

S2-29




Nastran entries produced by Patran

S2-30



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

S2-31



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

S2-32



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

S2-33



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)

S2-34



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

S2-35



End of Section 2

sec2 solid composites 021712

Documents

composites technology

actual ply thickness

actual thickness

element thickness

laminated composites

software corporation

solid composite elements

d orthotropic material