Composite Finite Element Project 3.PDF

8/17/2019 Composite Finite Element Project 3.PDF

1/16

Ply Drop-off 1

22.514 1 REV. D.S 4/28/12

FEA of Composites – Ply Drop-off 3D Example 1

22.514

Instructor: Professor James Sherwood

Author: Dimitri Soteropoulos

Problem Description:

A three layer [0/90/0] graphite-epoxy composite laminate subjected to an axial load will be examined. A

finite element model will be constructed using Abaqus/CAE 6.10 where the principal stresses in the

respective plies will be analyzed.

Figure 1. [0/90/0] Laminate

Since the laminate shown in Figure 1 consists of ply drop-offs, the 3D solid element finite element model

will be constructed using three distinct plies. The respective material properties for the model areshown in Table 1.

Table 1. Graphite-Epoxy Material Properties

Figure 2. Ply Drop-off Sections

Material Property Value

E1 155.0 GPa

E2 12.10 GPa

12 0.248

G12 4.40 GPa

G13 4.40 GPa

G23 3.20 GPa


2/16

Ply Drop-off 1

22.514 2 REV. D.S 4/28/12

Creating the Model Geometry

A solid model with dimensions shown in Figure 2 will be created in Abaqus.

Figure 2. Dimensioned Cross Section

Open Abaqus/ CAE 6.10 by clicking Start -> Abaqus 6.10 -> Abaqus CAE.

Double click Parts in the model tree and create a part as shown below:

Click Continue…

Using the Create Lines: Connected tool, and the Add Dimension tool, draw the cross section of the ply

drop-off shown in Figure 2. To avoid over constraining the model, only add the dimensions shown in the

below figure. After completing the sketch the viewport should look similar to the figure below. PressF6

on the computer keyboard to auto-fit the cross section to the viewport. (Note: the number of decimals

on the dimensions tag may vary, for instance the 0.000150 m dimension might appear as 0, to change

this click the Sketcher Options tool in the module, click the Dimensions tab and change the number of

decimal places to whatever value you would like.)


3/16

Ply Drop-off 1

22.514 3 REV. D.S 4/28/12

Press Esc on the computer keyboard to exit the Add Dimension tool. Click Done to exit the Sketch

Mode. Enter a value of 0.005 under the depth option of the Edit Base Extrusion dialog box that appears

and click OK.


4/16

Ply Drop-off 1

22.514 4 REV. D.S 4/28/12

Partitioning the Model

Switch to the Part module in Abaqus by changing the dropdown at the top of the viewport from

Property to Part if not already there. Click the Create Datum Point: Offset From Point icon in the

module to two datum points at the corners shown in the figure below. Click the point and hit enter on

the keyboard (i.e no offset). Repeat this step two times to create both datum points. Make sure to clickthe correct points!!

While the Create Datum Point: Offset From Points tool is still activated click the top left point of the

structure. In the offset entry at the bottom of the viewport enter a 0.0,-0.000150,0.0 and click enter on

the keyboard. A new datum point will appear -0.000150 units down from the corner in the -y direction.

Next create another datum point which is offset -0.0003 units from the corner in the -y direction.


5/16


6/16

Ply Drop-off 1

22.514 6 REV. D.S 4/28/12

If the model is rotated, it can be seen that the partitions just created are exclusive to the particular

surface. It is desired for the partitions to extrude through the whole model in the z direction. Click the

Partition Cell: Extrude/Sweep Edges icon in the module. Click the edge shown in the figure below. (The

junction between the top and middle ply)

Click Done. Click Extrude along direction. Click any of the lines that are in line with the global z axis. Click

OK (if the arrow is pointing in the direction you want the partition to be extruded). Click Create

Partition. Rotate the model so that the partition truly extended through to the other side of the model.

Repeat the same steps for the other surface partition created. If both partitions have been createdcorrectly the other side of the model should look similar to the figure below.


7/16

Ply Drop-off 1

22.514 7 REV. D.S 4/28/12

Defining Material Properties

Double click Materials in the model tree and create a material as shown below. The material properties

can be found in Table 1 of the problem description. (Mechanical->Elasticity->Elastic) (Note: Material

Type Lamina can only be used with different mesh generation techniques, for this case we will just use

an isotropic material property since we are essentially using an auto mesh).

Click OK.


8/16

Ply Drop-off 1

22.514 8 REV. D.S 4/28/12

Creating a Composite Layup

Three separate composite layups will be created for this model, each representing a ply of the laminate.

In a composite layup the region, materials, ply orientation, and thickness will be assigned to the

geometry. This step is similar to creating and assigning a section for an isotropic material analysis.

Expand the Parts (1) entry in the model tree by clicking the + to the left of it. Further expand the modeltree by clicking the + next to the part called Drop_Off . Double click Composite Layups and create a 1 ply

composite layup as shown below.

Click Continue… and the Edit Composite Layup dialog box will appear. Double click Region under the

Plies tab and the dialog box will disappear. Now, click top ply partition that was created and it should

outline a red color signifying a proper selection, and click Done. The Edit Composite Layup dialog box

will reappear and the individual ply will show (Picked) under their respective Region.

Double click Material in the Edit Composite Layup dialog box and the Select Material dialog box will

appear. Since only one material has been created for this analysis, Graphite-Epoxy is preselected. Click

OK to assign this material the top ply.


9/16

Ply Drop-off 1

22.514 9 REV. D.S 4/28/12

Next, a relative thickness will be assigned to the ply. The problem statement defines a 0.150 mmthickness for each ply, but since conventional SI units are being used we will enter the thickness using

meters. (Note: the length and width of the laminate was sketched in meters, and the material properties

were entered in Pa, therefore consistent dimensional units of meters should be used throughout the

model) Double click Thickness in the Edit Composite Layup dialog box and the Thickness dialog box will

appear. Enter a value of 0.000150 in the Specify Value: option and click OK.

The final step in creating the composite layup is to assign fiber orientation to each of the plies. The

stacking sequence for this laminate is [0/90/0] therefore rotation angles of 0,90,0 will be defined in the

laminate. The rotation angle is calculated with respect to the 1-Reference axis. Enter0 in the Rotation

Angle boxes for plies 1. A datum coordinate system must be created for reference to the ply orientation.

Under Layup Orientation click Create… and the Create Datum CSYS dialog box will appear. Ensure


10/16

Ply Drop-off 1

22.514 10 REV. D.S 4/28/12

Rectangular is selected and click Continue… Click Create Datum. Click Cancel when the Create Datum

CSYS reappears. Next, click Select… and click Datum CSYS list… highlight Datum csys-1 and click OK.

Click OK in the Edit Composite Layup dialog box and notice how the top ply turned a turquoise color,

signifying a section has been assigned to it.

Repeat the same process to create a 1 ply composite layup for the middle partition (Note: make the

rotation angle 90 for this layup). Finally, create a 1 ply composite layup for the bottom partition (Note:

make the rotation angle 0 for this layup). A new Datum CSYS does not need to be created for the

different plies; the one created for the top ply can just be selected. If all the composite layups have been

created and assigned properly the complete model should be a turquoise color.


11/16

Ply Drop-off 1

22.514 11 REV. D.S 4/28/12

Generating a Mesh

Double click Mesh (Empty) in the model tree and the part will turn a pink color. Using the Seed Part

tool, create a global seed with an Approximate global size: of 0.000150. Click Mesh Part to generate

the mesh. (Note: If the analysis does not complete at the end of this tutorial due to exceeding the # of

nodes, increase the global size to a larger number, re-mesh the part, and rerun the analysis)


12/16

Ply Drop-off 1

22.514 12 REV. D.S 4/28/12

Creating an Instance

Expand the Assembly option in the model tree and double click Instances. Create an instance of the part

called Drop_Off by clicking OK.

Creating a Step

Double click Steps (1) in the model tree and create a General, Static, General Step. Accept all defaults

for this step.

Applying Boundary Conditions

Double click BCs in the model tree and create a Mechanical, Symmetry/Antisymmetry/Encastre

boundary condition on the left surfaces of the laminate. Hold Shift on the computer keyboard to select

multiple surfaces for this BC.

Click Done. Choose PINNED (U1 = U2 = U3 = 0) in the Edit Boundary Condition dialog box. Click OK.

Next, a y-constraint boundary condition will be applied to the model. Create another BC of Mechanical,

Symmetry/Antisymmetry/Encastre type on the bottom face of the laminate. Click Done.


13/16


14/16

Ply Drop-off 1

22.514 14 REV. D.S 4/28/12

Applying a Load

An axial load be applied to the model in the form of an x direction displacement. Double click BCs in the

model tree and create a Mechanical, Displacement/Rotation type boundary condition. Ensure that

Step-1 is selected in the Step: option in the Create Boundary Condition dialog box. Click the right edge

of the laminate and click Done. Check the box next to U1: and enter a value of -0.00001.

Click OK. Small orange arrows pointing in the negative x direction will appear on that surface.


15/16

Ply Drop-off 1

22.514 15 REV. D.S 4/28/12

Create and Run a Job

Double click Jobs in the model tree and create a Job called Dropoff. Accept all defaults and click OK.

Expand the Jobs (1) option in the model tree and right click the Dropoff job and click Submit. When the

analysis has completed, the Message Area at the bottom of the screen should look similar to the figure

shown below.

Viewing Results

Right click the job Dropoff (Completed) in the model tree and click Results. You will automatically be

entered into the Visualization module where the model has turned green and is oriented in an isometric

view.

Click the Plot Contours on Deformed Shape icon in the module and the Von Mises stress contour willappear.


16/16

Ply Drop-off 1

22.514 16 REV. D.S 4/28/12

The principal stress contour of S11 is to be viewed for the laminate. At the top of the screen change the

dropdown selection from Mises to S11. Both the contour and the stress values listed in the legend will

change.

Another way to determine the stress in an element is to query the element. At the top of the screen

click Tools -> Q uery… and click Element under General Queries. Next click any of the elements on the

model and the S11 value will appear in the Message Area at the bottom of the screen.

Conclusion

This concludes the FEA of Composites – Ply Drop-off 3D Example 1 Tutorial.

Composite Finite Element Project 3.PDF

Documents

Transcript of Composite Finite Element Project 3.PDF