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Pre-Analysis

The analytical calculation of the problem are explained in this PDF document.  These passages are taken from the isotropic analysis section of "Design, Analysis and Testing of a Formula SAE Carbon Fiber Monocoque Chassis" by Jingsi Wu, Owusu A. Agyeman Badu, and Yongcheng Tai.  

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Start-Up

Open ANSYS Workbench

Open ANSYS Workbench by going to Start > All Programs > ANSYS 14.0 > Workbench 14.0. This will open the start up screen as seen below:

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Expand Component Systems, then drag ACP (Pre) to the Project Schematic window, as shown below.

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Save the project and name it, Name the project: Modal Analysis of a Composite Monocoque.

Import Geometry

Set-up the Material Properties

The material properties for composite materials are different than typical isotropic materials, because some material properties depend on direction. Also, monocoque typically have a sandwich structure consisting of carbon fiber layups surrounding an aluminum core. The following steps show how to enter orthotropic properties into ANSYS.

T300 Weave

Double click  Engineering Data 

Add a new material by click into the text box, and name the material "T300 weave".

To enter an orthotropic material property, go to  Linear Elastic  > (Drag) Orthotropic Elasticity onto the new material. A lists of property information will appear in the Property Outline To Import Geometry, go to File->Import... A dialog box will open as shown below:

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To view the .igs files, go to the pull down menu to the left of the File name text box and change it to Geometry File(...). Go to the location where you saved the monocoque.igs and click Open. Your workbench should look this:

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Build the Geometry

This particular geometry have contains solids, surfaces and line bodies. In default setting, Ansys do not build the line bodies, but we can change that with following steps:

Double click Geomtry  to bring up the Design Modeler

Select  inch  as the unit and hit  OK 

Under Detail View Penal, change Line Bodies to  Yes  as shown below:

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Now CLick  Generate  to build the geometry.

This will make sure line bodies will be built along with the surface and solids.

Here are the corresponding properties for this material:

Ex = 8.5E6 psi
Ey = 8.5E6 psi
Ez = 1E6 psi
Vxy = 0.06
Vyz = 0.06
Vxz = 0.06
Gxy = 5.6E5 psi
Gyz = 5.6E5 psi
Gxz = 8.3E5 psi

This type of composite is weaved, so you have to define that as well, go to  Physical Properties  > (Drag) Density and Ply Type on to the new material. Enter 0.056 lb/in^3 for the density. Also, expand ply type and select  Woven  from the pull down menu.

Next step, we need to define the stress limits and Tsai-Wu constants for failure analysis. Expand  Strength > (Drag) Orthotropic Stress Limits and Tsai-Wu Constants on to the new material.  Enter the property values that are shown below:

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5250 Core

Enter the properties for the 5250 Core as was done for the the weave. The values are displayed in the figure below:

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Steel for the Suspension Links

Suspension links are normal isotropic materials. It has purposely been made to be really stiff, so that the deformation of the monocoque can be seen more clearly. Here are the properties to use for structural steel:

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Go to Step 2: Go to Step 2 - Geometry

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