Pre-Analysis & Start-Up — Lesson 2

Pre-Analysis

The analytical calculation of the problem is 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.

Start-Up

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

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

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

Setup the Material Properties

The material properties for composite materials are different from typical isotropic materials, because some material properties depend on direction. Also, monocoques 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 clicking 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 as shown below:

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, 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:

5250 Core

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

Steel for the Suspension Links

Suspension links are normal isotropic materials. They are purposely 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: