modeling of an isogrid composite structure

[cspkumar]

We are building a rigid elliptical torus with helically wound pre-preg carbon fibers at -/+ 30 degrees. There are 15 windings each in the clockwise and counter clockwise direction.

Since its difficult to model the helical windings, I was wondering if there is a way to model it with shell elements and use the orthotropic material properties to represent the helical windings.

Could anyone please help me on how to obtain the representative material properties which I can use for an equivalent shell model?

Thank You,
Kumar

 

[jhardy1]

Kumar,

Does your FEA package have a laminar composite capability built in? Many do, but it may be an optional module at additional cost.

If you have a laminar composites capability, it should be fairly straightforward. Build a shell model, and then generate the laminar composite shell properties. The packages I am familiar with typically use a 2-step process:

a) Define each of your laminae, which is typically done by specifying orthotropic material properties for each layer, including the angle of lay-up etc;

b) Define your laminar composite shell element property, by defining the order of laminae in the construction.

This will then generate the appropriate element stiffness matrices, and will also enable you to recover the stress and strain resultants (including failure criteria etc) when you go into post-processing mode.

Hope this helps!

 

[cspkumar]

Hello,

Sorry if my question was not clear. The problem what I have is how to obtain the orthotropic material properties of helical windings so that I can model them as shell elements instead of windings?

Thanks

 

[rajsen]

Hello,
I think you can model your helical windings as laminar composite shell elements, as Julian suggested. In Ansys the elements like Shell99 and Solid46 can be used for this purpose.
Actually I am a new Ansys user and started off with it only recently. I am a bit confused in the following matter-
Suppose you take an element, say Shell99, specify the orthotropic material properties and the thickness and orientation of each layer. Now when you mesh a shell, say a conical shell, with the above element, what will the specified orientation actually manifest itself as on the cone? Will the fibres in a particular layer be continuous from element to element as desired?
Thanks
Raj

 

[racecareng]

I would recommend to model the helical windings like a fabric with a fibre orientation of 30 degrees.