Modeling a FRP shell with internal pressure in an assembly and FEA

[smith4464]

This a post I have on the Cosmos forum but I haven;t gotten any repsonse so I thought I'd try here -

I have an FRP ( fiberglass ) form that is being held by several external bracing "clamps". Basically the form is a W shape but with the the W vertices flat instead of pointed. The 'clamps" are aluminum extrusions along length-wise being rigidly held in place by bolts.There is an internal pressue of 30 psi pushing out of the form and the clamps are there to keep it from deforming to the point of failure, i.e. bubbling "too much" ( more than 1/2" inch ) or outright cracking.

Should I be modeling the FRP W as a shell? it is approx 3/16" thick. And if it is a shell what faces ( inside or out ) do I apply pressure?

I looked up some "numbers" for FRP to try and guesstimate material properties for it but am open to further input.

Thanks!!!!!!!!!!!!!!!!!!!!!!!

 

[rstupplebeen]

If you should use shells is a question about aspect ratio. If your part is only 1x1" then solids are appropriate 100x100 shells.

I am assuming that your pressure question is do you use the inside or outside face of the pressure vessel. Typically I have used a midplane however for large aspect ratio parts it really doesn't matter.

Fiberglass properties vary significantly depending on the layup, glass, resin, processing, fiber volume ratio, procity...

I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[kellnerp]

Best to post FEA questions on the Simulation/Cosmos forum.

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CSWP, BSSE

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[smith4464]

Thanks for the input, Rob. I wasn't sure about the shell guidelines. And, I'm well aware of the issues with material properties of FRP, was just wondering if others out there have the same issues and have come up with some ballpark numbers to use just to get and idea.

I know this is not the correct forum for FEA but no one replied on the Cosmos/Simulation forum.

 

[kellnerp]

I monitor the Simulation forum, but it is kind of dead these days. I think the SolidWorks forum is where the action is for FEA.

I made a comment that I don't see in this thread regarding FRP. Basically anything plastic or composite is so affected by process and choice of materials that it just doesn't make sense to do much of anything without some decent test data. And unlike metals, both humidity and temperature are huge factors which make a general rule pretty unsafe and difficult to do.

TOP
CSWP, BSSE

http://www.engtran.com

http://www.niswug.org

http://www.linkedin.com/in/engineeringtransport

"Node news is good news."

 

[smith4464]

Yeah, FRP material spec.'s are scary and a lot goes into affecting them but basic numbers to guess from can be helpful...

Another issue - when i run Comosworks ( 2008 ) on assemblies ( more than one component ) many times ( not always ) some of the components disappear during the analysis. I can drag pointer over them and the outline shows, but they and any graphical stress, deformation,etc. are missing.

Any thoughts?