Learning Forum

[MargretSR]

Hello

Is it possible to do a FEM analysis on an assembly of two composite plates bolted together with two metal bolts? I have the assembly saved as a solid model generated from Solidworks, is it possible to assign a metal material to the bolts and a composite layup for the two different plates and simulate this all together?

Best Regards, Margret

[peteroznewman]

Yes Margret, it is possible. You would use frictional contact between the two composite faces touching, and between the bolt head and one composite outer face and between the nut and the other composite outer face.  You would put a Bolt Pretension load on the shaft of the bolt.

What answers do you want from the model?

[MargretSR]

I would like to load the model with a force and see where it fails, how much load the composite material and bolts withstand. Should I load the assembly as one assembled geometry file and use ACP pre to model the composite plates or should I load each part individually and combine them into a static structural? Thanks!

[peteroznewman]

You should build the model using all parts assembled and use a two-step solution in Static Structural. Step 1 is to apply the bolt pretension, step 2 is to apply the load to the assembly. Both steps will need many substeps to gradually apply the loads. The steps are assigned the units of time, so step 1 goes from 0 to 1 second while step 2 goes from 1 to 2 seconds. It's not real time, it's just a way to keep track of how much load has been applied. To determine the failure load, you need to plot a quantity that has a failure threshold. Plot that and look up the time at which the threshold was reached. If the time is 1.8 for example, then the failure occurred at 80% of the applied load. 

Yes, you use ACP Pre to model the composite plates. However, since you are new to ANSYS and FEM analysis, I recommend you do this twice. First build it with an isotropic material like Aluminum, and gain the skill to build the model and get the result. Then build a second composite model using ACP Pre/Post. I can help you with the first model. Are the parts already designed in a CAD system? Please reply and insert a screen snapshot image, or make a pencil sketch and insert an image of that if there is no CAD. Highlight where one part is fixed and where the other part has the force applied.

[MargretSR]

I have the design in a CAD system but here is a simplified sketch of the assembly, the plates are composite layups and the bolts are metal. 

[peteroznewman]

Hi Margret, thanks for the sketch.

When you show a fixed support underneath, that would physically represent an adhesive bond to some sort of rigid block. That would end up being the weakest point in the assembly because the composite layup would delaminate at that end first. Do you agree? You don't need to model the bolts or the other part in that case.

If you want to see the failure around the bolt heads, then make the bottom piece 4 times wider than the top piece, or at least 2 times wider and also fix an area on the top face of the fixed piece, as well as the underneath face.

When modeling the bolt and nut, you can have a single dumbell shaped solid that has two heads, you don't need a separate part for the nut. The head faces should be touching the faces they need to compress.

[MargretSR]

Thank you for all the help! My model does not look exactly like the sketch but it has the basic setup of my model. But I have now been able to successfully model this with just isotropic material and want to try defining the plates as composites. I do not see exactly how the Workbench setup should look. Where do I connect the ACP pre/post? This is how my setup is now:

[peteroznewman]

Hi Margret,

I typed ANSYS ACP TUTORIAL into YouTube search.  There are several videos. Here is one.

https://youtu.be/PQItLgfTxnE

 

Link to related discussion.

 

[user deleted]

Hi peteroznewman, could you please tell what kind of issues can occur if I model bolts as a beam elements? My model doesn¨t converge seems like because of the bolts. I have Composite+Metal connected with bolts.

Thank you in advance

Kamilla

[tumulpurwar]

perfect post,Could not find how to bookmark, so commenting here, Thanks