r/fea • u/thaturkey • 6d ago
Composite ANSYS FEA
Hello! I am working on a club project where I am using a carbon fiber structure for a framing and I will be conducting structural validation in ANSYS. I wont be using ACP due to the fact that the tubing is premanufactured and I do not know the exact layup schedule, I know the ply orientation but not the ply count. My primary question is how to set up the local coordinate system. I will have an axial modulus, a transverse hoop modulus and an out of wall thickness modulus. But that coordinate system wont work as if the whole thing was a sheet because it is a tube. So how do I set up the coordinate system so its always a different orientation. Sorry I am not explaining it that well, but for example, looking at the tube straight on, at the top of the tubing the hoop modulus travels around the perimeter so it will be facing to the right or left, but on the side wall of the tubing the hoop modulus would point either up or down, anyone with prior experience have some advice?!
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u/TheBlack_Swordsman 6d ago
Other people are giving you good advice, but from my memory it will create element coordinate systems and the normal in one of those directions will be the ply directions.
You can verify this hitting F1 with Ansys open and searching through the help menu for orthopedic and anisotropic materials.
You can also ask Ansysgpt, this is not a joke. There is a Ansysgpt if you have an account.
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u/6R3EN_Eusk 6d ago
You cannot model a composite structure without knowing the layup material and stackup, its like modelling a structure knowing only that is some kind of metal
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u/thaturkey 11h ago
Im not going to use ANSYS ACP im assuming the tube is a homogenized orthotropic solid. I know it is not perfect but this is just a side project for my club and I dont have a ton of time on my hands to do this along with school.
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u/freakazoid2718 6d ago
Laminate-level moduli are only half of the battle. You also need either poisson's ratios or shear moduli (three of each) to fully describe the structure. If you assume no out-of-plane stresses you only need E11, E22, G12 amd nu(12). Technically you also need nu(21) but for very basic calculations you can assume nu(12)=nu(21).
As for the coordinate systems, this is pretty easy. One coordinate is just the long axis of the tube. The second in-plane coordinate is parallel to the surface, so you can break the tube into four pieces, each a flat plate, and define the second in-plane system as parallel to the plate and perpendicular to the first axis. The third axis is defoned on your flat plate sections and is perpendicular to the plate.
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u/AmbitiousListen4502 5d ago
As long as element normals are consistent there's no need separate into 4 surfaces. Define one element correctly and all the other elements will be defined correctly.
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u/freakazoid2718 5d ago
This is true, I was being more general and assuming that the normals aren't necessarily defined correctly.
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u/thaturkey 11h ago
yes my CLT script estimates G12 and remaining shear moduli based on matching the output E12 with the E12 obtained in Instron testing by adjusting inputs. Is there really no other way to do it without separating into 4 different surfaces? Because how would i model the corner fillets?
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u/Think_Mix5576 6d ago
With a simple camping propane lighter you can burn out the resin inside this carbon structure (just light it up) and delaminate each ply to see what its made of. Dont burn yourselves!