Zero composite thickness
Altair EmployeeHi All,
I'm currently attempting to run an analysis on a carbon fiber/honeycomb structure. The composites is set up off of a meshed 2D surface by creating plys to determine the direction, thickness, material, and selecting the designated elements. They were than organized by creating a symmetric laminate and than a PCOMPP property is assigned to the same 2D elements as the plys. When I put the 3D element representation on and turn on the composite layers, everything looks exactly how it should, but I am receiving the warning below warning when I run a check in Optistruct.
*** WARNING # 1569
for property id = 19.
Thickness is zero for this composite. This will produce meaningless stress
results and may cause singularity of the global stiffness matrix.
Property 19 is the property where it assigns the PCOMPP property. The analysis does run up until it hits error #153 which seems to be caused by the above warning.
*** ERROR # 153 ***
Exactly zero pivoting encountered during Numerical Factorization;
the model may have rigid body mode.
Solver error no. = -503
spc set id = 2
index = 1
Possible reasons are:
1) insufficiently constrained model,
2) having rigid body mechanisms within the model,
3) extremely ill-conditioned rigid element sets,
4) extremely thin shells (as used for 'skinning') that have MID2/MID3,
5) gap elements with extremely high stiffness (KA, especially KT or MU).
Check the model and rerun the problem.
(MECHCHECK may be used to find the rigid body modes. To do so,
change the input to be an eigenvalue analysis and add MECHCHECK.)
(WARNING: results obtained with MECHCHECK cannot be used because
the model is changed internally.)
This error was detected in subroutine bcsmtxfct.
Does anyone know what might be causing the initial warning in this model? It seems weird to me that it says that it has zero thickness but when it's in 3D element representation it shows the thickness of the carbon layers and the honeycomb core.
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Hi Prakash,
Thanks for the response. I double checked all of the plies and all of them have a thickness and have the PLY card image. Any other ideas of what it could be?
If it helps, I have set up the carbon fiber/honeycomb structure using the steps in 'Composite Optimization with OptiStruct 11.0 on the example of a Formula-Student-Monocoque' tutorial off the Altair website. The hypermesh version that I am using is v12.0.
Hi ZDecker3
Please check if any plies in the laminate has zero thickness or missing a ply card image.