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Optistruct - composite free size optimization

kc97eiy9_21097

Hi,
I'm working on composite free size optimization and I have a question.
What is the influence of initail ply thickness on optimization results?

For example, I have compliance minimize objective, static displacement response and constraint and 4 super plies (45, -45, 0, 90) with initail thickness value 0.2mm. In this situation solver can't get feasible design because displacement constraint is vaiolaited.
On the other side when I change initial ply thickness value to 1mm. I get feasible design and good looking ply shapes.
So how initial ply thickness can affect the results that much?
If i had good understanding of free size optimization, solver should get optimal super plies thickness and shapes to meet constraint but in my case it depends on initial ply thickness.

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Altair Forum User

HI,

I think if you are not providing any laminate thickness bounds, solver uses native thickness to optimize and that is what happened in your case.

0.8mm thickness may not be sufficient to constrain the laminate to a certain displacement and converge to the objective.

kc97eiy9_21097

Thanks for your reply.
I had defined laminate thickness from the beginning:
min laminate thickness: 0.2mm
max laminate thickness: 30mm
but it has no effect on the results.
My target for the static displacement for one node is 0.22 mm but on convergence plot displacement stabilize after third iteration.

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Altair Forum User

@holmesthinking Does the run stops after 3 iterations?

If yes, can you share the .out file, please?

If not, let us wait for some more iterations to com out.

kc97eiy9_21097

Optimization stops after 11 iterations but after 3 displacement and compliance stabilize.

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Altair Forum User

@holmesthinking

Can you share the .fem and.out files, please?

Simon Križnik

Hi,

So how initial ply thickness can affect the results that much?

Different initial design starting points (ply thickness or initial material fraction) could potentially result in different optimum solutions.

Please refer to the attached document from Optistruct User guide. I would also recommend the free eBook: Practical Aspects of Structural Optimization (A Study Guide)

Unable to find an attachment - read this blog

Altair Forum User

Hi,

Different initial design starting points (ply thickness or initial material fraction) could potentially result in different optimum solutions.

Please refer to the attached document from Optistruct User guide. I would also recommend the free eBook: Practical Aspects of Structural Optimization (A Study Guide)

could be... and this is my last option.

I would try with some manufacturing constraints and check if that helps before proceeding to GSO.

Unable to find an attachment - read this blog