Composite Optimization: constrain core thickness just in one specific region

Rahul_P1

Hello,

i want to do a composite optimization and constrain in one region or on some elements the total laminate thickness or the thickness of the core ply because of not enough space in that region.
The whole laminate can have a total thickness of for example 25mm except these few elements, which should have a total thickness of 10mm.
I use shell elements and as objective minimize weighted compliance. The mass is constrained. I am in the Freesize Optimization Step.

How can i do that?
Of course i could constrain the total laminate thickness to 10mm everywhere, but i think this would not be the lightest solution.

Another question: Actually i want to minimize the weight by simultaneously complying a specific stiffness for a loadcase. So OptiStruct should decrease the mass, if the displacement/failure mode constraint is still fullfilled. Why is it done the other way round in every tutorial? What are the disadvantages doing it with minimize mass as objective?

Thank you very much for your help.

Rahul_P1

Henrik,

Have you tried - creating another property with the same ply structure etc > apply to just the few elements which require a different laminate thickness constraint > then create another design variable with this property > this design variable give the different laminate thickness constraint. ?

See OS-4090: Manufacturing Constraints in a Free-size Optimization of a Composite Structure

where mass is reduced for a given displacement constraint, to be precise -

Objective:
Minimize the Mass.
Constraints:
Displacement of selected 6 nodes < 3 mm.
Design variables:
Thickness of each ply of each element in the design space.