Material Optimization (fiber volume fraction)

Altair Forum User

Hi,

 

I already worked a lot with hyperworks but right now I'm looking for a possibility to optimize the material within a given volume. That means I have a component made out of undirected long fibers (material is idealized isotropic) with a fixed volume and want to know where do I need which fiber volume fraction. With lower fiber volume fraction, the density of the material gets lower (and the mass of course too) but the mechanical properties getting lower as well. And that's the optimization I want to have... high fiber volume fraction only where it is necessary to minimize the weight. I don't want to make a topology optimization because the shape and the volume is completely fixed.

So do you have any idea how i can handle this problem? I'm not sure if it is possible to have a continuous density distribution within the component with an optimization but maybe I can define for example 10 times the same material but with different fiber volume fractions (= different density, young modulus, yield strength...) and the program tells me where which material should be.

 

Thank you for your help!

Altair Forum User

Hi Marius89,

 

Can you try with Free-size/size optimization instead of topology optimization?

Altair Forum User

Altair Forum User said:

Hi Marius89,

 

Can you try with Free-size/size optimization instead of topology optimization?

Thank you for your answer.

Isn't Free Size Oomization only for composites? My material is card Mat1 and not a composite. And I think with this type of optimization I will change the outer shape of the component and that's what I don't want to have. Or am I wrong?

Rahul_P1

You can do free size on normal isotropic material models as well, you will get elements with varying thickness using free size optimization. 

 

The optimization can be to vary the size, shape, topology of a model but not the fiber volume fraction, i.e. it cannot tell you hoe much fiber must be in your material etc and also not where you must use which material,

 

In a way, when you do topology optimization, it gives you element densities, with which you can figure out where you must have high density and where you must have low density, this will actually serve your purpose, to

 

just run a topology optimization, then contour element densities in the results, you will then know where you must use high density material and where low density material. 

Altair Forum User

Hi i am running topology optimization,while running i am getting error message

 

*** WARNING # 1030
 Consistency requirement E=2G(1+NU) violated.
 Different values of G (either provided or inferred) will be used.
 See the Material Quality Checks section of the documentation.

 

This is the material card i have used

MAT1           2113800.044000.0 0.342   4.43-6  8.6-5

 

The same model run without any error in nastran solver.

Rahul Rajan_21763

Hi,

It is recommeneded in the documentation of optistruct to provide any two parameter is needed to define MAT1.It could be E & Nu or G & Nu or E & G ,then automatically optistruct will calculate the third parameter based on the above formula.

Regards

Rahul R