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Optimizing with Rohacell core in optistruct

I'm trying to mass optimize a model with various loadcases acting on it... I want the result to have a rohacell core of constant thickness throughout the centre of the entire panel (to be left alone during the optimization) so I have two questions regarding this,

1)how can the core be left at say 5mm and not split up and shuffled in the stack during free sizing?

and 2) why do I get massive out of plane displacement when using the listed properties for a core material such as rohacell 71 and running an analysis?

Thanks for any and all help!

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Altair Forum User

Hi SSnell,

1) You can use CONST option in DSIZE to give a constant thickness constraint.

2) have a look at RANGE option in DSHUFFLE card. For your case you may require 2 RANGE bounds.

why do I get massive out of plane displacement when using the listed properties for a core material such as rohacell 71 and running an analysis?

Are the applied loads are inplane loads?

The out of plane displacement could be a result from coupling effect.

If you can share the model, I can investigate about the out of plane displacements.

SSnell

Thanks for the DSIZE-CONST advice,
The applied loads are out of plane and when analysing with the laminate set to Total it gives huge displacement perpendicular to the surface, Is there anywhere I can read/learn about this coupling effect to try and understand it? and maybe the best place to learn about analysing and optimizing models with a core in hypermesh?

thanks

Altair Forum User

Hi,

You can refer to any book which deals with laminate stiffness analysis. So the deformation depends on the way the laminate is stacked. For instance for a non-symmetric laminate, upon application of a tensile load there will be certain amount of bending in the structure.

But one of the assumptions for calculation of laminate stiffness is the stress are in-plane.