solid-mesh contact Femap-Nastran

[jlrp]

hello all,
I am trying to calculate a foil which consists of a laminated carbon fibre skin on a foam core.
I have meshed the skin with 2D shell elements and the core with 3D solid elements
I have tediously made all the contact regions and connectors using a glued property
the static analysis doesn't work "excessive pivot ratios" and when I force it with PARAM,BAILOUT,-1, the total translation contour shows local peaks which shouldn't be there
When I run a similar model without the foam core and just the skins it works fine so I'm guessing the problem is in my connection between the shell and solid elements.

any hints on something that is often done wrong in this case ?

note: I have built the geometry in rhino, the foam core is a closed polysurface and the skins are open surfaces of the exact same shape as the core. the foil will be built on a female mould so I have offset the laminate properties so that they extend towards the inside of the foil, that means when you turn thickness on, they overlap on the 3d solid elements. Is it a source of error ?

thanks in advance

 

[Naffoussi]

Hi,

You can use mesh / Edge Members command to create a skin (plate elements) for the core you meshed using 3D elements.
Then define the correct property for the skin.

No need for glued contact for this study.

For the elements overlap you can define an offset for the skin elements.

Regards,

Seifeddine Naffoussi, Stress Engineer

 

[jlrp]

thanks, I´ll try that, but the problem is that my skins have complicated degressive layups so the surfaces are broken down in a multitude of small surfaces, to which I assigned all the different attributes before meshing.

 

[jlrp]

Hi all
I have made some progress on glued contacts, my models run correctly now and I have a question regarding post processing: Femap with Nastran proposes results 253 to 265, glue traction, glue force, glue moment.
Can somone explain to me what they represent, and what units are used ?
do they mean the same thing for surface/surface and edge/surface contacts ?
I have searched the nastran guide + google without any luck for the moment...