Laminate modeling with Advanced shells?

[ygagnon]

Hi;

I am trying to model a simple rectangular plate (with three layers) using the advanced shell feature. What should the proe model be before I use the shell? (a solid or a surface?)... I tried the surface model but I am having "insufficiently constrained model errors" when I run it. This is a simple plate (load in the middle) and clamped at both ends.
Thanks for sharing your tips.
Y

 

[seymours2571]

Ygagnon,

You should use a surface. The laminate idealization pertains to shells.

Keep in mind that shells have 6 degrees of fredom. So if you are constraining 1 edge of your shell you will need to specify both translational and rotational constraints.

Good luck,

steve

 

[flyerfly]

You can use either a surface or a solid. If you use a solid then you have to pick the surface of the solid that you use as the shell. Either way you end up with just a surface for the FEA so you have to constrain it just like Steve said. The only time I use solids with laminates is if I intend to have mixed mesh models (solid and shell elements).

 

[cpinz]

Unless your plate is very thick, solids should be avoided.
Usually one uses solids if shear plays an important role and you need to know what happens in the core. But I believe this is not your case; besides the constraints will differ if you apply them on solids rather than on shells; then for a mixed structure you have to be aware of where you are applying them .

But why do you clamped both sides ? Do you really need to study an overconstraint structure ?

Cpinz

 

[mikechy]

flyerfly, some time ago you've mentioned, that you have assigned a moving coordinate system to follow the curvature of the part (in Nastran). Do you have such experience with Mechanica?
Thanks,
Mike

 

[flyerfly]

Yes I do this all the time.

Mechanica has the following options for material orientation on shells.

1. Referenced Coordinate system
2. First Parametric direction
3. Second Parametric direction
4. Projected vector

All surfaces have "direction curves" so you can assign the coordinates to follow these if you wish. I don't use projected vector much because if the surface has alot of curvature then you will have errors if the projected angle is to much. I use the parametric directions most of the time on curved surfaces.

You can find these options under "material orientation" in the shell properties.

If you are going to use laminates in Mechanica you need to have advanced mechanica, not just the regular one. Hope this helps.

Jon