# Solid shell elements

**URL:** <https://calculix.discourse.group/t/solid-shell-elements/1578>\
**Category:** Uncategorized\
**Created:** [April 6, 2023, 11:13am UTC](https://calculix.discourse.group/t/solid-shell-elements/1578 "2023-04-06T11:13:18Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![joao](https://avatars.discourse-cdn.com/v4/letter/j/7feea3/32.png) [@joao](https://calculix.discourse.group/u/joao)\
**Post date:** [April 6, 2023, 11:13am UTC](https://calculix.discourse.group/t/solid-shell-elements/1578/1 "2023-04-06T11:13:18Z")

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I see that elements of this type are not available in Calculix. Wanted to ask if there has ever been an effort to develop such elements for Calculix, perhaps as user element?

I’m primarily interested to use them for composite sandwich structures: in a thick shell formulation with good transverse shear modelling and a ‘natural’ representation of the thickness for the core material.

Another note: this question is on the traditional solid shell / continuum shell. But I saw that not too long ago, in Abaqus another solid element type (there named ‘continuum solid shell’: CSS8) was added. If I understand it well, that is essentially an incompatible mode, full integration solid element that is specifically made to work well for bad aspect ratios in thickness direction. It needs explicit indication of the thickness / stacking direction. That might also do fine for my application.

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**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\
**Post date:** [April 6, 2023, 11:53am UTC](https://calculix.discourse.group/t/solid-shell-elements/1578/2 "2023-04-06T11:53:06Z")

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Well, shell elements in CalculiX are kind of solid shells 😉 They don’t use actual shell formulation, they are just expanded to solid elements. There’s only one true shell element in CalculiX at the moment and it’s very limited.

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**Author:** ![joao](https://avatars.discourse-cdn.com/v4/letter/j/7feea3/32.png) [@joao](https://calculix.discourse.group/u/joao)\
**Post date:** [April 6, 2023, 2:14pm UTC](https://calculix.discourse.group/t/solid-shell-elements/1578/3 "2023-04-06T14:14:18Z")

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Aha! Thanks for your answer.  
Yes, I read that too in the theory manual. But somehow assumed that there would still be some difference in the calculation. The same C3D8R elements with tiny thickness vs. in-plane dimensions, in a single layer… that doesn’t intuitively seem like the best approach. But if they do, then all my troubles are solved 😃

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**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [May 3, 2023, 2:28pm UTC](https://calculix.discourse.group/t/solid-shell-elements/1578/4 "2023-05-03T14:28:38Z")

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This is lacking condition of linear shell element in CalculiX. Treatment has been done in coding with composite options, but only for quadratic type is currently available.

It’s good to implemented in the future of CalculiX to allow linear type to have composite feature also. Can give large benefit in computational times for plasticity and contact analysis without losing it’s accuracy.