# Problem with orthotropic material and orientation in Solid Section

**URL:** <https://prepomax.discourse.group/t/problem-with-orthotropic-material-and-orientation-in-solid-section/2946>\
**Category:** General Questions\
**Created:** [September 3, 2025, 12:46pm UTC](https://prepomax.discourse.group/t/problem-with-orthotropic-material-and-orientation-in-solid-section/2946 "2025-09-03T12:46:08Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Tetelle08090](https://avatars.discourse-cdn.com/v4/letter/t/7ea924/32.png) [@Tetelle08090](https://prepomax.discourse.group/u/Tetelle08090)\
**Post date:** [September 3, 2025, 12:46pm UTC](https://prepomax.discourse.group/t/problem-with-orthotropic-material-and-orientation-in-solid-section/2946/1 "2025-09-03T12:46:08Z")

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Hello everyone,

I am trying to run a simulation in PrePoMax with an orthotropic material (defined with _Elastic, Type=Engineering Constants_). My model is a solid mesh (C3D10 elements).

The problem is:

- When I assign the material to my part, I don’t see any option to assign an Orientation in the Solid Section dialog.

- In the exported `.inp` file, I only get:  
\*Solid Section, Elset=Solid\_part-1, Material=Material-1  
but I would expect something like:  
\*Solid Section, Elset=Solid\_part-1, Material=Material-1, Orientation=CS\_fibres\_x

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<div class="post-metadata">

**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [September 3, 2025, 12:53pm UTC](https://prepomax.discourse.group/t/problem-with-orthotropic-material-and-orientation-in-solid-section/2946/2 "2025-09-03T12:53:24Z")

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> [@Tetelle08090](#):
>
> Is this feature available in the GUI, or do I have to manually edit the .inp file?

That’s exactly the issue. Orthotropic materials aren’t supported in PrePoMax yet and thus orientations are also unavailable. However, you can use the Keyword Editor to define them. The simplest syntax (assuming rectangular CSYS) is:

> \*ORIENTATION, NAME=…  
> a\_x, a\_y, a\_z, b\_x, b\_y, b\_z

So you have to specify the XYZ coordinates of two points: **a** (lying on the local X axis) and **b** (lying on the local XY plane but not on the X axis).

 ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/9/9e082563be98acc269a586e2ed92af952546e5ce.png)

You can find several examples on the forum.

You will also need a custom \*SOLID SECTION keyword to include the ORIENTATION parameter.