Alright. So for context, I’m trying to model a robotic arm that has a section that opens up like a flip phone. I’m doing this on a shapekey.
I can’t figure out how to “straighten” the part that contains the “screen” when it’s open. It’s fine closed, since I want it to follow the shape of the arm.
It looks like your mesh already has thickness built in.
This would be much easier, if you had only a planar mesh (even if curved) and used a Solidify modifier to get the desired thickness.
If you have a curved zero-thickness mesh (like pictured above without the thickness),
then to setup the shape-key:
put the 3d-cursor at some vertex in the mesh,
change the Transform_Pivot_Point to “3D Cursor”,
then Scale the mesh along one of the coordinate axes
(for instance, with hotkeys: S Z 0 (zero))
then store this planar result as the shape-key.
I hope i’ve understood your situation correctly.
Good luck.
You might ty to delete the inner part except the border and using the Loop Tools addon Gstretch feature on all for border sides like so (maybe don’t delete the next inner part and align between this two loops to your liking):