Unless it is a cylindrical or conical surface, you need to have the sheet metal module. I don't know it as fact, but I have recently read that you can use it to flatten sheets with "woven" characteristics, so more deformation is now allowed. Hopefully someone more familiar with that module will comment.
I use the Composite Flat Pattern Tool in NX1 and NX2. This can flat pattern with two options, Unidirectional or Woven material.
I think it may be used for other applications than composites with caution.
You need a special License to run that tool.
It was called Composite pipeline in NX1 but changed name in NX2. The tool is to my knowlegde the only remaining of "the UG composite module"
agree with erland
but in my opinion, except for cylinder, cone, or ruled surfaces(linear), other double curvature surfaces can not be flattened properly. it will be approximated and must be experienced in shop.