AC3D does not have a UV unfolder. There are some 3rd party dedicated UV programs that support unwrapping/unfolding, with better results coming from more expensive packages. The ones of which I'm aware:
http://www.unwrap3d.com
http://www.polygonal-design.fr/e_unfold/index.php
The prices are vastly different on these two, but I really can't attest to the quality of the results from either. There also may be other mappers that I've missed, as it's been a while since I've needed this kind of texture mapping.
I'm not aware of any free plugins or packages for doing this...
There's also,
http://www.uvmapper.com/ , but I don't know whether it supports unwrapping.
Good luck