Let's assume that social activist shut down metal mines in future. And we plan to built and launch another space station. Can we build it with carbon fibre? or is there any alternative to it? Alternatives do not include CNT and Graphene
A bare carbon fiber layup will degrade quickly, because the epoxy that holds the fibers together weakens with exposure to ultraviolet radiation, which is much greater outside the atmosphere than on Earth's surface. A good paint would help.
Also, the epoxy also weakens (softens) with exposure to the kind of heat that sustained solar exposure would cause. Also also, it becomes brittle with exposure to the cold of shadow. Again, good white paint, or "rotisserie" flying like the Apollo craft did, or, better yet, a metallic skin to both block radiation and dissipate thermal extremes.
Practically, epoxy composites would be trustworthy for internal structures at most. To "build" a space station out of carbon fiber might take so much metal that you might as well make the whole thing out of (recycled) metal in the first place.
A typical module on the ISS, Kibo,
is made from stainless steel, titanium, and aluminum.
carbon composite foam sandwiched between two carbon plates and coated with white ceramic paint