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What exactly will UV do?
It won't do much at all to the carbon fibres, but it can degrade the resin matrix.
I'm more worried about small chips and knocks breaking fibres and leading to much bigger problems
The principle benefit of fibre reinforced composites compared with homogeneous materials is that small chips don't lead to bigger problems (more precisely, the composite structure has mechanisms to resist crack propagation which don't exist in crystalline materials)
Water doesn't damage carbon .. It's UV or when you break the fibers that a setup for failure is introduced.
You need to use a UV resistant clear coat .. or use a specific carbon polish / wax which has a UV protection additive