While this did not happen to my I-20, I have witnessed carbon fiber masts and their interaction with lightning. Had a windsurfing mast rigged as an extension of a CB antennae in the Bahamas and it was hit by a bolt one afternoon. Yes, the antennae and cable did act as a lightning rod, but the middle part of the carbon fiber mast exploded into a large number of splinters. I would guess that this same effect would occur on a larger and thicker CF mast (windsurfing masts are only about 12-15' high). It would probably be due to the extreme heating experienced during the lightning strike.
In the CF mast on a cat, if you were sailing in a storm, I would figure that the film of water on the mast would act more as the conductor than the mast itself. Due to the heat of the lightning, I would suspect some major heat damage in the form of splintering/fractures.
If I recall correctly, they conducted tests on helicopter rotor blades and airplane wings to determine what would happen in the event of a lightning strike (**safety tip**, chopper blades create a bunch of static electricity while hovering, so never grab a rescue cable from a chopper until it hits the ground first!). The aluminum skinned wings/blades emerged relatively unscathed, while the carbon/composite types suffered severe damage. There are even some USAF freaks who PURPOSELY fly jets through lightning. You should see the video!
