I bought a carbon fiber framed Trek Remedy enduro/all mountain bike and repaired a fist size hole/delamination in the downtube at home for about $50 in materials [1]. Five years later it's also fine.
And I've taken the bike off 6ft drops and ridden it decently hard most of it's restored life.
CF repair can be done and plenty strong, it's just more risky because the properties aren't isotropic and simple like steel/alu so you can't just weld in a piece of metal of roughly the same thickness. I would not want to repair a bike I don't ride myself.
I’d be careful welding aluminum. At the factory, post weld, the frames are then heat treated, and pulled back into shape (the heat treatment will distort them).
Welding after heat treatment will reduce the weld affected zone back to its basic untreated properties.
And I've taken the bike off 6ft drops and ridden it decently hard most of it's restored life.
CF repair can be done and plenty strong, it's just more risky because the properties aren't isotropic and simple like steel/alu so you can't just weld in a piece of metal of roughly the same thickness. I would not want to repair a bike I don't ride myself.
[1] https://medium.com/@fixingthings/fixing-a-trek-remedy-29-9-8... (yes, sorry it's medium)