I know that you need a special nozzle to extrude abrasive filament (carbon fibre, copper, ...). I do have such a nozzle (coated steel) and am printing carbon fibre and copper filament. Last time I used it to print carbon fibre PLA. It worked well, however when I removed the nozzle from the hotend I realized that I could no longer screw the non-abrasive nozzle in (the dirt cheap 0.1$ china nozzles that work well enough for most materials) and the thread of the hotend was completely loosened up.
I had been working on a few other things with my printer, so I am not entirely sure what caused the thread to become loose, but I was wondering, are there some requirements to the hotend excluding the nozzle when printing abrasive filament?