Each time I’ve tightened them up a bit more, but I can see the carbon splintering now.
I’m trying to salvage what I’ve got, rather than buy some new bars, even if it means trimming 15mm off each end of the bars to get rid of the damaged parts.
Be very cautious. Even with some damage carbon fibre can retain a lot of strength but teeth are more expensive than bike parts.
The specialised ones will be designed for their bars, not all will have the same internal diameter so it would be worth checking this. You con’t want to force them into an inner diameter that is too small and they might not expand evenly in an inner diameter that is too big giving high stress at crush points.
Also be VERY careful when fitting any kind of expanding plug into a carbon tube. You are more likely to de-laminate the outer layers when expanding the tube. It is basically like you are turning it into a pressure vessel and composite pressure tanks are very strong but designed for it. Your bars are designed for bending stiffness and strength along the bar and an expansion force is just going to break apart the resin bonds between the fibres.
They will probably come with instructions anyway but I would say to only start to expand when the bar end is in place.