Can’t find name of a product used in carbon fiber repairs
I found the video, and it turns out my memory was off. It’s a graphite powder mixed with epoxy. He doesn’t explain why he used graphite, but that layer of resin was only to prevent air leakage from inside the tubing during the vacuum stage, and probably also to help the carbon sheets lay flat. Perhaps the graphite was added to make the resin more sandable? In any case, it wasn’t a carbon mixture, and it does not provide strength to the repair.

I would be interested in hearing if anyone has knowledge of such a product.