That's usually referred to as carbon "tow".

Chopping up fibers and mixing them with resin is not a very good way to acquire a lightweight repair. The mixture will become unusably thick and blotchy long before you get an efficient resin to fiber ratio (I've used fiberglass in a similar fashion it in the past to make large thick parts - it works well as long as light-weight isn't important). You are better off using a fine woven or mat cloth with resin to perform a repair like that.