It's true theoretically carbon fiber filling will always reduce Impact resistence, but it shouldn't be too much of an issue for this application when the polymer already have exceptional impact resistence and thus a lot of headroom to spare. In other words, because of how the polymers like PA/PC already have so much impact resistence, the stuff usually riot shield or motorcycle helmet shell is made of, there will still be more than enough impact resistence after the impact resistance reduction from CF filling, to be sufficiently impact resistent for a throwing mug LMAO