What applications/load directions etc? Almost any epoxy will bond to a keyed metal surface, just not with the sort of strength you’d want in a safety critical application unless you’re a qualified composites engineer (we do have one on here IIRC). Incidentally epoxy is pretty much the sole matrix material for carbon fibre bike parts and in that case it’s usually bonded to things like the alloy forms for the headset, BB, dropouts etc. The joints need to be thought out carefully though, as “peel” is a weak point, my old crank arms delam’d from their alloy square taper bits due to the rotational forces peeling the bonding away from the alloy surface.
