[RRLedford]

The carbon fiber weight advantage comes with liabilities, as far as its greater difficulties for mechanically attaching it to other structural components without damaging the carbon, or concentrating too much stress in one spot.

I would only consider it for long swinging arm type use where faster speed movement with less torque loading is desired. For use as an axle, especially a power transmitting axle, I would veto that idea.

Is it because the axles are bending, or what other problem are you concerned about with the steel? Weight only? If it's weight, can you just go slightly larger with axle OD and use 7075 or 7068 aluminum?

BTW, you often will need to have some good gluing skills and high performance adhesives available for making any durable & reliable carbon fiber joint assemblies on your robot.

-Dick Ledford