They would be plenty strong enough as long as you use the correct resin. The problem, however, comes as to the breaking point of carbon fiber. Unlike metal/alloys which when put in contact with the curb just chip or leave marks on the wheel, the carbon fiber wheel would be prone to a complete break. Carbon fiber does not give like metal does. Same reason you can't use carbon fiber inside an engine, eventhough it would be really cool. Imagine a self-lubricating engine that is super lightweight.