From Ducati.org.--------
Carbon Fiber Wheels
I can agree with Tye for once —forged aluminum would be my choice. Magnesium is lighter but it's highly reactive when you have a chip in the paint and it's exposed to moisture in the air.
I have over 20 years of analytical and practical experience in failure analysis of high-speed rotating machinery, so here’s my opinion on carbon fiber wheels, for what’s it’s worth.
Simply stated, carbon fiber composite material is not a suitable material for wheels because they can—and do—fail catastrophically. For this reason alone they are not as safe (today) as a metal wheel.
There is no question in my mind that today’s carbon fiber wheels are stronger than their alloy wheel counterparts. Their main drawback is that they can be damaged internally in a number of ways, so just a visual inspection is insufficient to assure their continued safety.
At its strength limit, carbon fiber reinforced resin cracks—which causes it to loose structural integrity, whereas metal stretches and then breaks after the amount of stretch becomes too great.
It’s obvious that a dented, cracked or bent metal wheel has been damaged, and it’s easily determined using X-ray and liquid penetrant inspection whenever you have fabrication problems such as casting voids or internal cracks caused by fatigue failure or crash damage.
I would be mainly concerned about damage that can occur after the carbon fiber wheel leaves the factory, and I’m particularly worried about undetected damage caused by conventional tire mounting equipment and untrained operators. To my knowledge, they’re currently all untrained operators since the wheel manufacturers have not provided any specific guidelines on how — and how not — to mount tires on their wheels.
Further, damage from road hazards will not always be to visible surfaces and (again, to my knowledge) the manufacturers provide no useful inspection methods or acceptance criteria to the owner.
What’s a good criteria for determining significant damage to carbon fiber? We don’t really know yet. For example, Boeing designs and builds a lot of carbon fiber structures defines Barely Visible Damage as impact damage that results in a 0.10 inch long defect that is visible from three feet away. Boeing says that the impact that causes Barely Visible Damage is sufficient to affect the structural integrity of the underlying CF structure.
That said, if I hit a large object or pothole in the road I’d be very concerned about continuing to ride on a carbon fiber wheel. I’d certainly avoid buying a second-hand carbon fiber wheel or any wheel involved in a crash.
I'm not alone in my opinion. Asked recently whether Ferrari would use carbon fiber for structural elements of their production cars, Ferrari chief executive Amedeo Felisa said that its implementation will, for the time being at least, remain limited to the Enzo stratosphere and not used in its production models. According to Felisa,
"Nobody today has a real understanding of what happens if you damage a carbon fiber structure."
Given its decades of experience with the material in F1 and the hundreds of on-track crashes that it surely accumulated over the years, if Ferrari doesn't understand it, we struggle to imagine who does.
Ref: Damage and Failure of Composite Materials, Talreja & Singh, Cambridge Press