Yes, by moving the question to tubulars you are totally reframing the question..
Tubulars exist for low weight... so most carbon tubular rims are more or less equal in fracture energy to each other (disregarding flaws, prior damage, etc..) and have fracture energy on the order of 1.5-2x that of a light aluminum tubular. The difference of course is that most are willing to consider a dented tubular as 'OK' and a cracked carbon tubular 'not OK' when in reality both of them should technically be considered past their useful life
I always thought about this from the perspective of 'what if this were a frame'... people who crash their carbon frames and break them never think, 'if only it were an aluminum frame and it were only dented and misaligned so I could just bang on it with a mallet and make it "fine"' However, this is how people think about carbon rims all the time.
The challenge for manufacturers in the tubular category is that people are buying based almost exclusively on weight so it's a really tight corner that they have to navigate to be light enough to be purchased and then strong enough to withstand some pretty severe hits at really low pressures.
Similarly, I leave in a few days for the Flanders-Roubaix week and we've had a similar struggle with teams over the years.. the aluminum rims would finish the week with dozens of small dents and the teams always want to keep using them.. while the carbon rims finish with dozens of little micro fractures and such and the team wants them replaced immediately. From the riders perspective they don't want to see either one again and if everybody is doing the right thing, they will be on all new stuff next year!
J
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