My parents are visiting over the Labor Day Weekend, and I showed my dad the carbon fiber soles of my Shimano SH-R215 shoes before I went out on a morning ride. He mentioned they must be pretty light, and I said they were stiff too. My dad’s a rocket scientist (he works for Thiokol which makes the solid rocket boosters for the space shuttle), and he mentioned that they use carbon phenolic as an ablative material for rocket nozzles since the 5,000 degree heat of the rocket’s exhaust will only create a burnt carbon layer on the surface of the nozzles instead of quickly burning through if the nozzle was made entirely out of metal. I’m not sure how carbon fiber would stand up against 5,000 degree temperatures.