They're very tough. I've never seen one snap or crack like a plastic blade.
Most of the time, you'll see small chips on the tips or leading edges of the CF blades-depending what you hit. But it does take a pretty hard thump against a pretty hard object, even to get them to do that.
Just remember, they're hard...and if you're flying in the house, CF blades will do alot more damage to whatever you come in contact with. The weak point with any blades is where they bolt on. The pivot point and hole doesn't usually have much material around it. I have some Hornet CF blades on my hummingbird. They're awesome blades, but they'll break readily right where they bolt on. Hopefully, in your case the Pic CF blades have more material there. Might be something worth looking into. Also, in SOME cases you may need to re-gear slightly to handle the CF blades. The undercamber in them doesn't give like plastic. Sometimes a motor needs more grunt to swing them like it did with the plastic blades. Most of the time going down one tooth on the pinion is enough to do it. Whew...man is this response getting windy..anyway..good luck !