When WILL people stop trotting out this old chestnut that you can X-Ray a carbon frame to see damage?
Firstly, who do you think would allow you to use their valuable X-Ray machine to examine a poxy bike frame? X-Rays are used for examining things like bones hidden inside humans and cargo hidden inside seafreight containers.
Secondly, a carbon bike frame is made from a resin plastic reinforced by a mesh of carbon fibres, which give it massive structural strength but very low resistance to point impacts so a thin-walled "carbon" tube is easily punctured. If you stress a carbon frame enough to overcome its considerable strength it will snap catastrophically and there will be no doubt. If you manage to stress it in such a way that you break the resin without breaking the reinforcing carbon it will certainly crush and become flexible like a green stick. A point impact from, say, a pedal or bar end will overcome the strength of the plastic and punch through the wall as many have found. In the same way a reinforced concrete beam is massively strong in tension and will support a wall but whack it with a hammer and the concrete casing will fracture exposing the reinforcing rods and allowing the beam to sag. So if you succeed in breaking a carbon frame, simple examination will quickly reveal the break if the frame is still in one piece.
