I've heard of the technique before. I have a CF seat post that has a clearly visible indentation in a small section where it has been clamped by a frame for a year. It rings the same as any other part of the post and there no thud whatsoever. Does this mean the damage isn't structural? BTW, I'm not currently using the seat post anymore.
The quick and dirty check for delamonation:
1. Find a coin/spanner/screwdriver with a nice ring when tapped.
2. Hold area of composite part to be tested horizontal (this wont be to hard with a wheel, but frames are more difficult).
3. From a hight of approx 10mm (It is more important to keep the hight consistant then finding an exact hight) drop coin/object on surface.
4. It should ring on the good and thud on the delamonated parts.
5. As a rough check tap about every 30-50mm and when you hear thuding close the tap spacing to mark out the exact area of delamination.
Boeing uses a more expensive version of this technique to test their wings and flaps (theirs involves water jets and ultrasonic taps in the water stream).