The "TAP" test has been used to detect de lamination on composite materials for years. I ,personally have used it on things as widely differing as Wessex tail rotor blades and 757 spoilers.
The test consist of LIGHTLY tapping the area to be inspected with a coin. The Tapping sound you get will change sharply when you reach an area of delamination. (The sound you get is obviously impossible to discribe, but it's a "dull" sound!).The problem is that the sound produced will change slightly when you pass over an area of re inforcement, differing thicknesses and near the edge of the componant. Experience will tell you the difference but I would recomend any one who hasn't done it before to get a LAME to "walk you through it".
The test is good but should not be relied on 100% as the sound change will lessen the deeper the dis-bond is within the material. Pleae refer to the relevent MM for the tests for that!
I hope that might be of some use to you
Rgds Dr.I.