I was asked to look at what might be delamination in the down tube area during an inspection procedure. At first we could not solve where a creaking sound was coming from because the scanner could not find anything and it sounded similar to de-lamination so we had to find it.
I won’t mention the brand but when we inserted the endoscope we came across some expanding foam in the middle of the downtube cavity which impeded our exploration further. I asked for the downtube to be squeezed while we had the endoscope in position. We discovered that the expansion foam had slightly come away from the carbon wall causing the part to creak when he road it.
It seems some manufacturers have found a temporary solution to rattling internal cables. I say temporary because mid downtube sections are susceptible to flexing during riding which in turn can cause this rather minor de-bond over time. As small as this is it simply drives the rider nuts with irritation and concern. Hope this helps someone!