Mmmm ....
Nooby .....
An opportunity I had to (personally) visually inspect 2 areas of de-bonding on the 139 airframe both of which had the surface skin removed to reveal the "honeycomb" below ... showed a material which was not aluminium honeycomb but which appeared to some sort of "Kevlar" type honeycomb product (or similar) if I am not mistaken (and it has been known for that to happen, on more than one occasion) I would respectfully suggest that this construction is then truly a "composite construction" by definition ie one composed of dissimilar materials! Those areas were ... The Top deck area between the engines normally occupied by the exhaust ducts , and the area of de-bonding on the RHS of the tail-boom exactly where this "incident" damage occurred.
I must acknowledge however to not having been privy to an Engineers course on this Airframe (just a "drivers' conversion!) much to my personal frustration! .... as usual I stand to be corrected as necessary!
Cheers