Definition
A separation between two bonded surfaces in a composite or adhesively joined structure, where the bond between layers or components has failed but the materials themselves remain intact.
Plain English
A spot where two glued or bonded layers have come apart, even though each layer is still in one piece.
Context Anchor
Seen in aircraft maintenance, especially with composite parts, bonded panels, fairings, and adhesive repairs.
Derivation
From 'dis-' (apart, undo) + 'bond' (a joining or sticking together). Literally 'an undoing of the bond.' The word makes clear that the failure is in the joint itself, not in the parts being joined.
Why Pilots Care
Undetected disbonds can reduce structural strength and lead to failure under flight loads.
Analogy
It is like a sticker that still looks mostly in place, but part of it has lifted underneath. From a distance it may look attached, but the holding strength is reduced.
Intuition Check
A disbond is not just a surface scratch or a visible crack. It means the attachment between bonded layers has failed or started to fail, and it may be hidden under the surface.
Example Sentence 1
The inspector tapped along the rotor blade and found a disbond near the trailing edge where the skin had separated from the honeycomb core.
Example Sentence 2
During the preflight, a tap test indicated a possible disbond in the horizontal stabilizer skin.