Definition
A type of damage to honeycomb sandwich structure in which the lightweight cellular core has been crushed or compressed, collapsing the cell walls and reducing the structural strength and stiffness of the panel.
Plain English
The thin honeycomb material sandwiched inside a composite panel has been squashed flat in one area, so the panel is no longer as strong or stiff as it should be there.
Context Anchor
Seen in aircraft maintenance and inspection discussions, especially with composite panels, honeycomb panels, fairings, control surfaces, and other lightweight aircraft structures.
Derivation
Core refers to the inner honeycomb layer of a sandwich panel, sandwiched between two thin face skins. Crush is used in its everyday sense of being compressed or collapsed under force. Together the term names exactly what has happened: the inner layer has been pressed in.
Why Pilots Care
Undetected core crush can lead to delamination or structural failure under flight loads.
Analogy
Think of a cardboard door or a hollow-core door. The outside surface may look mostly intact, but if the inside has been crushed, the door loses much of its strength.
Intuition Check
Do not assume core crush means only surface damage. It specifically means the inner supporting material has been crushed, which can hide under a small dent or mark.
Example Sentence 1
During the post-flight inspection, the mechanic found core crush on the underside of the flap where a maintenance stand had been pressed against it.
Example Sentence 2
Core crush in a rotor blade requires repair before the next flight.