Definition
Structural weakening or failure of composite aircraft materials caused by exposure to elevated temperatures, where the resin matrix softens, melts, or chars and loses its ability to bind the reinforcing fibers together. Heat damage in composites can occur from sources such as engine bay heat, lightning strikes, brake fires, exhaust impingement, or even a parked aircraft sitting in direct sun under a dark paint scheme, and the damage is often invisible from the surface.
Plain English
When a composite part gets too hot, the glue holding the strong fibers together starts to break down. The part can look fine on the outside but be much weaker than it should be.
Context Anchor
Seen during preflight or maintenance inspections of composite aircraft parts, especially near exhaust areas, engine covers, brakes, or after a fire or overheating event.
Why Pilots Care
Undetected heat damage can reduce load-carrying capability and lead to sudden structural failure under flight loads.
Analogy
It is like a plastic tool left too close to a heater: it may still look like the same tool, but the heat can make it softer, warped, or less trustworthy.
Grounding Statement
If an aircraft part has been exposed to more heat than it was designed to handle, its strength may be reduced even without a large visible burn mark.
Intuition Check
Heat damage does not only mean obvious fire damage or black burn marks. In composites, too much heat can weaken the material inside before the outside looks seriously damaged.
Example Sentence 1
After the brake fire was extinguished, the mechanic flagged the composite wheel pant for heat damage inspection before the aircraft was returned to service.
Example Sentence 2
Lightning strikes can create localized heat damage in composite wings that requires ultrasonic testing to detect.