Definition
A reinforcement fabric, typically fiberglass, carbon, or aramid, that has been factory-saturated with a measured amount of uncured resin and stored under refrigeration until it is ready to be laid up and cured. Commonly called prepreg, it is used in the manufacture and repair of composite aircraft structures.
Plain English
Cloth that has already been soaked with the right amount of glue at the factory. The mechanic just lays it in place and heats it to harden, instead of mixing and brushing on resin by hand.
Context Anchor
Seen in aircraft composite maintenance, especially when describing materials used to make or repair panels, fairings, cowlings, and other composite parts.
Derivation
Pre- means before, and impregnated means soaked through. So the fabric is soaked through with resin before it ever reaches the technician.
Why Pilots Care
Prepreg parts give consistent strength because the resin-to-fabric ratio is controlled at the factory, but the material has a limited shelf life and must be kept cold until use. A repair made with mishandled or expired prepreg may not develop full strength.
Grounding Statement
Picture a flexible sheet of strong fabric that already has the glue-like material inside it, waiting to be shaped and hardened.
Intuition Check
Preimpregnated does not mean the fabric is already finished or fully hardened. It means the fabric already contains the resin and still must be properly cured before the part is complete.
Example Sentence 1
The repair station kept the preimpregnated fabric in a freezer until the cowling repair was ready to be laid up.
Example Sentence 2
Preimpregnated fabric allowed the repair crew to control resin content without additional mixing steps.