Plain English Meaning
A strong glue-like liquid that hardens into tough plastic. In composite parts, it locks the fibers together so the whole piece acts as one solid structure.
Full Definition
A two-part synthetic adhesive used as the binding matrix in composite aircraft structures. When mixed with a hardener, the liquid resin cures into a strong, rigid plastic that holds reinforcing fibers (such as fiberglass, carbon, or aramid) in place and transfers loads between them.
Context Anchor
Seen in discussions of composite aircraft structures, fiberglass or carbon-fiber parts, and approved composite repairs.
Derivation
From Greek 'epi' (upon) and 'oxy' (from oxygen), referring to the chemical structure of the resin. 'Resin' originally meant tree sap — a sticky substance that hardens over time. The name fits: epoxy starts sticky and cures into something rigid.