Definition
A method of fabricating or repairing composite structures in which dry reinforcement fabric (such as fiberglass, carbon, or aramid cloth) is laid into or onto a mold or part, and liquid resin is then applied and worked into the fabric by hand using brushes, rollers, or squeegees. The resin saturates the fibers in place, and the assembly is allowed to cure, bonding the fibers into a rigid composite layer.
Plain English
A repair or build-up technique where the cloth is placed first and then wet down with liquid resin on the spot, instead of using cloth that already has resin built into it.
Context Anchor
Seen in aircraft composite repair, fiberglass work, fairing repairs, and maintenance instructions for non-metal aircraft parts.
Derivation
Wet' refers to the liquid resin being added at the time of layup, and 'lay-up' refers to laying layers of fabric in place. The term distinguishes this method from a 'pre-preg' lay-up, where the fabric arrives already pre-impregnated with resin and is simply laid in place before curing.
Why Pilots Care
Ensures proper bonding and strength in composite airframe repairs, critical for maintaining structural integrity and airworthiness.
Intuition Check
Do not read “wet” as water-soaked. In this term, “wet” means the fabric is saturated with liquid resin that will harden.
Example Sentence 1
The mechanic performed a wet lay-up to repair the cracked fiberglass wingtip, applying three layers of cloth and resin over the damaged area.
Example Sentence 2
Wet lay-up techniques require careful control of resin-to-fiber ratio to achieve the desired strength.