Definition
A composite-material manufacturing and repair process in which a layup of resin and reinforcing fabric is sealed inside a flexible plastic bag, and the air is drawn out to apply atmospheric pressure evenly across the part while the resin cures. The pressure compacts the layers, removes trapped air, and squeezes out excess resin, producing a stronger, lighter, and more uniform finished piece.
Plain English
Putting a freshly laid-up composite part inside a sealed plastic bag and sucking the air out, so the surrounding air pressure presses everything together evenly while the glue hardens.
Context Anchor
Seen in aircraft maintenance, especially during composite structure repairs and composite part manufacturing.
Derivation
From the literal use of a bag — the part is placed inside a sealed plastic envelope. The technique is also called vacuum bagging because a vacuum pump draws the air out.
Why Pilots Care
Pilots flying composite aircraft, and owners arranging structural repairs, should know that proper bagging is what gives a composite part its designed strength. A repair done without it may look fine but be significantly weaker than the original structure.
Intuition Check
Bagging does not mean storing an aircraft part in a bag. Here it means sealing a repair under flexible film so vacuum or pressure can shape and compact it while it hardens.
Example Sentence 1
The repair shop used vacuum bagging to cure the new fiberglass patch on the wingtip.
Example Sentence 2
After bagging the fuselage, the fabric was doped to remove wrinkles and seal the surface.