Definition
Tiny hollow spheres of glass, plastic, or phenolic material, typically smaller than a grain of sand, mixed with a resin or epoxy to create a lightweight filler paste used in composite airframe repair and finishing.
Plain English
Very small hollow beads stirred into resin to make a light, easy-to-shape filler for fixing or smoothing composite aircraft parts.
Context Anchor
Seen in composite aircraft repair, surface filling, and fairing work during airframe maintenance.
Derivation
From 'micro' (very small) and 'balloon' (a hollow sphere filled with gas). The name describes what they are: microscopic hollow balls. Knowing this helps because their hollowness is exactly what makes the filler so light — the spheres are mostly air.
Why Pilots Care
Using microballoons keeps repaired parts light, preserving the aircraft’s original weight, balance, and performance.
Analogy
They work a little like adding tiny hollow beads to glue so the mix becomes lighter and easier to sand, instead of staying dense and hard.
Intuition Check
Microballoons are not balloons used for lifting. They are tiny hollow filler particles used inside repair material.
Example Sentence 1
The technician mixed microballoons with epoxy to fill the dent in the fiberglass cowling before sanding it smooth.
Example Sentence 2
After the resin cured, the microballoon mixture sanded smoothly without adding excess weight to the control surface.