Time is running out. A handbook covering composite repairs is free on Kindle, with three other titles, until Tue 10 Nov 23:59 PT. Time remaining: ends Tue 10 Nov, 11:59 pm PT.
This repair explainer was published during a free Kindle week for four engineering books in November 2026.
A dented aluminium skin can often be blended out or patched by a trained mechanic with familiar tools. Carbon fibre is less forgiving. Damage may be hidden, and a repair has to restore strength that was built into the original stack of plies. So the process starts with finding out what actually happened.
Finding the damage
A surface mark on a laminate says little about what lies beneath. Technicians start with a visual check, then use non-destructive inspection to map internal damage. Ultrasonic methods are common, since sound waves reflect differently from a delamination. Simple tap tests can also find larger disbonds. The result is a map of the damaged area, which usually proves larger than the visible mark.
Deciding what to do
Airlines work from the manufacturer's structural repair manual, which sets out allowable damage limits. Small damage might only need sealing and monitoring. Larger damage calls for a defined repair. Anything beyond the manual's limits goes to engineers for a specific assessment.
Bolted repairs
A bolted repair fastens a pre-cured patch or a metal plate over the damage. It's relatively quick, it tolerates less controlled conditions and it can be inspected. On the downside, it adds holes, weight and a bump in the surface.
Bonded repairs
A bonded scarf repair is more elegant. The damaged material is removed, and the surrounding laminate is ground to a shallow taper. New plies are laid in, matching the original direction, and cured under heat and vacuum. The result can be smooth and efficient.
However, it demands strict control. Surface preparation, moisture and temperature all affect the bond, and a poor bond is hard to see. That's why such repairs need trained staff and controlled conditions, and why bonded joints get so much scrutiny.
Designed with repair in mind
Maintainability now starts on the drawing board. Engineers consider where damage is likely and how it would be reached. A structure that's light but impractical to fix can cost an operator more over its life.
The four books
Practical Airframe Stress Analysis, Volume 2: Composite Structure
GD&T Professional Exam Guide
Practical Airframe Stress Analysis, Volume 1: Metallic Structure
Python for Aerospace Stress Engineers (Volume 3)
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Related gear
- Practical Airframe Stress Analysis, Volume 2: Composite Structure (Sandeep Bandyopadhyay) on Amazon — Related gear
- Aero Structures and Composite Materials with Artificial Intelligence (book) — Sandeep's book
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