Bond Repair: Making Surface Prep Measurable
Bonding composites is never simple, but repairing them is an entirely different challenge. Unlike pristine manufacturing environments where parts are prepped and assembled under controlled conditions, repairs often happen in less-than-ideal circumstances: an aircraft hangar, a wide-open warehouse, or even in the field.
In those environments, contamination risks skyrocket. Jet fuel residue, oil, grease, dust, and humidity are all potential threats to a successful bond. On top of that, repair technicians are working manually — sanding, cleaning, and prepping the surface by hand. Every extra stroke of sandpaper risks oversanding, exposing fibers, and reducing the long-term reliability of the repair.
Why Repair Bonding Is So Difficult
The Composite Materials Handbook (CMH-17), the global standard for composite design and repair, emphasizes that:
“Surface preparation is often the most critical factor in achieving a reliable bonded joint. Improper or inconsistent surface preparation can lead to reduced bond strength and premature failure.” — CMH-17, Vol. 3
The challenge comes down to three realities of repair work:
• Manual variability – No two technicians sand or prep exactly the same way.
• Uncontrolled environments – Field and hangar repairs are full of contaminants.
• Risk of oversanding – Exposed fibers make bonding worse, not better.
Measuring What Can’t Be Seen
In a recent demonstration with a leading aerospace composites team, Brighton Science’s technology was used to evaluate carbon fiber laminates under different prep conditions.
Figure 1: Prepped vs. unprepped surfaces in repair scenarios
Even with multiple operators and sample sources, the data consistently separated properly prepped from unprepped surfaces. This proves that prep quality can be validated objectively, not left to judgment calls.
Fiber Exposure: The Hidden Enemy
One of the most common repair pitfalls is sanding too aggressively. While it might look “clean,” oversanding can expose fibers — which reduces bond performance.
The CMH-17 warns: “Excessive abrasion can damage fibers, introduce defects, and reduce adhesion. Optimal preparation achieves a clean surface without compromising the composite substrate.” — CMH-17, Vol. 3
Figure 2: Fiber exposure increases contact angle
Measurements show that fiber exposure increases contact angle, reducing wettability and making surfaces less favorable for bonding. Our system makes this visible, helping technicians avoid the mistake.
Building Confidence in Repair Work
By validating surface prep with objective, real-time data, technicians gain confidence that their repairs are done right — even in tough conditions. The benefits include:
• Reliable confirmation before bonding
• Consistency across different operators
• Reduced risk of oversanding or contamination issues
• Alignment with industry standards like CMH-17
Bond repairs will always be challenging. But by making surface prep measurable, Brighton Science enables aerospace teams to ensure that every repair bond is strong, reliable, and built to last.
Learn More About Validating Composite Surface Prep
Ensuring every composite repair bond is reliable starts with understanding and validating surface preparation. For a deeper dive into best practices, including qualification of surface processes for bonded aircraft repair, check out our technical paper: Qualification of Surface Processes for Bonded Aircraft Repair.
Brighton Science provides the tools and data you need to make surface prep measurable — giving repair teams confidence that every bond will perform as intended.
