Introduction
Adhesion failures are among the most common yet preventable issues in composite bonding, coatings, and sealants. Whether in aerospace, automotive, or medical manufacturing, poor surface preparation can lead to structural weaknesses, warranty claims, and costly rework. But what if the real issue isn’t the materials or adhesives—it’s the lack of a reliable way to measure surface quality?
For decades, manufacturers have relied on water break tests, dyne inks, and subjective visual checks to assess surface quality. However, these methods fail to provide objective, real-time insights. Today, forward-thinking companies are turning to Water Contact Angle (WCA) measurement to establish adhesion specifications, monitor process drift, and improve technician training.
In this article, we’ll explore:
- Case studies showing how manufacturers solved real adhesion challenges.
- How WCA helps detect process drift before failures occur.
- How technician training impacts adhesion performance.
Real-World Case Studies: How Manufacturers Are Using WCA to Solve Adhesion Issues
Case Study: Process Drift Detection in Composite Bonding
The Problem
An aerospace manufacturer was experiencing an alarming increase in bond failures in a critical composite structure. Despite following their standard surface preparation process, inconsistencies in adhesion performance were appearing across production batches.
Technicians were frustrated. Quality engineers were at a loss. Every test showed that nothing had changed in their process—yet adhesion failures were rising, adding millions in rework and material waste.
To complicate matters, water break tests were still passing on these surfaces, falsely indicating that they were clean and bondable.
Investigation
The company introduced Water Contact Angle (WCA) measurement at critical checkpoints to evaluate the true state of surface quality before bonding.
The data revealed an unsettling trend: contact angles had been gradually increasing over time, creeping from a bond-ready 20° to a risky 50°, even though nothing had officially changed in the process.
This increase in contact angle pointed to contaminant buildup over time, something that had gone undetected because standard visual inspections and water break tests weren’t sensitive enough to catch it.
Solution
By implementing WCA as a quality control metric, the manufacturer was able to identify the source of contamination—a slight variation in their solvent wipe process that had developed over time. Adjustments were made, and a continuous monitoring system was put in place to detect future process drift before it impacted bond strength.
As a result, bond failures were eliminated, and the company saved millions in scrap and rework costs by ensuring every composite structure met adhesion requirements before it reached final assembly.
Watch the on-demand webinar Establishing and Monitoring Adhesion Specifications:
Ensuring Bond Quality Throughout the Product Lifecycle to learn how manufacturers are using Water Contact Angle data to stop bond failures before they start.
Case Study: Hidden Contamination in Surface Abrasion
The Problem
At a military aircraft repair depot, technicians were struggling to get reliable bond strength when making structural repairs to composite surfaces. Even after rigorous surface preparation—including sanding and solvent wiping—their adhesive joints were failing at an unacceptable rate.
The technicians were performing the same steps they always had, and every visual inspection suggested the surfaces were properly prepared. But when tested, the bonds failed again and again, raising concerns about long-term aircraft durability.
Investigation
To better understand what was happening, WCA measurements were introduced before and after the sanding process. The results were startling—even freshly sanded surfaces were showing high contact angles (80°+), indicating poor surface quality.
How could this be?
A deeper investigation revealed that the sandpaper itself was the problem. Many commercially available sanding discs contained anti-clogging additives—materials designed to prevent the paper from becoming loaded with debris. While these additives helped extend the life of the sandpaper, they also left behind an invisible contamination layer on the composite surface—a layer that completely disrupted adhesion.
Solution
Once this issue was identified, the depot switched to an approved list of abrasives that were free of adhesion-inhibiting contaminants. Technicians were retrained, and WCA testing became part of the standard surface prep validation process before bonding.
This single discovery drastically improved bond reliability, ensuring that critical repairs could be trusted for the life of the aircraft.
Case Study: Training Variability Among Technicians
The Problem
A manufacturer producing composite automotive parts was facing an unusual challenge—bond failures were occurring unpredictably, and they weren’t linked to any specific batch of materials.
Upon deeper investigation, it became clear that the same process, same materials, and same adhesives were yielding different adhesion results, depending on which technician performed the surface preparation.
This inconsistency led to mounting production delays, wasted materials, and frustrated engineers who couldn’t pinpoint the exact cause of the failures.
Investigation
WCA measurements were used to compare surface quality before and after manual abrasion—but with a new focus: not just measuring the surfaces, but measuring the technicians.
The results were striking:
Technician A consistently produced surfaces with WCA readings in the optimal range (35°-40°), leading to strong bonds.
Technician B's surfaces averaged much higher contact angles (60°+), meaning poor adhesion.
The process wasn’t the problem—the way it was being executed varied from person to person.
Solution
To address this, the company used WCA as a training and certification tool, giving technicians immediate feedback on their technique. Those who needed improvement were coached on proper abrasion pressure, duration, and wiping techniques.
By standardizing training based on measurable surface quality data, the company eliminated variability, ensuring that every technician, across every shift, prepared surfaces correctly.
This led to a dramatic increase in bonding reliability, reducing defects and ensuring that every product leaving the factory met adhesion requirements.
Optimizing Adhesion: From Process Control to Predictable Performance
For manufacturers, adhesion failures often stem from hidden variables in surface preparation—not the adhesive itself. Contaminants, process drift, and technician variability all introduce risks that traditional methods like water break tests and dyne inks fail to detect. Without objective, quantifiable data on surface quality, manufacturers are left troubleshooting failures instead of preventing them.
To eliminate uncertainty and gain control over bonding, coating, and sealing processes, manufacturers must implement real-time, data-driven surface quality monitoring. By integrating Water Contact Angle (WCA) measurement into their workflow, they can:
✔ Detect process drift before failures occur
✔ Establish adhesion specifications backed by ASTM standards
✔ Standardize technician training to eliminate variability
✔ Ensure every bonded component meets quality requirements before final assembly
To learn how your organization can take a proactive approach to adhesion control, download the eBook The Future of Manufacturing: A Guide to Intelligent Adhesive Bonding Technologies & Methodologies.
