Colorimetric Primer Thickness Prediction for Aerospace Bonding
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Solution Overview
Problem
The difficulty in accurately detecting the thin thickness of structural adhesive bond primers on anodized aluminum substrates for aerospace components, which affects bond performance and corrosion resistance, due to limited sensitivity of measurement devices and operator detection capabilities.
Innovation Solution
A method using colorimetric analysis with an L*a*b* color scale to measure the performance of epoxy-functional coatings, involving exposure to a corrosive environment, and correlating colorimetric values with bond primer thickness to predict corrosion inhibition and bond strength, with a primer thickness range of 0.1 to 0.5 mil, including hexavalent chromium and dyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement devices and visual inspection are used to detect primer thickness, then the measurement process is simple, but the measurement precision is insufficient for thin films below 0.50 mil
Solution Approach 1:
The patent replaces mechanical thickness measurement devices with optical colorimetric analysis. A spectrophotometer measures color values (L*a*b*) of the primer coating, and through calibration curves, these optical measurements are converted to thickness predictions. This substitution enables precise measurement of thin films below 0.50 mil that are undetectable by traditional mechanical gauges or visual inspection.
2Reliability
If operator visual detection is used to assess primer thickness, then the method is easy to operate, but the reliability is insufficient due to operator variability and limited sensitivity
Solution Approach 1:
The system enables self-service measurement where the spectrophotometer automatically measures color values and the calibration curve automatically converts these to thickness predictions without requiring operator expertise. The objective colorimetric analysis eliminates subjectivity and variability inherent in visual inspection, providing consistent, reliable measurements that are as easy to perform as visual assessment.
3Strength
If primer thickness is not accurately controlled, then the coating application process is faster, but the bond strength and corrosion resistance deteriorate
Solution Approach 1:
The patent implements preliminary colorimetric measurement and thickness prediction before bonding operations. By measuring the primer's color values and predicting thickness upfront, the system ensures proper primer application before proceeding to bonding, preventing rework due to insufficient or excessive primer thickness. This preliminary verification maintains high productivity by avoiding delays from inadequate primer preparation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables accurate prediction of bond performance and corrosion resistance, ensuring robust and reliable bonded aerospace structures by verifying bond primer thickness and corrosion inhibiting properties, improving the reliability of bonded joints.
Implementation Method 1
measuring the bond primer thickness and colorimetric properties using a colorimetric method
Implementation Method 2
evaluating the coated substrate using colorimetric analysis
Data Source
AI summary
A method for measuring performance of a film coated onto a substrate is disclosed, including exposing a coated substrate to a corrosive environment, evaluating the coated substrate using colorimetric analysis, quantifying the colorimetric analysis. The method also includes determining a coating performance attributes, corrosion resistance and bond strength, based on the colorimetric analysis. Also disclosed is a method of applying a coating to a substrate, including applying a primer to a surface of a substrate, curing the primer at an elevated temperature, and measuring a surface of the primer coated substrate with a spectrometer.