A Rapid Optical Approach to Quantitative Composite Bond Quality Assessment

Widely used composite materials reduce aircraft weight and cost, improve structural performance, and boost fuel efficiency. However, composites are susceptible to adhesive bond line quality issues, both in initial fabrication and in service related bonding failures. Detection of weakened bonds requires an easy diagnostic approach to routinely monitor composite aircraft health. Our proposed solution combines a flexible bulk wave exciter, compact lightweight rapid zooming optical imaging device, and innovative processing. This approach can monitor an entire airframe, or zoom in to a specific joint and identify suspicious bonds by detecting areas of resonance or damping change resulting from a weakened bond. This technique, the Fast Imaging Non-Destructive Inspection Technique (FINDIT), directly and nondestructively tests the mechanical properties of composite bond lines. FINDIT quantitatively measures the associated surface tilt-tip changes and may be automated, removing subjective judgment factors. FINDIT can outline a hidden kissing bond and quantify the bond strength by measuring the bond mechanical damping properties. We envision commercial aircraft applications in production and normal hangar maintenance, as well as automotive safety, and other areas of composite application such as boats.