A Rapid Optical Approach to Quantitative Composite Bond Quality Assessment

Composite materials are widely used in aircraft to reduce weight and cost, improve structural performance, and boost fuel efficiency. However, composites are susceptible to adhesive bond quality issues, including kissing bonds which may occur because of initial fabrication or service related issues. Detection of such weakened bonds requires an easily used detection approach to routinely monitor composite health of military aircraft. We propose a solution based on three innovations, including this combination: a flexible movable mechanical bulk wave exciter that may be operated in impulse or chirped mode, and a compact lightweight rapid zooming optical imaging approach that can monitor any area from the complete airframe to a specific joint. We identify regions exhibiting suspicious bond quality by detecting the areas of resonance change or reduced damping, as a weakened bond reveals itself in response to mechanical excitation. This technique, called the Fast Imaging Non-Destructive Inspection Technique (FINDIT), can directly and nondestructively test the mechanical properties of composite material. FINDIT quantitatively measures the associated surface tilt-tip surface changes, and may be automated, removing subjective judgment factors. We envision commercial aircraft application in production and normal hangar maintenance, automotive safety, and other areas of composite application such as boats.