Issue << content << Active Thermography — a Powerful Non-Destructive Method for Large-Sized Composite Products Testing


DOI: 10.12737/18031

2016. Vol.19. No. 1, pp. 8-12

Active Thermography — a Powerful Non-Destructive Method for Large-Sized Composite Products Testing

M. Wandelt, T. Kröger, M. Johannes

The necessity of non-contact highly efficient method for non-destructive testing of large-sized composite products resulted in the rapid progress in active thermography systems creation. By applying an appropriate mathematical analysis to the recorded temperature data, defects in the interior of the component, such as delaminations, cracks and water inclusions, become visible. The article gives a detailed review of active thermography measurement methods including pulse-thermography, step heating thermography, lock-in thermography, and vibrothermography. The main principles of the methods and applied testing techniques are considered by the examples of aerospace composite products inspection.
As an example the application of active thermography techniques for detection of disbonds between the fuselage skin and doublers of the Boeing B737 as well as inspection for ice and water inclusions in its honeycomb parts are described. The efficiency of honeycomb sandwich structures of military and civil aircrafts by applying the active thermography is shown by the comparison with an ultrasonic phased array testing technique applied to the same objects.
Large-area inspections have often been associated with great effort and high costs. The advantages of the technique are evident: it enables non-contact inspection of large areas, the required measurement times are short and the results are displayed as high-resolution images. A single measurement can cover an area of up to 1m2. This novel systems enable inspections to be performed much faster, greatly reducing inspection time and aircraft downtime. The presentation of results as high- resolution images enables reliable identification of defects and reduces the dependence on the human factor.
The system is particularly suitable for inspecting the latest-generation aircraft.

Keywords: thermal testing, active thermography, aerospace engineering, composite
References:
1. ASNT, Nondestructive Testing Handbook, Third Edition: V. 3. Infrared and Thermal Testing. — Columbus, Ohio: American Society for Nondestructive Testing, Inc., 2001, pp. 318–338.
2. ASTM E2582-07(2014 Standard Practice for Infrared Flash Thermography of Composite Panels and Repair Patches Used in Aerospace Applications.
3. AIA, NAS-410: National Aerospace Standard 410 rev. 3, NAS Certification & Qualification of Nondestructive Test Personnel, Aerospace Industries Association.
 
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