Thermography NDT

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INFRARED
THERMOGRAPHY
ON AIRCRAFT

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Basic kit for the IRT control
Measurement chain
COMPAQ
V70
V70
(4)
(1)
(3)
(2)
Calibration
piece
heating 1- IR camera
2 – control panel of the camera
3 – Direct view on the screen
4 – Signal processing of the acquisition
INSTRUMENTATION

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Instrumentation used in IRT
Choice of the camera :
• Multiple use of the detector : IR night vision,
thermal control of active sources, military
application, ….
• Thermal sensitivity : (0,1° till 0,01°C)
• Acquisition frequency (25 till 300
image/s)
• Line acquisition mode or Focal Plane Array (FPA)

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Instrumentation used in IRT
Heating choices :
• Different techniques : hot air blower, tubes, flash
lamps, hot water, pulsed heating, laser, sun for
space shuttle, heating blanckets
• Surface heating or linear heating
• Homogeneity, reproductibility, calibration,
characterization

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IRT CONTROL ON COMPOSITE
transmission technique :
14 mm
carbon
rubber
Applied
Heat
Transmitted
Heat
Without defect With defect
T

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IRT CONTROL ON COMPOSITE
Reflexion technique :
Emitted
Heat
Reflected
Heat
Absorbed
Heat
T
With defectWithout defect
14 mm
carbon
rubber
THERMOGRAM

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Temperature variation in a point
Reflexion technique :
Transmission technique :
heating
T°
time
heating
T°
time
Without defect
With defect
(isolation)

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Thermographic Inspection
Advantages of the method :
• Global examination of part
• Only ONE SIDE access is required for the examination
• Real Time inspection
• Apply for all composite structure and materials even porous
• not very sensitive to part geometry, well suited for large surfaces
Disavantages :
• Sensitive to heating mode (type,duration,position)
• Response time must be studied
• Exact composition of the pieces and the thicknesses must be known
• Less definition than Ultrasonic C-Scan and Radiography
• Inhomogeneous heating on complex part

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DEFECTS ENCOUNTERED
• Lack of adhesion of cohesion, bubbles
• Delamination
• Defects on surface coatings
• Inclusions of foreign materials
• Liquid ingress

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Pulse heating method
Detection of defects inside a
honeycomb composite part
Reflexion method
Heating pulse : 0.1 sec

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Pulse method – reflexion inspection on part M88
• 7 defects visible
• Contrast is
decreasing after
optimum image
Picture of part First image Heated part at T0
Optimum image 5 Sec after 10 sec after
1 2
3 4 5

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• 7 defects are detected
Transmission face 1
Defects seen as dark spots
Reflexion face 1
Reflexion face 2
Transmission Vs Reflexion method

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Modulated thermography
440 mm
370 mm
carbon
14 mm
Test sample, composite bonding Carbon/Elastomer
rubber

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Phase Image Amplitude image
Method : reflexion heating, rubber side
Frequency : 0.006 Hz
Modulation : 1000 images
Modulated thermography

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Method : transmission heating, rubber side
Frequency : 0.003 Hz
Modulation : 1000 images
Phase imageAmplitude image
Modulated thermography

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Disbonded area
A A
Cross section AA
rubber
aluminium
kevlar
bonding
Modulated thermography
Test sample, composite bonding Metal/Elastomer/Kevlar

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Phase imageAmplitude Image
Modulated thermography
Method : transmission heating, kevlar side
Frequency : 0.006 Hz
Modulation : 3000 images

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Conclusions
• Global method, quick, well suited for detection on composite
and complex shaped surface, and for large areas
• Easy to set up on site (maintenance, expertise, production
control)
• Quick evolution of the technology, lower price of detectors,
new powerfull software for analysis tools will increase :
• maximum inspected thickness
• spatial and thermal resolution
• velocity of inspection