Thermograph y 1

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INFRARED

THERMOGRAPHYON AIRCRAFT


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Basic kit for the IRT control

Measurement chain

COMPAQ

V70

V70

(4)

(1)

(3)

(2)

Calibrationpieceheating 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, militaryapplication, ….

• Thermal sensitivity : (0,1 ° till 0,01 ° C)

• Acquisition frequency (25 till 300image/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, flashlamps, 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

AppliedHeat

TransmittedHeat

Wi t h o u t d e f e c t With defect

T



IRT CONTROL ON COMPOSITE

Reflexion technique :

EmittedHeat

ReflectedHeat

AbsorbedHeat

T

With defectWith out defect

14 mm

carbon

rubber

THERMOGRAM



Temperature variation in a point

Reflexion technique :

Transmission technique :

heating

T°

time

heating

T°

time

Without defect

With defect(isolation)



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



DEFECTS ENCOUNTERED

• Lack of adhesion of cohesion, bubbles

• Delamination

• Defects on surface coatings

• Inclusions of foreign materials

• Liquid ingress



Pulse heating method

Detection of defects inside ahoneycomb composite part

Reflexion method Heating pulse : 0.1 sec



Pulse method – reflexion inspection on part M88

• 7 defects visible

• Contrast isdecreasing afteroptimum image

Picture of part First image Heated part at T0

Optimum image 5 Sec after10 sec after

1 2

3 4 5



• 7 defects are detected

Transmission face 1Defects seen as dark spots

Reflexion face 1

Reflexion face 2

Transmission Vs Reflexion method



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 sideFrequency : 0.006 HzModulation : 1000 images



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Method : transmission heating, rubber sideFrequency : 0.003 HzModulation : 1000 images

Phase imageAmplitude image



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Disbonded area

A A

Cross section AA

rubber

aluminium

kevlar

bonding


Test sample, composite bonding Metal/Elastomer/Kevlar


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Phase imageAmplitude Image


Method : transmission heating, kevlar sideFrequency : 0.006 HzModulation : 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, productioncontrol)• 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

Documents

Thermograph y 1