Thermography

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INFRARED

THERMOGRAPHY

ON AIRCRAFT


Basic kit for the IRT control

Measurement chain

COMPAQ

V70

V70

(4)

(1)

(3)

(2)

Calibration

pieceheating 1- IR camera

2 – control panel of the camera

3 – Direct view on the screen

4 – Signal processing of the acquisition

INSTRUMENTATION


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)


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


IRT CONTROL ON COMPOSITE

transmission technique :

14 mm

carbon

rubber

Applied

Heat

Transmitted

Heat

Without defect With defect

T


IRT CONTROL ON COMPOSITE

Reflexion technique :

Emitted

Heat

Reflected

Heat

Absorbed

Heat

T

With defectWithout 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 a

honeycomb composite part

Reflexion method

Heating pulse : 0.1 sec


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


• 7 defects are detected

Transmission face 1

Defects 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


Phase Image Amplitude image

Method : reflexion heating, rubber side

Frequency : 0.006 Hz

Modulation : 1000 images



Method : transmission heating, rubber side



Phase imageAmplitude image



Disbonded area

A A

Cross section AA

rubber

aluminium

kevlar

bonding


Test sample, composite bonding Metal/Elastomer/Kevlar


Phase imageAmplitude Image


Method : transmission heating, kevlar side




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

Engineering

Thermography