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Copyright Copyright © 2011 Envirocoustics SA 2011 Envirocoustics SA Health Monitoring of Composite Materials Rome Workshop Dr. Nikolaos Tsopelas Envirocoustics, Greece 28 th June 2011
Copyright Copyright ©© 2011 Envirocoustics SA2011 Envirocoustics SA
Health Monitoring of Composite Materials
Rome Workshop
Dr. Nikolaos TsopelasEnvirocoustics, Greece
28th June 2011
Copyright Copyright ©© 2011 Envirocoustics SA2011 Envirocoustics SA
According to ASTM (American Society for Testing and Materials), the term Acoustic Emission refers to “the class of phenomena whereby transient elastic waves are generated by the rapid release of energy from localized sources within a material, or the transient w aves so generated ”.
Definition and Basic Principles of Acoustic Emission
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The AE Sources
••METALSMETALS–– Plastic deformation, yielding, Plastic deformation, yielding,
creepcreep–– Crack growth (corrosion, Crack growth (corrosion,
fatigue), fatigue), microcrackingmicrocracking–– Stress corrosion crackingStress corrosion cracking–– Hydrogen Hydrogen embrittlementembrittlement–– Fracture / Fracture / decohesiondecohesion of of
inclusionsinclusions–– Phase transformations Phase transformations –– Corrosion processCorrosion process
REAL LIFE EXAMPLES (audible)REAL LIFE EXAMPLES (audible)
••IceIce--cube cracking in hot w atercube cracking in hot w ater
••Tearing of a piece of paperTearing of a piece of paper
••Bending of plastic rulerBending of plastic ruler
••Breaking of wooden pencilBreaking of wooden pencil
••COMPOSITESCOMPOSITES–– fibre/matrix fibre/matrix debondingdebonding–– fibre pullfibre pull--outout–– fibre fracturefibre fracture–– matrix matrix microcrackingmicrocracking–– delaminationdelamination–– creepcreep
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1. E 569-91 Standard Practice for Acoustic Emission Monitoring of Structures During Controlled Stimulation2. E 1316-94 Standard Definitions of Terms Relating to Acoustic Emission (now incorporated into E 1316)3. E 650-92 Standard Guide for Mounting Piezoelectric Acoustic Emission Sensors4. E 749-99 Standard Practice for Acoustic Emission Monitoring During Continuous Welding 5. E 750-93 Standard Practice for Characterizing Acoustic Emission Instrumentation 6. E 751-91 Standard Practice for Acoustic Emission Monitoring During Resistance Spot-Welding 7. E 976-94 Standard Practice for Determining the Reproducibility of Acoustic Emission Sensor Response8 . E 1002-94 Standard Method of Test ing for Leaks Using Ultrasonics 9. E1067-89 Standard Practice for Acoustic Emission Examination of Fiberglass Reinforced Plastic Resin (FRP)
Tanks/Vessels10. E 1106-92 Standard Method f or Primary Calibration of Acoustic Emission Sensors11. E 1118-89 Standard Practice for Acoustic Emission Examination of Reinforced Thermosetting Resin Pipe (RTRP)12. E 1139-92 Standard Practice for Continuous Monitoring of AE from Metal Pressure Boundaries13. E 1211-87 Standard Practice for Leak Detection and Location Using Surface-Mounted AE on Sensors14. E 1495-94 Acousto-Ultrasonic Assessment of Mechanical Properties of Composites, Laminates and Bonded
Joints15. E 1419-91 Test Method for Examination of Seamless, Gas Filled, Pr essure Vessels Using AE n16. F 914-85 Standard Test Method for Acoustic Emission for Insulated Aerial Personnel Devices17. E 1316-96 Terminology for Nondestructive Examination18. E 1736-95 Acousto-Ultrasonic Assessment of Filament-Wound/Pressure Vessels19. E 1781-96 Secondary Calibration of Acoustic Emission Sensors
(RED COLOUR DENOT ES COMPOSITES APPLICATION – Others exist as well e.g. ASME Article 11ASME Article 11FRP FRP VesselsVessels & Tanks& Tanks)
Some ASTM AE Codes and Standards
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l Damage (new surface formation) can occurl in the matrixl at the fiber/matri x interfacel across layersl by the breaking of fibers
••SOURCES in COMPOSITESSOURCES in COMPOSITES–– fibre/matrix fibre/matrix debondingdebonding–– fibre pullfibre pull --outout–– fibre fracturefibre fracture–– matrix matrix microcrackingmicrocracking–– delaminationdelamination–– impact (onimpact (on--line tests)line tests)–– creepcreep
AE in Composite Materials
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AE FROM COMPOSITES:• Plentiful• Increases exponentially towards failure• At high stress levels, occurs also during hold
and on repeat loading• AE is also detected from friction (old
damage) as well as new damage
AE in Composite Materials
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Attenuation and Velocit y Calculations
Attenuation and Velocity Investigation in 3 directions• Using WDI, R6a, R15, PICO and Mi cro 30 AE sensors• 0.5mm lead break s moving away from the s ensor in three directions
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• USING WDI, R6a, R15, PICO and Micro 30 AE sensors• 0.5mm lead break s moving away from the sensor in horizontal
direction
Attenuation Curve - GFRP - Horizontal Direction - All Sensors
35,00
40,00
45,00
50,00
55,00
60,00
65,00
70,00
75,00
80,00
85,00
90,00
95,00
100,00
0 50 100 150 200 250 300 350 400 450 500 550 600
Distance (mm)
Am
plitu
de (d
B)
Micro 30 Pico R6A R15 WDI Attenuation Curve - CFRP - Horizontal Direction - All Sensors
35,00
40,00
45,00
50,00
55,00
60,00
65,00
70,00
75,00
80,00
85,00
90,00
95,00
100,00
0 50 100 150 200 250 300 350 400 450 500 550 600
Distance (mm)
Am
plitu
de (d
B)
Micro 30 Pico R6 R15 WDI
Surprise! GFRP plate prefers R15, CFRP plate prefers R6.Surprise! GFRP plate prefers R15, CFRP plate prefers R6.
GFRP PlateGFRP Plate CFRP PlateCFRP Plate
Comparative Attenuation Curves
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Velocity Calculations
A B
R6a – HORIZONTAL DIRECTION
B
A
Position
3.289,92121,58122,25120,50122,00400
3.328,71120,17120,25119,75120,50400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
R6a – DIAGONAL DIRECTION
B
A
Position
3.308,06120,92121120,75121400
3.285,42121,75121,75121,75121,75400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
R6a – VERTICAL DIRECTION
B
A
Position
3.421,24116,92117117,75116400
3.404,25117,50117,75117,25117,50400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
R15a – HORIZONTAL DIRECTION
B
A
Position
3.305,79121,00121,00121,00121,00400
3.366,06118,83120,75119,75116,00400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
R15a – DIAGONAL DIRECTION
B
A
Position
3.256,45122,83122,75122,50123,25400
3.274,22122,17122,50121,75122,25400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
R15a – VERTICAL DIRECTION
B
A
Position
3.354,30119,25119,00119,50119,25400
3.373,16118,58118,00118,00119,75400
Velocity (m/sec)
Average Δt (μsec)Δt (μsec)
Source Distance
(mm)
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3 Point Bending Test Set -Up
87.5mm
1.3m 1
.0m
87.5mm
Support roller
75mm
Load roller
700m
m
700m
m
Delaminat ion
Impact
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3 Point Bending Test Set-Up AE and GW Sensors Locations
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3 Point Bending TestGFRP plate maximum deflection
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3 Point Bending TestPre-test - AE capture & Location of GW pulses
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3 Point Bending TestAE capture & Location of GW pulses During Test
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3 Point Bending TestAE During Test (LOAD INCREASES)
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3 Point Bending TestAE During Test (LOAD HOLDS)
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Tensile Test Setup
Tensile Test Specimen
800 mm
R15a – CH1
PICO – CH2
MFC - PULSER
MFC - RECEIVER
AE SENSORS SIDE MFCs SIDE
PICO – CH3
R15a – CH4
PICO sensor
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AE Amplitude vs Time during Loading to Failure
CH1 CH2 CH3 CH4
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AE Activity vs Time during Loading to Failure
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AE Activity vs Time during Cyclic Loading to Failure
CH1 CH2 CH3 CH4
AE Amplitude VS TimeAmplitudes of Linearly Located AE Events
AE Activity VS Time / Loading (kN) VS TimeAE Activity VS Time / Displacement (mm) VS Time
Kaiser and Felicity Effects
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Amplitude of Received Signals vs Time. Flat Lines Are GW Signals, All Other is Genuine Acoustic Emission
AE and GW Activity vs Time during Cyclic Loading to Failure
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GW Repetition
GW Waveforms as Acquired by different AE sensors in different positions
R15a
R15a
Pico
Pico
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Conclusions
l Experiments have demonstrated that the AE monitoring can be performed along w ith GW measurements w ithout interference of the GW to the AE monitoring.
l AE can detect and localize damage during health monitoring. It c an also discriminate the GW signals and locate the pulsing GW sensors.
l AE can provide a timel y warning of impending failure
l AE & Guided wave sensors can form a sensor -array providing additional & corroborative information w ithout degrading sensor performance
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Acknowledgement
12/7/2011 Footer text
ComPair Acknowledgement
ComPair is collaboration between the following organisations: TWI Ltd, Kaunas University of Technology, Technical Research Centre of Finland, National Technical University of
Athens, ATOUTVEILLE, Cereteth, G-Tronix Ltd, ENEA, ENVIROCOUSTICS, HEXCEL COMPOSITES, KINGSTON COMPUTER CONSULTANCY LIMITED.The Project is co-ordinated
and managed by TWI Ltd. and is partly funded by the EC under the Collaborative project programme- Small to medium scale focused research project. Grant Agreement Number
218697.
