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Smart Composites
Monitoring composite structures with optical fibers
Geert Luyckx
Damien Kinet

© sirris | www.sirris.be |...
Overview
Life1. Objective
cycle of a composite structure
Production and assembly monitoring
2. Rationale
A. Production and...
MANUFACTURING

Life cycle of a composite structure
Use Phase

Assembly
Assembly
Assembly
Assembly
“Life cycle monitoring o...
Life cycle monitoring: Wind turbine
Life cycle monitoring: Wind turbine
Production

Assembly

Design

Exploitation
Production monitoring & opportunities
Production

Today
Thermocouples
Pressure sensors
Ultrasonic inspection
No sensor abl...
Technology: Fiber Bragg Gratings
Combination of Optical fibers and Ultrasound

Optical fiber
Combination of Optical fibers and Ultrasound
1

Gelation

2
Temperature

FBG strain
Residual strain magnitude
Ultrasound

...
Assembly monitoring & opportunities
Assembly
+
Finishing

Today
Visual inspection
Opportunities
Embed sensors in adhesive ...
Follow-up of bonded structures

Initiated cracks reach sensor

Safety level
Application monitoring & opportunities
Design

Today
Visual inspection
Load monitoring (edge, flap, combined)
External str...
Pitch control monitoring
MOOG inc: System to Adjust
Windmill Wing Pitch Angle

Provide edgewise and flap
wise bending mome...
Composite life cycle monitoring: Opportunities
Difficulties
Read-out and integration
Cost and size of interrogator system
...
Novel sensor technologies
Micro-structured optical fibers

Polymer waveguides

Deformable electronics
Dr. ir. Geert Luyckx
Geert.Luyckx@UGent.be
+32 486 95 32 04

12/5/2013

16
Structural Health Monitoring
applied to Marine Applications
Structural Health Monitoring
applied to Marine Applications
Development of FBG sensors based on silica &
plastic optical f...
Structural Health Monitoring
applied to Marine Applications
Developing low cost optical interrogator
Physical validation f...
Structural Health Monitoring
applied to Marine Applications

Sensor
Evolution

Simulation

Sensor
Interrogation

Sensor
Em...
Preliminary tests
• More then 60 FBGs were glued on the catamaran mast
• FBGs realized by the phase mask technique.
• Chir...
Preliminary tests

Fibre n°1
Fibre n°3

Fibre n°2

Fibre n°4

Fibres n°2, 5
and 8
Fibre n°6

Fibre n°5

Fibres n°1,
4 and ...
Preliminary tests

Naked mast
Preliminary tests

Fibre maintained on the
mast with tape
Preliminary tests

FBGs are glued on the mast
with epoxy resin
Preliminary tests

Mast with FBGs
Preliminary tests

Mast is let free and is only maintained at both extremities
Preliminary tests

Schematic representation of the mast during this test

We follow the evolution of the Bragg wavelength ...
Bragg	wavelength	shift	
(pm)	

Preliminary tests
0
y	=	-3E-10x4	+	1E-06x3	-	0.0012x2		
-	0.078x	-	19.343	
R²	=	0.92681	

-...
Preliminary tests

Mast is let free and is only maintained at both
extremities but turned on its side
Preliminary tests
We follow the evolution of the Bragg wavelength of the FBGs.
As expected:
The Bragg wavelength shifts of...
2nd phase: Embedding

- Realisation of small
grooves
- Optical fibers embedding
- Filling of the grooves and
protection of...
2nd phase: Embedding

Splicing of the optical fibers

Ingress/egress
of the optical fibers
2nd phase: Embedding
MPO (Multi-fiber Push-On) connector
between the mast and the interrogator

Rapid prototyping of a wat...
Interrogator set-up

FBG 1

FBG x

FBG 1

FBG x

FBG 1

FBG x

Optical circulator

…

e-LED

Photodiode &
Data processing
...
Interrogator set-up

Light, small size, low power consuming
Damien KINET
Damien.KINET@umons.ac.be
+32 (0) 65 37 41 96

© sirris | www.sirris.be | info@sirris.be |

5.12.13
SBO Self sensing composites
Production
monitoring

Structural
health
monitoring
Case: control arm
2 optical fibers, 10 sensors
Designed and manufactured by
and

12/5/2013

39
http://www.sirris.be
http://techniline.sirris.be
#sirris
http://www.linkedin.com/company/sirris
© sirris | www.sirris.be |...
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2013 12-05-sirris-materials-workshop-smart-composites-luyckx-kinet

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Sirris Materials Workshop - 5 december 2013 -
Monitoring composite structures with fibre optic sensors -
Geert Luyckx, UGent and Damien Kinet, Multitel

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2013 12-05-sirris-materials-workshop-smart-composites-luyckx-kinet

  1. 1. Smart Composites Monitoring composite structures with optical fibers Geert Luyckx Damien Kinet © sirris | www.sirris.be | info@sirris.be | 5.12.13 1
  2. 2. Overview Life1. Objective cycle of a composite structure Production and assembly monitoring 2. Rationale A. Production and Application monitoring assembly monitoring B. Operation/Health monitoring Opportunities 3. Sensor technologies Novel Envisaged applications 4. technologies 5. Research consortium 6. Research Applications approach 7. Industrial user consortium Health monitoring in marine environment
  3. 3. MANUFACTURING Life cycle of a composite structure Use Phase Assembly Assembly Assembly Assembly “Life cycle monitoring of large-scale CFRP VARTM structure by fiber-optic-based distributed sensing,” S. Minakuchi, et. al., Composites Part A, 42(6),669-676 (2011)
  4. 4. Life cycle monitoring: Wind turbine
  5. 5. Life cycle monitoring: Wind turbine Production Assembly Design Exploitation
  6. 6. Production monitoring & opportunities Production Today Thermocouples Pressure sensors Ultrasonic inspection No sensor able to predict initial strain state! Opportunities Initial strain state (residual strains) e.g. with embedded sensors (Fiber optics, Polymer waveguides,…) In-situ Cure monitoring e.g. with ultrasonic transducers, Fresnel reflection, capacitive sensing,… NECESSITY FOR MULTI-INSTRUMENTATION
  7. 7. Technology: Fiber Bragg Gratings
  8. 8. Combination of Optical fibers and Ultrasound Optical fiber
  9. 9. Combination of Optical fibers and Ultrasound 1 Gelation 2 Temperature FBG strain Residual strain magnitude Ultrasound 2 regions: 1. Composite does not exist! Resin in a fluid state 2. Composite exist strain transfer
  10. 10. Assembly monitoring & opportunities Assembly + Finishing Today Visual inspection Opportunities Embed sensors in adhesive zone Use finishing layer as sensor (coating)? Ageing sensors? Impact damage, tool drop Speed of monitoring event measurement or offline monitoring
  11. 11. Follow-up of bonded structures Initiated cracks reach sensor Safety level
  12. 12. Application monitoring & opportunities Design Today Visual inspection Load monitoring (edge, flap, combined) External strain gauges No information from the inside Exploitation Opportunities Pitch control (blade deformation) predict life time blades Use material as sensor (CNT, CB,…), Digital Image Correlation? Design support tool Reduce costly inspection
  13. 13. Pitch control monitoring MOOG inc: System to Adjust Windmill Wing Pitch Angle Provide edgewise and flap wise bending moment data to the individual pitch control system. 10-20% of load reduction in the blades 20-30% in the main shaft Life time ↑↑ www.moog.com/markets/ energy/wind-turbines/
  14. 14. Composite life cycle monitoring: Opportunities Difficulties Read-out and integration Cost and size of interrogator system Go for less performing system? More dedicated? Cheaper? Number of sensors needed to monitor structure? The least possible (design or exploitation) Reparability: Sensor should survive the structure with 100% certainty or possibility for repair Prediction of Eigenfrequencies via online strain date Relation of the sensor signal with the real situation
  15. 15. Novel sensor technologies Micro-structured optical fibers Polymer waveguides Deformable electronics
  16. 16. Dr. ir. Geert Luyckx Geert.Luyckx@UGent.be +32 486 95 32 04 12/5/2013 16
  17. 17. Structural Health Monitoring applied to Marine Applications
  18. 18. Structural Health Monitoring applied to Marine Applications Development of FBG sensors based on silica & plastic optical fibres Investigating sensor embedding processes and positioning the optical fibres at different layers according to the strains to monitor Developing a complete catamaran in carbon fibre reinforced polymer which will be used for further investigation and embedding of smart components
  19. 19. Structural Health Monitoring applied to Marine Applications Developing low cost optical interrogator Physical validation for finite element simulation • Real-time strain monitoring • Composite material properties investigation • Broken down and failure detection
  20. 20. Structural Health Monitoring applied to Marine Applications Sensor Evolution Simulation Sensor Interrogation Sensor Embedding Sensor Fabrication
  21. 21. Preliminary tests • More then 60 FBGs were glued on the catamaran mast • FBGs realized by the phase mask technique. • Chirped phase mask: 15nm/cm, length of each FBG: 1mm Shrouds Fibre Bragg gratings Location of the future housing connectors Spreader 1.10m 0.70m 0.70m 8.90m 9.25m 15.25m 17.75m Front view: Schematic representation
  22. 22. Preliminary tests Fibre n°1 Fibre n°3 Fibre n°2 Fibre n°4 Fibres n°2, 5 and 8 Fibre n°6 Fibre n°5 Fibres n°1, 4 and 7 Fibres n°3, 6 and 9 350 mm 190 mm Shape of the mast base Fibre n°7 Fibre n°9 Fibre n°8 Location of the future housing connectors Base of the mast
  23. 23. Preliminary tests Naked mast
  24. 24. Preliminary tests Fibre maintained on the mast with tape
  25. 25. Preliminary tests FBGs are glued on the mast with epoxy resin
  26. 26. Preliminary tests Mast with FBGs
  27. 27. Preliminary tests Mast is let free and is only maintained at both extremities
  28. 28. Preliminary tests Schematic representation of the mast during this test We follow the evolution of the Bragg wavelength of the FBGs. As expected: The Bragg wavelength shifts of the FBGs of the fibres n°1, 3, 4, 6, 7 and 9 are very small The FBGs of the fibres n° 2, 5 and 8 are under compression
  29. 29. Bragg wavelength shift (pm) Preliminary tests 0 y = -3E-10x4 + 1E-06x3 - 0.0012x2 - 0.078x - 19.343 R² = 0.92681 -100 -200 -300 -400 -500 0 500 1000 Position (cm) 1500 This figure presents the shift of the Bragg wavelength of the FBGs of the fibres n° 2, 5, 8 with an attempt to adjust a curve of the 4th order
  30. 30. Preliminary tests Mast is let free and is only maintained at both extremities but turned on its side
  31. 31. Preliminary tests We follow the evolution of the Bragg wavelength of the FBGs. As expected: The Bragg wavelength shifts of the FBGs of the fibres n°1, 4 and 7 are under traction. The Bragg wavelength shifts of the FBGs of the fibres n°3, 6 and 9 are under compression. Bragg wavelength shift (pm) Fibre n°4 Fibre n°6 600 400 200 0 -200 -400 -600 1 3 5 N° of the FBG 7
  32. 32. 2nd phase: Embedding - Realisation of small grooves - Optical fibers embedding - Filling of the grooves and protection of the sensors with epoxy glue
  33. 33. 2nd phase: Embedding Splicing of the optical fibers Ingress/egress of the optical fibers
  34. 34. 2nd phase: Embedding MPO (Multi-fiber Push-On) connector between the mast and the interrogator Rapid prototyping of a waterproof housing for the connection. This one will be attached to the mast
  35. 35. Interrogator set-up FBG 1 FBG x FBG 1 FBG x FBG 1 FBG x Optical circulator … e-LED Photodiode & Data processing Tunable filter Light, small size, low power consuming
  36. 36. Interrogator set-up Light, small size, low power consuming
  37. 37. Damien KINET Damien.KINET@umons.ac.be +32 (0) 65 37 41 96 © sirris | www.sirris.be | info@sirris.be | 5.12.13
  38. 38. SBO Self sensing composites Production monitoring Structural health monitoring
  39. 39. Case: control arm 2 optical fibers, 10 sensors Designed and manufactured by and 12/5/2013 39
  40. 40. http://www.sirris.be http://techniline.sirris.be #sirris http://www.linkedin.com/company/sirris © sirris | www.sirris.be | info@sirris.be | 5.12.13

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