Smart CompositesMonitoring composite structures with optical fibers
Geert Luyckx
Damien Kinet
15.12.13© sirris | www.sirris.be | [email protected] |
1. Objective2. Rationale
A. Production and assembly monitoringB. Operation/Health monitoring
3. Sensor technologies4. Envisaged applications5. Research consortium6. Research approach7. Industrial user consortium
� Life cycle of a composite structure
� Production and assembly monitoring
� Application monitoring
� Opportunities
� Novel technologies
� Applications
� Health monitoring in marine environment
Overview
Life cycle of a composite structure
“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)
MA
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UseUseUseUse PhasePhasePhasePhase
Life cycle monitoring: Wind turbine
Assembly
Exploitation
DesignProductionProductionProductionProduction
Life cycle monitoring: Wind turbine
Production monitoring & opportunities
ProductionProductionProductionProduction 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
ProductionProductionProductionProduction
Technology: Fiber Bragg Gratings
Optical fiberOptical fiberOptical fiberOptical fiberOptical fiberOptical fiberOptical fiberOptical fiber
Combination of Optical fibers and Ultrasound
Combination of Optical fibers and Ultrasound
2 regions:1. Composite does not exist! Resin in a fluid state2. Composite exist � strain transfer
1111 2222Gelation
Ultrasound
Temperature
FBG�strain
Residual strain magnitude
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
Follow-up of bonded structures
Initiated cracks reach sensor
Safety level
Exploitation
Design
Application monitoring & opportunities
Today� Visual inspection
� Load monitoring (edge, flap, combined)
� External strain gauges
No information from the inside
Opportunities� Pitch control (blade deformation)
� predict life time blades
� Use material as sensor (CNT, CB,…), Digital Image Correlation?
� Design support tool
� Reduce costly inspection
Pitch control monitoring
� MOOG inc: System to Adjust Windmill Wing Pitch Angle
www.moog.com/markets/energy/wind-turbines/
� 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 ↑↑
� 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 Eigenfrequenciesvia online strain date
� Relation of the sensor signal with the real situation
Composite life cycle monitoring: DifficultiesOpportunities
� Micro-structured optical fibers
� Polymer waveguides
� Deformable electronics
Novel sensor technologies
Structural Health Monitoringapplied to Marine Applications
Structural Health Monitoringapplied 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
Structural Health Monitoringapplied 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
Simulation
SensorFabrication
SensorEmbedding
SensorInterrogation
SensorEvolution
Structural Health Monitoringapplied to Marine Applications
8.90m
9.25m
15.25m
17.75m
1.10m
0.70m
0.70m
Spreader
Fibre Bragg gratings
Location of the future housing connectors
Shrouds
Front view: Schematic representation
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
Location of the future housing connectors
Fibre n°1
Fibre n°2Fibre n°3
Fibre n°4
Fibre n°5
Fibre n°7
Fibre n°6
Fibre n°8Fibre n°9
190 mm
35
0 m
m
Shape of the mast base
Base of the mast
Fibres n°1, 4 and 7
Fibres n°3, 6 and 9
Fibres n°2, 5 and 8
Preliminary tests
Naked mast
Preliminary tests
Fibre maintained on themast with tape
Preliminary tests
FBGs are glued on the mastwith 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
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, 3, 4, 6, 7 and 9 are very small
� The FBGs of the fibres n° 2, 5 and 8 are under compression
y=-3E-10x4+1E-06x3-0.0012x2-0.078x-19.343
R²=0.92681
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Bra
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Position(cm)
Preliminary tests
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
Mast is let free and is only maintained at both extremities but turned on its side
Preliminary tests
-600
-400
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1 3 5 7
Bra
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N°oftheFBG
Fibre n°4 Fibre n°6
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.
2nd phase: Embedding
- Realisation of smallgrooves- Optical fibers embedding- Filling of the grooves and protection of the sensorswith epoxy glue
2nd phase: Embedding
Ingress/egressof the optical fibers
Splicing of the optical fibers
MPO (Multi-fiber Push-On) connectorbetween the mast and the interrogator
Rapid prototyping of a waterproof housing for the connection. This one will be attached to the mast
2nd phase: Embedding
Interrogator set-up
…
e-LED
Photodiode &
Data processing
Tunable filter
Optical circulator
FBG 1 FBG x
FBG 1 FBG x
FBG 1 FBG x
Light, small size, low power consuming
Interrogator set-up
Light, small size, low power consuming
SBO Self sensing composites
Structural health
monitoring
Production monitoring
� 2 optical fibers, 10 sensors
� Designed and manufactured by
and
12/5/2013 39
Case: control arm
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