1. The Engineering Integrity Society
Presentation to:
The Engineering Integrity Society
4th Durability & Advances in Wind, Wave and Tidal Energy Conference 28 January 2016
Rob Knapp

2. Fibre-optic sensing for high performance structures
Epsilon Optics Ltd
Epsilon Optics Aerospace Ltd
Directors
Rob Knapp
Roger Caesley
Principal markets
Civil Engineering
Marine (high performance yachts)
Aerospace and Defence
Tidal Energy
Fibre-optic sensing for high performance structures
Specialising in the application of fibre-optic sensing

3. Why monitor strain? Design verification and improvement
Confirmation of load cases
Impact detection
Long term structural health monitoring
In service load measurement
Real time performance improvement
IPC – reducing fatigue loads
Fibre-optic sensing for critical structures
Specialising in the application of fibre-optic sensing

4. Why Fibre-optic Sensors?
Advantages
Many sensors can be multiplexed on a single optical fibre
Resilience to chemical attack and salt water immersion
Excellent fatigue performance
Not subject to Poisson’s Ratio effects
Long-term accuracy and stability
Can be embedded in composite structures
Immunity to electro-magnetic interference
Suitable for hazardous environments
Able to locate readout instrumentation remote to sensor due to low transmission loss of fibre
Fibre-optic sensing for critical structures

5. Fibre Bragg Grating Sensors
FBG sensors consist of :
Core, 9 microns, silica glass
Cladding, 125 microns silica glass
Buffer, 250 microns, acrylate, polyimide..etc.
Specialising in the application of fibre-optic sensing

6. Fibre-optic sensing for critical structures
Interrogators
Wave Division Multiplexing
Time Domain Multiplexing
Fibre-optic sensing for critical structures

7. Fibre-optic Sensor Interrogation units
OEM1000 series
1, 2, and 3 Channel units with 500Hz scan speed and up to 100 sensors
4 Channel switched unit, 2Hz scan speed and up to 100 sensors per channel
More than 2000 units in service to date.
EA-3080-H-E
EA-3030-H-422
8 channels – high speed solid state optical switch
Up to 10kHz
Compact and rugged design
100 sensors per channel
1 to 4 channels
Up to 10kHz
Compact and rugged design
Tested to aerospace specification DO160F
Specialising in the application of fibre-optic sensing
Fibre-optic sensing for high performance structures

8. Examples (1) Fibre Optics compared with Strain Gauges
Fibre-optic sensing for critical structures
Specialising in the application of fibre-optic sensing

9. Fibre-optic sensing for critical structures
Sensor deployment
Important considerations
High strain gradients
Operating temperature
Two common deployment methods
Embedded – the optical fibre is within the composite structure
Surface bonded – this is suitable for both composites and metallic structures.
Fibre-optic sensing for critical structures

10. Fibre-optic sensing for critical structures
Embedded Sensors
Issues
Fibre seen as inclusion – Reduction in overall strength including fatigue
No evidence to support this is fibre correctly embedded
Micro Bending – Causes excessive optical loss
Correct selection of optical fibre particularly
coating type
Protection of fibre within UD plies or tow
Ingress/egress point – Point most vulnerable to damage
Correctly engineered – use of special connectors etc
Repairability
Embedded sensors are not repairable
BUT if fail are evidence of serious damage to the component
Fibre-optic sensing for critical structures

11. Embedded Sensor - Advantages
There for the life of the component
Robust (failure indicates that structure has suffered serious damage)
Can monitor strains at depth within the component
Can be used to monitor temperature during cure
Fibre-optic sensing for critical structures

12. Fibre-optic sensing for critical structures
Surface Bonded Sensor
Optical fibre normally mounted within a composite patch to provide protection and ease handling.
Advantages:
Patches are easy to bond on
Can be shaped to conform with the structure further simplifying installation.
Easily integrated into production process
Can be used on both metallic and composite surfaces
Fibre-optic sensing for critical structures

13. Typical sensor patch installation
Fibre-optic sensing for high performance structures
Specialising in the application of fibre-optic sensing

14. Tidal Stream Energy Generation
Applications
Tidal Stream Energy Generation
Fibre-optic sensing for high performance structures

15. Tidal Stream Energy Generation
Applications
Tidal Stream Energy Generation
Fibre-optic sensing for high performance structures

16. Applications Tidal Stream Energy Generation
Single channel sub-sea connector
Sub-sea expanded beam connector integrated into a sensor patch for deployment to 6000m depth
Fibre-optic sensing for critical structures
Specialising in the application of fibre-optic sensing

17. Tidal Stream Energy Generation
Applications
Tidal Stream Energy Generation
Fibre-optic sensing for high performance structures

18. Applications Tidal Stream Energy Generation
Fibre-optic sensing for critical structures
Specialising in the application of fibre-optic sensing

19. Tidal Stream Energy Generation
Applications
Tidal Stream Energy Generation
Fibre-optic sensing for critical structures
Specialising in the application of fibre-optic sensing

20. Fibre-optic sensing for critical structures
Conclusion
Fibre-optic sensing technology is particularly well suited to the monitoring of tidal energy turbines, and other sub-sea structures.
Provide the system is well engineered and installed it is capable of providing high reliability and accuracy for the full service life of the turbine.
Installed cost is relatively low
Installation is usually easily integrated with other production activities
Fibre-optic sensing for critical structures

21. The Engineering Integrity Society
Presentation to:
The Engineering Integrity Society
4th Durability & Advances in Wind, Wave and Tidal Energy Conference 28 January 2016
Rob Knapp