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

Fibre-optic sensing for high performance structures Epsilon Optics Ltd. - 2007 Epsilon Optics Aerospace Ltd - 2010 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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