technology

Load Measurement System Requirements for SHM Applications

• Accurate, reliable load sensor input over the airframes life
• Real time measurement of strain
• Ability to cover all critical areas of the structure
• Simple, low cost methods of integrating the sensors into the structure
• Reliable, cost effective interrogation of the sensors
• Compatibility with aircraft data handling systems and ability to interface with other Health Monitoring Systems

Key Benefits of Insensys Strain Measurement System

• Robust fully solid state interrogator with proven reliability which is in series production
• Built in computational power to facilitate integration with various data bus protocols
• Can be simply integrated into a larger HUMS LRU
• Light weight (approximately 500 grams depending on installation)
• Low power requirement (3 watts)
• Ability to interrogate over 100 sensors on a single fibre
• Full 9000 microstrain on all sensors
• Fully resistant to EMI and EMP
• Flexible interrogation frequencies for individual sensors with alarms to triggers to adjust sample rate
  
• Identical sensors that can be written without the need to remove the optical fibres protective coating giving a more robust fibre that is easier to produce
• Extensive fatigue tests to underpin installed life of Insensys optical fibre tests have exceeded 18 million cycles.

Methods Sensor Installation

• Composite patch techniques to facilitate monitoring of both metallic and composite structures (developed in conjunction with Airbus UK)
• Connector systems, both edge and surface, to overcome the need for vulnerable "flying leads" (suitable for both vacuum bag and closed mould (RTM) manufacturing processes)
• Optical fibre protection systems (fibre carried in pre-impregnated carbon or glass fibre TOW and proven in use in automatic tape laying machines developed in collaboration with Hexcel Ltd)

Future Developments

Acoustic sensors for damage detection (Collaborative programme with QinetiQ plc to combine existing optical fibre strain measurement systems with fibre laser sensors to measure acoustic frequencies between 1 and 100 kHz for defect detection and location, demonstration system by end 2007).

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