Structural Health Monitoring of Adhesively Bonded Skin-Stiffener Composite Joint Using Distributed Fibre Optic Sensor

The structural component evaluated in this research is a simplified representation of composite skin-stiffener joint found in a helicopter tail boom, which was monitored during quasi-static loading conditions using distributed fibre optic sensors, along with resistance wire strain gauges and flash thermography. The skin and the stiffeners were fabricated out of unidirectional carbon fibre prepreg (CYCOM G40-800/5276-1) from Cytec and were bonded with AF163-2K structural film adhesive from 3M. The path chosen for the fibre installation was designed to provide strain response for comparison with the strain gauges, as well as to witness any change in the strain due to disbonding between the stiffener and the skin. The component was quasi-statically loaded until the skin-stiffener joint fully disbonded. The fibre optic sensor was able to detect and track the damage growth during quasi-static testing by monitoring variations in the strain distribution at the skin and stiffener interface. Results from the fibre optic sensor corroborated well with the inspection carried out using flash thermography.