The detection of fatigue-induced damage within fibre-reinforced composite materials is of vital importance in areas where these materials are used for critical load-bearing applications. Embedded fibre-optic sensors are suitable for damage detection in composite materials because they can be easily integrated into the structure with minimal interference with the bulk properties of the composite. In this current study, a novel intensity-based optical fibre sensor was designed and evaluated under tension/tension and tension/compression fatigue loading conditions. This intensity sensor has the ability to monitor rapid strain changes without loss of the reference level. Furthermore, this sensor utilizes relatively simple and inexpensive instrumentation. The fibre-optic strain sensor was embedded within a 16-ply 0/90 carbon/epoxy laminate at the manufacturing stage. The embedded optical fibre sensor was not found to affect the fatigue life of the composite both under tension/tension and tension/compression loading. The feasibility of using the embedded sensor for fatigue damage detection was demonstrated. Excellent correlation was also obtained between the strain data from a surface mounted optical fibre sensor and a surface-mounted extensometer under fatigue loading conditions.
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