Abstract: The detection of fatigue damage within composite materials is vital for the safe use of these materials in engineering structures. Embedded fiber-optic sensors have been identified as suitable for damage detection in these materials, as they have minimal interference with bulk composite properties. The relationship between fatigue damage within a composite material and the associated moduli changes have been used to characterize damage development and progression. An intensity based fiber-optic strain sensor has been designed and evaluated for damage detection in composite laminates. This intensity sensor has the ability to monitor rapid strain changes without loss of the reference level. This sensor utilizes relatively simple and inexpensive instrumentation. In this study the fiber-optic strain sensor has been embedded within a 16 layer cross-ply carbon/epoxy laminate. The response of the sensor has been compared to that obtained from strain gauges and an extensometer. The composite coupons with the embedded sensors have also been subjected to tension-tension and tension- compression fatigue. The stiffness decay of the composite during fatigue loading was monitored in real-time.!34
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