Evaluation of embedded optical fiber sensors in composites: EFPI sensor response to fatigue loading

Extrinsic Fiber Fabry-Perot Interferometric (EFPI) sensors were fabricated and embedded within a 16-layer cross-ply composite. The composites with and without the embedded EFPI sensors were subjected to tension/compression loading. The presence of the embedded sensor was not found to have adverse effect on the tension/compression fatigue properties. However, the performance of the EFPI sensor was found to degrade with fatigue cycles, with the introduction of a compressive element in the loading regime; samples were tested using stress ratios of -1, -2.5, and -3. Although the reasons for this observed degradation in the response of the sensor to applied strain is not known at present, it is speculated that this may be due to debonding of the key components of the sensor.