Fatigue Resistance of a BFRP-Encapsulated Long-Gauge FBG Strain Sensor under Cyclic Train Loads

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Fatigue Resistance of a BFRP-Encapsulated Long-Gauge FBG Strain Sensor under Cyclic Train Loads

Wu, Bitao / Zhou, Yujian / Lu, Huaxi / Huang, Yun / Zhou, Zhenwei

To verify the performance of a basalt fiber reinforced polymer (BFRP) fiber-encapsulated long-gauge strain sensor in railway bridge health monitoring, this paper studies the fatigue resistance and durability of the BFRP fiber-encapsulated FBG sensor under train loads. First, the influences of the length of the anchorage section and the length ratio of the sensing section on the accuracy of the sensor were studied. Then, the BFRP sensor was applied to a sleeper for 2 million cycles of tension fatigue testing. The strain-time history of the whole fatigue test was monitored and compared. After the test, a calibration test was carried out to verify the accuracy and repeatability of the sensor. Finally, the slip and fatigue cracking of the fiber in the anchorage section of the sensor were observed by electron microscopy. The results show that the gap between the anchoring section and the bare optical fiber was filled with epoxy resin, and there was no slip behavior. No fatigue cracking occurred in the fiber, and the strain coefficient and linearity of the sensor showed no obvious changes after 2 million cycles of loading. The long-gauge strain sensor encapsulated by BFRP fibers exhibited good fatigue resistance and can meet long-term monitoring requirements under train loads.