Comparative study of digital image correlation, a strain gauge, and an extensometer for calibration of fiber Bragg grating sensors

Subject of study. A method for calibrating temperature sensors and stress sensors based on fiber Bragg grating sensors is studied. Purpose of the work. The efficiency of various sensor calibration methods, in particular, hardware-based methods based on strain gauges with a sensitive element in the form of a metal foil, an extensometric device, and software-based methods based on the correlation of recorded digital images is compared. Method. The strain calibration experiments were conducted on metallic and laminated carbon/epoxy specimens in four monotonic tensile tests. Additionally, the temperature calibration for fiber Bragg grating sensors was carried out using a controlled oven. Main results. The digital image correlation method showed greater deviation than the other methods, which could be due to the lower sensitivity of this method to such a range of strains in this special test. The results show remarkable conformity between fiber Bragg grating sensors and strain gauge data. The strain and temperature sensitivities of 0.85 pm/µɛ and 11.9 pm/degree are obtained for the used sensors, respectively. Practical significance. Calibration of fiber Bragg grating sensors, before installing and embedding them into the structures, to temperature and strain using a reliable method has always been one of the concerns of active researchers in this field. This article has compared mechanical and optical methods in the same tests.