Strain sensor based on fiber bragg grating bonded with graphene on polymer plate

Abstract

Fiber Bragg Grating (FBG) sensing has been intensively studied in the application of smart structures because of its immense advantages offered over those of the conventional sensors. In this study, the sensing characteristics of FBG bonded onto graphene and polymer plate are demonstrated under various mechanical deflections within the tension and compression modes. The sensing elements utilized for this purpose were 5 mm, 15 mm, 25 mm, and 35 mm FBG sensor bonded onto the surface of graphene with polymer plate. To accomplish these tasks, the lateral displacement was changed stepwise at different stress locations of 1 cm, 2 cm, and 3 cm applied away from the movable end of the FBGs, by which the curvature of the graphene with polymer plate is changed. An almost linear relationship between the sensitivity and deflection was observed for the FBGs bonded onto polymer plate and deflected at stress locations of 1 cm and 2 cm. However for the stress location of 3 cm it was deviated from being linear. Meanwhile FBGs bonded with graphene on polymer plate, the relation curves were also deviated from being linear. The sensitivity at 3 cm stress location for tension and compression modes was found to be larger than those for other applied stress locations and this is valid for both cases; graphene on polymer plate or on polymer plate only. It was also established that regarding the shift in Braggs wavelength center, both tension and compression processes are valid and comply with the physical observations. Moreover, for the FBGs bonded with grapheme on polymer plate, the sensitivity was increased upon the increment of grating length. It was also discovered that sensitivity of the FBG sensor for the small grating lengths of FBG (5 mm and 15 mm) was enhanced and it was observed that the response of compression mode is better than that of tension. However, for large grating lengths (25 mm and 35 mm), the tension mode response was found to be larger than that of compression. It was noticed that the hysteresis effect is significant in the tension mode and showed greater values in the large grating FBG. An interest linear relationship was determined between the optical and intensity (electrical) outputs.