Development of Bragg fiber sensor for corrosion detection / Tan Cai Hui

Tan , Cai Hui (2020) Development of Bragg fiber sensor for corrosion detection / Tan Cai Hui. PhD thesis, Universiti Malaya.

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Abstract

Steel corrosion has posed one of the major structural defects in the civil society today. Conventional methods for corrosion monitoring involve high maintenance cost and destructive methods with low accuracy. Recently, Fiber Bragg gratings (FBG) sensor with its high sensitivity in measuring strain and temperature have been widely studied and used in structural health monitoring (SHM). A non-destructive corrosion detection approach based on FBG sensors was developed and tested to monitor corrosion in this research work. The principle of FBG sensing is based on Bragg wavelength shifts that from the corrosion process that induced strain on the FBG due to mechanical expansion. The first method that had been carried out in this study was the Polydimethylsiloxane (PDMS) coated FBG; while second method was the development of new coating material with better sensitivity for corrosion detection, which was a mixture of PDMS strain sensitive materials and pH sensitive hydrogel. FBG were etched in hydrofluoric acid (HF) near to the core of 9.7 µm to enhance the FBG sensitivity before the application of a coating material. FBG sensors were embedded on the rebar specimen. This is to monitor the strain expansion caused by corrosion process. Their performances were then being monitored by observing the Bragg wavelength shift via FBGA. Generally, PDMS-hydrogel sensor better sensitivity for corrosion monitoring at 1.97 nm / mm / year followed by FBG-PDMS at 1.65 nm / mm / year, as compared to non-coated FBG at 1.21 nm / mm / year. Overall, this research work have revealed and proven that it is feasible to develop FBG sensors as a real-time non-destructive structural health monitoring system in civil engineering.

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