Static mechanical characteristics of tin-coated fiber Bragg grating sensors

• The quantity of residual strains of metal-coated FBG sensors depends on the mechanical properties of the metal coating.
• Metal-coated FBG sensors were fabricated by molten tin through a dipping method.
• Cyclic loading tests for FBG sensors were performed to explore their capability of producing permanent residual strains.
• The tensile strength of tin-coated FBG sensors was investigated by tensile tests right after the cyclic loading tests.
• The results of mechanical property tests can be used as guidelines for the installation of tin-coated FBG sensors.

Tin-coated FBG sensors, which can be used to evaluate the maximum strain experienced by host structures through the quantity of residual strain induced by the tin coating, were fabricated by a dipping method. The residual strain development of the tin-coated FBG sensors was quantitatively investigated by performing increased cyclic loading tests, and compared to that of bare FBG sensors. It was found that the quantity of residual strain showed a quadratic relationship with respect to the maximum strain experienced by the tin-coated FBG sensors, while the quantity of residual strain of bare FBG sensors was negligible. Moreover, after increased cyclic loading tests, the tensile failure strength of the tin-coated FBG sensors was additionally examined using Weibull failure statistics and compared to that of bare FBG sensors. The median failure strength of the tin-coated FBG sensors was 111.8% greater than that of the bare FBG sensors, and the Weibull moduli of the bare FBG sensors and the tin-coated FBG sensors were 13.5 and 8.1, respectively. The static mechanical characteristics of the tin-coated FBG sensors, i.e., residual strain development and the failure strength, can be used as a basis and guidelines for the installation of tin-coated FBG sensors into structures in actual applications.