The effects of the transverse strain on the fiber gratings to the wavelength shift of the FBG (fiber Bragg grating) sensor were investigated. A new FBG model including the strain transmissibility coefficients along the longitudinal and transverse directions was proposed. The finite element method was applied to obtain the strain transmissibility coefficients of the interface between FBG sensor and base structure surface. The wavelength shift of each FBG sensor was calculated for the assumed strain condition of the base structures. Simulated core strains based on both conventional 1-DOF model and the present model were compared. The numerical results showed that the surface strains could be well predicted using the proposed FBG model while the conventional 1-DOF model gave large errors when the transverse strain of the base structure was significant as in composite structures under thermal loadings.

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