Abstract
An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain in the host structure. For a surface bonded optical fiber sensor, the measuring sensitivity is strongly dependent on the bonding characteristics which include the protective coating, adhesive layer and the bonding length. Thermal stresses can be generated due to a mismatch of thermal expansion coefficients between the optical fiber and host structure. The optical fiber thermal strain induced by the host structure is transferred via the adhesive layer and protective coating. In this investigation, an analytical expression of the thermal strain and stress in the optical fiber is presented. The theoretical predictions are validated using the finite element method. Numerical results show that the thermal strain and stress are linearly dependent on the difference in thermal expansion coefficients between the optical fiber and host structure and independent of the thermal expansion coefficients of the adhesive and coating.
Highlights
The use of optical fiber sensors in structural health monitoring has increased rapidly
Optical fiber sensors based on the fiber Bragg grating (FBG) have been demonstrated successively in monitoring structures
Mulle et al [4] used FBG sensors to measure the residual strain in carbon-epoxy composite laminates
Summary
The use of optical fiber sensors in structural health monitoring has increased rapidly. To separate the mechanical strain from the temperature effect, it is necessary to determine the thermal strain of the optical fiber sensor when the host structure is subjected to a temperature change. Mueller et al [14] proposed a high-precision thermal strain measurement model using surface bonded FBG sensors. Proposed a new FBG model to investigate the effect of transverse strain on the measurement of thermal strain in composite materials. Yoon et al [18] performed experimental test to valid this model by measuring thermal expansion of anisotropic composite specimens and an isotropic invar specimen. In this investigation, the optical fiber sensor is surface bonded onto the host structure. The theoretical prediction of the thermal strain in the surface bonded optical fiber sensor is validated using the finite element method
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