Strain Transfer Analysis Of A Four-Layer Embedded Fiber Optic Sensing Model In An Elastic State

Optical fiber grating strain sensors are currently utilized in a variety of structural health monitoring applications. The encapsulated fiber optic sensor is unable to completely detect the strain of the structure, so the strain transfer theory should be established to maximize the strain sensing of fiber. It is required to explore the embedded four-layer fiber optic sensing model to create a more plausible strain transfer error hypothesis. Based on the three-layer fiber optic sensing model, the Goodman assumption and Fourier series approach were presented to study the strain transfer efficiency of the four-layer model in the elastic state. First, the physical quantity to be analyzed is determined, and finally the radius, interlayer bonding coefficient and elastic modulus are selected as the parameters affecting the strain transfer efficiency. The length range of efficiency evaluation is 0–2.5m, and the transfer efficiency under different radii is above 0.90 when the length L≥2.2m. The interlayer bonding coefficient kf between 1×1010N/m3 and 2×1011N/m3 has little impact on the transfer efficiency, and the same is true for ka, so it cannot be considered in practice. When kp is between 2.5×1010N/m3 and 1×1011N/m3 and the length L>2m, the strain transfer coefficient reaches 95%. The influence of elastic modulus on the transfer efficiency is very significant when L≤0.4m. The four-layer model performs similarly to the three-layer model within the paste length range of 1.0m, but has a superior strain transfer effect when the pasted length exceeds 1.0m. As the radius of the protective layer rises, the effect of strain transfer deteriorates.