Analysis of the strain transfer in a new FBG sensor for Structural Health Monitoring

Structural Health Monitoring (SHM) is a topic of great interest in structural engineering due to the ageing of the built infrastructures and the growing use of innovative structural systems and construction materials. Although several sensing technologies have been developed for use in SHM systems, fiber optic sensors, especially Fiber Bragg grating sensors (FBGs), are now attracting much attention due to their advantages over other types of sensors. aper presents a new FBG strain sensor with an unsymmetrical packaging configuration designed to be fixed to the surface of the monitored structure. A 3D Finite Element numerical analysis of the sensor, packaging and adhesive used to fix the system to the host structure was conducted to study the influence of (1) the thickness and mechanical properties of the adhesive, and (2) the configuration of the packaging on the accuracy of the sensor. The results obtained from the numerical models show that the strains measured by the proposed system and the actual strains in the host structure differ by less than 2.5% due to the fact that the packaging contains only one layer of composite material in an unsymmetrical configuration. The proposed design can thus be said to be an improvement compared to the typical configurations of optical fiber surface strain sensors.