Measurement of the local water content of an epoxy adhesive by fiber optic sensor based on Fresnel reflection

Abstract This article presents an application of a fiber optic sensor based on Fresnel reflection for the measurement of local water content within an epoxy adhesive immersed in water. The water content is directly calculated from the measured refractive index with the help of a Maxwell-Garnett model which consider spherical water inclusions inside an epoxy matrix. No calibration is needed. Three samples were equipped with fiber optic sensors and immersed in water. The measured water content was compared with a finite element simulation. The remarkable agreement between both validates the proposed method. In an industrial setting, this experimental approach could be used to monitor the aging of an immersed polymer material, bonded joint or composite structure.