Detection of Debonding in Adhesively Bonded Al-GFRP Joints with Embedded EFPI Fiber Optic Sensors
Katsuhiko OSAKA, Tatsuro KOSAKA and Yoshihiro SAWADA
Abstract:In the present study, a monitoring technique has been investigated in which debonding of adhesive composite joints is detected using Extrinsic Fabry-Perot Interferometric (EFPI) optical fiber sensors embedded in the adherend. First, strains at the end of the bonded part in adhesively bonded aluminum-GFRP single lap joints were measured using the monitoring system with an EFPI sensor constructed in our laboratory. The initiation and development of the debonding was also observed by eyes in the experiment. Strain analysis was performed for the joint specimens by FEM. These results showed that the strain monitoring system had the ability to measure the change in strains caused by the initiation and development of the debonding at the bonded part. Secondly, the strain monitoring using two EFPI sensors having the different gage length was performed for the same aluminum-GFRP joint specimens. The tensile loading experiments and strain analysis were performed by almost the same procedure as those using one EFPI sensor. These result showed that two EFPI sensors could measure the high and low mean strain at the bonded area corresponding to their gage lengths and detect the change in strain distributions caused by the occurrence and development of the debonding. Therefore, it was found that this monitoring system had the detection ability of the debonding in the adhesively bonded FRP joints. Key Words:Optical fiber sensor, EFPI, Adhesively bonded joint, Debonding, Health monitoring, GFRP