Structural health monitoring of marine composite structural joints using embedded fiber Bragg grating strain sensors

This paper presents a method for the health monitoring of composite joints based on strain measurements using distributed embedded fiber Bragg grating (FBG) sensors. Secondary bonded woven E-glass/vinyl ester composite doubler plate joints were subjected to fatigue tension loading to induce stable crack propagation. A finite element (FE) model was developed to correlate experimental strain measurements prior to cyclic loading with the numerical predictions and to determine the sensitivity of the sensors to changes in longitudinal strain due to crack growth. Initial quasi-static tension tests demonstrated satisfactory correlation between the strains from the FBG sensors and FE predictions. The changes in longitudinal strain distribution during the fatigue tests were correlated with crack growth. A progressive shift in the strain distribution in the vicinity of the crack was observed. The experimental results demonstrated that a strain-based methodology can be utilized to detect crack propagation in this type of composite joints.