Application study on fiber Bragg grating sensors in damage monitoring of sandwich composite joints

Abstract

This article studies the application of fiber Bragg grating sensors in damage monitoring of sandwich composite L-joints, which aims to reveal the interface damage between the GFRP skin and the foam core. Fiber Bragg grating sensors have been arranged based on numerical results. The ultimate load and failure location via numerical modelling have been experimentally verified. Strains measured by fiber Bragg grating sensors have shown anomalies with load increased, indicating the onset and propagation of damage. Based on the damage-induced strain anomalies, four stages have been addressed to reveal the emergence, accumulation and propagation of damage during the loading process. Measurements by numerical simulation and surface mounted strain gauges have been found to be less sensitive to internal damage, proving the great significance of embedding fiber Bragg grating sensors to monitor interface damages of sandwich L-joint.

Adhesive Joint Integrity Monitoring Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…Instead of directly looking for defects, there are relatively more economical techniques suitable for real-time monitoring of the integrity degradation of adhesive joints. These include strain/stiffness monitoring using back face strain gages [21][22][23], resistance monitoring of adhesive joints made conductive by adding carbon nanotubes [24,25] and optical fiber sensors signal surveillance [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Strain gages can only be applied to the outer surface, but they will disrupt an otherwise smooth surface and are susceptible to environmental degradation.…”

“…There are different kinds of optical fiber sensors. In adhesive joints, both the distributed sensing [29][30][31] and the discrete fiber Bragg grating (FBG) sensors have been used [8,[32][33][34][35][36][37][38][39][40][41][42][43]. The distributed sensors provide a spatially continuous strain measurement along the whole fiber and can reveal the location of any perturbation in strain caused by damages in the bond.…”

“…The distributed sensors provide a spatially continuous strain measurement along the whole fiber and can reveal the location of any perturbation in strain caused by damages in the bond. With the discrete single peak FBG sensors, the peak wavelengths were often logged and converted to strain [32][33][34][35][36][37][38]. In this way they behave as strain gages but have advantages such as embeddability, multiple sensors on the same fiber and immunity from electromagnetic interference.…”

Hygrothermal Damage Monitoring of Composite Adhesive Joint Using the Full Spectral Response of Fiber Bragg Grating Sensors

“…Instead of monitoring moisture content or directly looking for defects, there are techniques suitable for real time monitoring of the integrity degradation of adhesive joints. These include strain/stiffness monitoring using back face strain gages [ 49 , 50 , 51 ], resistance monitoring of adhesive joints that were made conductive by adding carbon nanotubes [ 52 , 53 ] and optical fiber sensors signal surveillance [ 43 , 44 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. Strain gages can only be applied to the outer surface, they will disrupt an otherwise smooth surface and are susceptible to environmental degradation.…”

Monitoring of dimple formation in honeycomb sandwich structures using distributed fiber optic sensors

“…Fiber optic strain measurement systems seem promising [13–15] and have been successfully applied to monitor sandwich structures [16–20] and to predict the deformation shape of structures [21,22]. In previous studies [12,23,24], fiber Bragg grating (FBG) sensors have been applied on the face sheets to detect dimpling.…”