Full-Spectral Measurements of Fiber Bragg Grating Sensors Embedded in Composites for Damage Monitoring

摘要

Recently, the measurement of response spectra from fiber Bragg grating (FBG)rnsensors has been shown to enable detailed visualization of the local strain orrntemperature profiles at the sub-millimeter scale through induced distortion in the FBGrnspectrum. This measurement of spectral distortion is particularly critical andrninformative when the FBG is embedded in a laminated composite material system.rnThe complex microstructure of reinforced composites creates complex, multicomponentrnstress states, particularly near damaged regions. While this complexrnspectrum provides detailed sensing information on stress states and damagernprogression within the structure, this information cannot be obtained without fullspectralrnscanning of the FBG sensor spectrum. Spectral measurements were performedrnwith FBG sensors embedded in woven carbon-fiber epoxy laminates, subjected tornrepeated low-velocity impacts. Highly distorted FBG spectra were observed due torntransverse compressive loading on the gauge during impact as well as the presence ofrnstrain fields with high gradients as delamination progressed through the laminate.rnFurther static and dynamic loading measurements are presented to highlight thernbenefits of embedded sensors for structural health monitoring applications.