Use of Fiber Bragg grating sensors in structural health monitoring

Abstract

Glass Fiber Reinforced Plastics are used in various high fatigue and high loading engineering applications due to the mechanical advantages they provide over conventional isotropic materials. Application within these environments can lead to the degradation of mechanical properties and the formation of defects within the structure. Continuous health monitoring is therefore required to approve the operational integrity of these structures, and prevent the occurrence of irreparable damages and catastrophic failure. Until recent years, Non Destructive Testing methods have been used to monitor the structural health of composite components; however these methods cause disruptions to daily operations and are costly. Recent advances in Structural Health Monitoring to include the integration of Fiber Bragg Grating Sensors in the fabrication of GFRP Composite Components have allowed for real-time measurements to be acquired through reflected FBG spectral data. Therefore to monitor the response of the a GFRP components under tensile loading and 4-point bending, two Fiber 1539nm FBG sensors operating in the infrared region, were embedded during the fabrication of a 0/90ᵒ Biaxial/0ᵒ Uniaxial Continuous Fibrous-Matrix Panel configuration purposely made with two defects. The measured response of the reflected FBG data were compared to data obtained from a FE Analysis of the Panel under equivalent loading conditions as well as data obtained from theoretical calculations. Patterns in spectral data observed during the static testing of the panel were consistent with that obtained in published works under similar conditions. Some discrepancies, however, did arise when contrasting tensile data and were thought to be due to assumptions made in theoretical calculations. Residual stresses and stress intensity factors were also considered. Inconsistencies were also found when contrasting flexural data but were attributed to the placement of the sensors within the test configuration. Recommendations to conduct future work utilising a larger configuration with multiple sensors and different defects were made. As was the recommendation to analyse the mechanical properties that a larger simulated defect has within a configuration