Damage assessment in advanced composite structures using embedded fibre Bragg grating sensors

Three methodologies for damage assessment in glass fibre reinforced composite structures using embedded fibre Bragg grating (FBG) sensors are introduced in this paper. These are static strain, vibration-based and ultrasonic wave approaches. For the static strain method, the embedded FBG sensors are used to investigate the response of the reflection spectrum from the sensors due to delamination. Composite beams with various delamination locations along their thickness-wise direction are studied. Quantitative damage detection is demonstrated by using the FBG sensors to measure the change of vibration characteristics of composite beams. The correlation of the vibration characteristics and the corresponding delamination size and location is established by a theoretical model. Both delamination size and location can be identified based on the change of the vibration characteristics with genetic algorithm (GA), simultaneously. The ultrasonic wave sensing ability of embedded and surface bonded FBG sensors in the beams is compared. Verification of using the embedded FBG sensors for ultrasonic damage detection was conducted experimentally. Potential applications on the use of the FBG sensors for damage detection in real-life engineering structures are discussed