Determination of dynamic strain profile and delamination detection of composite structures using embedded multiplexed fibre-optic sensors

This paper studies the dynamic strain measurement and delamination detection of clamped-clamped composite structures using embedded multiplexed Fibre-optic Bragg grating (FBG) sensors through experimental and theoretical approaches. A dynamic strain calibration of the FBG sensors and surface mounted strain gauges to find out the correlation between the strain and photovoltage is reported. The embedded FBG sensors were used to measure the natural frequency and dynamic strain of intact and delaminated composite structures. The strain profile of these structures subjected to external excitations was evaluated by using experimental measured data and a modified vibration theory. The results revealed that the use of the embedded FBG sensors is able to actually measure the dynamic strain and identify the existence of delamination of the structures. This allows the continuous estimation of fatigue life and minimises the need of in-site inspection of the structures.