Delamination detection with fibre Bragg gratings based on dynamic behaviour

The influence of a delamination on the resonance frequencies of laminated composite beam is investigated. A model, proposed by Mujumdar and Suryanarayan [Mujumdar PM, Suryanarayan S. Flexural vibrations of beams with delamination. J Sound Vib 1988;125(3):441–61], of the dynamic properties of delaminated isotropic beams is extended to anisotropic laminated beams. Parameter studies show that the resonance frequencies are a function of both delamination parameters (location and size) and laminate lay-up. Experimental and analytical resonance frequencies for undamaged and delaminated test samples show good agreement. The resonance frequencies of carbon-PEI laminated cantilever beams were measured using embedded fibre Bragg grating strain sensors. High frequency measurements were performed by using a slope-filter based interrogator.