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Investigation of Damage in Composite Structures under Vibration Using Hilbert-Huang Transform

In this study, the behavior of damaged and undamaged composite structures under dynamic loading is investigated by using Fast Fourier transform (FFT) and Hilbert-Huang transform (HHT) techniques. Unidirectional composite beams with and without damage were tested in vibration in a clamped-free configuration. The damage was introduced by inserting release film of two different diameters at the midplane of the beams. Strain distributions from within the beams were obtained from optical fibers embedded one ply below the surface. The beams were also instrumented with surface-mounted dual-axis accelerometers. The beams were subjected to a frequency sweep of 1-50 Hz with the oscillations induced by a shaker unit. The vibration response using FFT and HHT of the damaged and undamaged composite beams using optical fiber sensors and accelerometers data is presented.