Quantitative identification of delamination at different interfaces using guided wave signals in composite laminates

Abstract

This article presents the development of a quantitative method for identifying interfacial delamination in composite laminates. Splitting and merging occur as Lamb waves pass through the delamination. It is demonstrated from the dispersion curve of Lamb waves that the group velocities of A 0 and S 0 modes in the sub-laminates above and below the delamination area are different when the delamination interface is not at the thickness center of a symmetrical layup laminate. Changes in the time of flight (ToF) of A 0 and S 0 modes are caused by the parallel propagation of Lamb waves. Based on those changes in the ToF, delamination size can be evaluated even though the delamination location through the thickness is not pregiven. Numerical and experimental studies are conducted to assess this method. Continuous wavelet transform is applied to extract the ToF of A 0 mode waves from the overlapped signals. Mode conversion is illustrated for the interaction of Lamb waves and delamination. The sensitivity and applicability of the proposed method are validated numerically and experimentally in two asymmetric layup composite laminates. The limitation of this method for symmetric layup composite laminates is analyzed and a potential improvement approach is further discussed.

PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization

“…Piezoelectric thin films have been used vastly as sensors, accelerometers, micro-motors, and many other low-force electromechanical (E/M) applications [1]. However, high-frequency transducers for structural health monitoring and vibration control systems usually require higher thicknesses to convey E/M stimulation loads appropriately [2,3,4,5,6,7,8,9]. Therefore, thin films cannot be applied this way.…”

Wave Propagation in Aluminum Honeycomb Plate and Debonding Detection Using Scanning Laser Vibrometer

“…Because of the mode-tuning affection of PZT, the energy distribution in different mods changed according to varying frequencies. The quasi- mode was most pronounced at a low-frequency band, while the quasi- mode was more dominant at higher frequencies [ 29 ]. Although the quasi- S 0 mode was the dominant mode at high frequencies, its out-of-plane vibration was minimal.…”

“…In the transient analysis, a small element size was enforced on the finite element model to accurately capture the GWs propagating in the HSS. The element size needed to be small enough to guarantee that there were at least ten elements per wavelength along the wave propagation direction [ 21 , 29 ]. Moreover, the integration time step needed to be small enough to ensure stability of the transient analysis [ 15 ].…”

Active Vibration Control of a Piezo-Bonded Laminated Composite in the Presence of Sensor Partial Debonding and Structural Delaminations

“…Some contemporary engineering applications of the smart composite laminates are in the aerospace, automotive, marine, and robotics fields [1,2,3], among others Although smart composite laminates offer the advantages of self-sensing [4], diagnostics [5], vibration and noise suppression [6,7], shape control [8], and can respond to changing environments [9], they are also susceptible to various types of damage in the orthotropic host laminates as well as partial debonding failure of the smart elements [10]. Some frequent damages in laminated composites are delamination [11,12], matrix crack [13,14], fiber breakage [15], among others. Delamination is one of the most feared and major modes of failure, because of its serious implications for the integrity of the structure [16].…”