| Abstract [eng] |
In aerospace applications, structural health monitoring (SHM) requires enabling safety, reliability, and quality control of the structure. Among SHM techniques, ultrasonic guided wave (GW) techniques are widely used due to versatile applications. The primary advantage of the guided waves for the inspection of multi-layered structures are: these waves are sensitive to small changes in the object under inspection, can propagate long distance with less attenuation, and enables long-range inspections. Hence, guided wave inspection techniques are preferred for the application of multi-layered composite structures. It is important to note that the GW multimode and dispersive nature leads to complex signal interpretation. Therefore, the preferred mode can be selected to reduce the complexity. Although multi-mode inspections are efficient in some inspections. However, signal processing methods can be implemented to filter the guided waves to reduce the complexity. The semi-analytical finite element method was used to obtain the GW dispersion parameters and mode selection. GW signal damping in anisotropic composite structures cannot be neglected. GW attenuation calculation is a critical parameter for mode selection and long-range inspection. Therefore, it is important to estimate the signal attenuation to achieve uncompromised and reliable results. This research focuses on the GW propagation in a multi-layered CFRP panel to determine the delamination position in the longitudinal direction. The 2D and 3D finite element simulations were performed to study in detail guided wave interaction with delamination. The influence of delamination size and location was examined in the CFRP panel. The variation in delamination size and position significantly influences the transmitted and reflected GW amplitude. The key features analyzed in this research are GW mode behavior with delamination, mode velocity, time of flight (ToF), wavenumber, and wavelength. By analyzing these characteristics of the reflected and transmitted mode, the delamination presence, location, and severity can be estimated. The forward and backward scattered and converted modes are filtered to reduce the complexity of signal interpretation. The inverse 2D FFT was used to preserve the forward converted mode. |
