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Structural Health Monitoring of composite Plates with Piezoelectric WaferActive Sensors

Soltani, Zahra | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43274 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Abedian, Ali
  7. Abstract:
  8. Cost-effective and reliable damage detection is critical for utilization of composite materials. This research investigates a wavelet-based approach for SHM and detection of through-thickness crack in different lengths and angles in [0/45/-45/90]s CF/EP composite plate utilizing ANSYS finite element method (FEM) software and digital signal processing technique utilizing MATLAB software. To this end, a dual-PZT actuation scheme is applied, aimed at generating the S0 mode at a square composite plate. This study contributes to the damage detection by developing an improved wavelet-based signal processing technique that enhances the visibility and interpretation of the Lamb wave signals related to defects. Based on the amount of energy dissipated by the damage, a damage index is defined as the function of an electric signal’s attenuation for a limited time span and at the input frequency of the signal. It was observed that, the value of DI increases when crack length increases. Also, the effect of crack orientation on Lamb wave propagation was evaluated. Under oblique wave incidence with the current specimen and sensor configuration, it was found that, with increase of angle the value of DI increases at first and then decreases. In both of these study, when the projection the crack length in the direction of normal to the connecting line between the sensor and actuators is smaller than anapproximate thresholdvalue of 5 mm, DI has a negative value. Such undulation is attributable to the superposition of the strong scattered waves from the crack tips that travel small paths and the transmitted wave signals traveling across the crack.
  9. Keywords:
  10. Structural Health Monitoring ; Wavelet Transform ; Piezoelectric Wafer Active Sensor ; Lamb Wave ; Composite Plates

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