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Vibration Based Health Monitoring for Damage Detection of Composite Laminates

Ghaffari, Hamid Reza | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 39602 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Zabihollah, Abolghasem
  7. Abstract:
  8. Development of composite materials is one of the boldest technological advances of the last half of the twentieth century. This is due to their specific characteristics mostly considerably high strength-to-weight ratio, compared to metals and their highly customizing properties for different applications which make them a suitable material to be used in variety of domain from aerospace and automobiles to medical and sport equipments. Multi-stable asymmetrical laminates and non-uniform thickness laminated composite beams are being used as structural elements in a wide range of advanced engineering applications. Multi-stable asymmetrical laminates can be snapped between two or more geometries and have more than one stable configuration or shape. Because of the resources available in the aerospace industry these structures applications are currently under study. Non-uniform thickness laminated beams are being used as primary structural elements as turbine blades, helicopter blades and yokes, robot arms, car chassis and satellite antennas. Due to the importance of both of these primary structures, it is inevitable being assured about the healthy and safety of them for safety of the whole structure. Any small damage or crack in composite structures due to operational hazards can progress rapidly without any visible external signs. Therefore, early detection of damage in these systems during their service life is receiving increasing attention. The occurrence of damage in a structure produces changes in its global dynamic characteristics such as its natural frequencies, mode shapes, frequency response functions, etc. Vibration-based damage detection and quantification is a new category of Structural Health Monitoring (SHM) techniques. They are pattern recognition problems since they suggest the discrimination between two or more signal categories, i.e. signals coming from an intact structure and those from a damaged structure. This perspective is used in the present study for unsymmetrical laminated composite plates and non-uniform thickness laminated composite beams based on the changes in the vibration responses of the structures. The vibration responses of composite structures have studied according to an efficient and accurate finite element model (FEM) based on layer-wise theory in this study
  9. Keywords:
  10. Dynamic Response ; Layerwise Theory ; Damage Detection ; Multi Stable Asymmetrical Laminated Composite ; Non-Uniform Thickness Laminated Composites

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