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Developing Classical and Nonlocal Interlayer Shear Models for Free Vibration Analysis of Multilayer Graphene Plates

Nikfar, Mohsen | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53663 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Asghari, Mohsen
  7. Abstract:
  8. Experimental observations on multilayer graphene structures show that interlayer interactions including compressive and shear effects between layers are very important in their mechanical behavior. Existing analytical investigations have generally addressed the issue of pressure interactions between layers using interatomic potentials, while the models which consider the interlayer shear effect are rarely found in the literature. To address this shortcoming, this thesis presents a new formulation for multilayer graphene structures with desired shapes and boundaries, taking into account the interlayer shear effect according to the classical continuum mechanics theory. Next, size-dependent models are developed for rectangular multilayer graphene sheets based on nonlocal continuum mechanics theory. Then, molecular dynamics simulations and numerous parametric studies are presented to validate and evaluate the proposed models as well as to study the mechanical behavior of multilayer graphene sheets. Comparison of the results shows that the responses obtained from the presented models which consider the interlayer shear and nonlocality effects are in good agreement with the results of the molecular dynamics simulations. Findings of this thesis show that considering the interlayer shear effect increases the frequency corresponding to the simple mode shapes up to 77% for the classical theory and in the case of simply support boundary conditions. Also, considering the same effect reduces the frequency of complex modes up to 60% for the nonlocal theory and same boundary conditions. The results obtained from the model containing both the interlayer shear and nonlocal effects reduce the pull-in voltage by 31% and increase it by 28% for the clamped and cantilever boundary conditions, respectively. Therefore, it is necessary to consider the above two effects in the design and analysis of multilayer graphene sheets used in nanoelectromechanical systems
  9. Keywords:
  10. Nanoelectromechanical Syestem (NEMS) ; Pull-in Phenomenon ; Nonlocal Continuum Theory ; Continuum Mechanics ; Interlayer Shear Strength ; Multilayer Graphene Structure ; Free Vibration

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