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Exploring Auxetic Metamaterials by Changing the Geometrical Parameters

Ashouri, Amir | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50182 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Naghdabadi, Reza
  7. Abstract:
  8. The properties of metamaterials can be tailored through modification of their microstructures geometry. In this regard, a vast range of metamaterials have been designed. Auxetic metamaterials are a novel class of materials exhibiting the interesting characteristic of negative Poisson’s ratio. Theoretically, auxetic metamaterials have improved mechanical properties such as shear modulus and fracture toughness. The design and modeling of auxetic metamaterials is not completed yet. In order to exploit the interesting properties of auxetic metamaterials, their potential applications have been investigated in medical, sports, automobile and defense industries, so far. In the present work, the history of auxetic metamaterials has been reviewed. Then, after describing the mechanisms leading to the negative Poisson's ratio, a new microstructure for auxetic metamaterial is proposed. Using theoretical analysis and numerical simulations, the in-plane mechanical properties for the proposed metamaterial, including Young’s modulus and Poisson’s ratio have been determined. Taguchi method has been used to study the maximum variation of Poisson's ratio and Young's modulus for the metamaterial. To validate the results, Poisson's ratio and Young's modulus for the metamaterial have been compared with the corresponding values in the literature, for the specific case. Since the metamaterial has been investigated in a two-dimensional mode under uniaxial compression, the buckling of the microstructure members is possible. Thus, the critical buckling load of the metamaterial has been calculated analytically. The results confirm negative Poisson’s ratio for the metamaterial. Also, there is a good agreement between the numerical and analytical results. The maximum and minimum values of Poisson’s ratio for the proposed metamaterial are -6.4 and +4.2, respectively; while the Poisson’s ratio for metamaterial with the honeycomb microstructure, the customly used auxetic microstructure, is varied between -5 and 0. The maximum Yang's modulus obtained for the proposed metamaterial is 5.1 GPa, which is approximately five times more than that of the metamaterial with honeycomb microstructure
  9. Keywords:
  10. Metamaterial ; Elastic Properties ; Taguchi Method ; Mechanical Properties ; Auxetic Materials ; Negative Poisson's Ratio

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