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Investigation of Mechanical Properties of Pentamode Metamaterial with Unconventional (non-diamond) Unit Cell Structure

Shafia, Moein | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58103 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Akbari, Javad; Mohammadi, Kaivan
  7. Abstract:
  8. The creation of materials with properties at the human satisfaction and beyond what is found in nature has long been the subject of various studies. One of the structures that have received a lot of attention recently is metamaterial. Metamaterials are engineered and purposefully designed materials that, due to this aspect, show unique properties that are not usually found in nature. These unique properties are mainly due to their designed microstructure, which exhibits properties beyond the base material from which they are made. The pentamod metamaterials are among these materials with uncommon properties. A pentamod metamaterial is a three-dimensional structure with a specific microstructure that makes it act like a fluid despite being solid, i.e., while it does not show shear strength in one specific direction, it does withstand pressure. To create metamaterials like natural crystals, it requires to design unit cells which with the expansion of them in three dimensions, the desired metamaterial will be created. To create the pentamod metamaterial, a conventional unit cell so-called "Diamond unit cell" will be utilized. In this type of unit cell, the struts, like the arrangement of carbon atoms in a unit of a diamond cell, will be bound together and by expansion and replication of this structure in the space, the pentamod metamaterial will come into existence. The execution of the present project aims to deploy the non-diamond metamaterial of the pentamod and extraction of its mechanical properties such as Young's modulus, shear modulus, Bulk modulus, Poisson's ratio, and yield strength. In non-diamond expansion, the way the struts are connected is different; Also, further diagrams are used as a unit cell to create the pentamod metamaterial. In the process of the expansion, among the ordinary cells, three cells including the cubic, the Truncated cube and the Truncated octahedron are considered. The method of this research can be framed this way. Firstly, by employing computer-aided design software, we design and expand the above-mentioned unit cells according to the position of the struts. Then, using the finite element method, we develop a numerical model to obtain the mechanical properties of the designed samples. Finally, to validate the results of the last step, the designed samples are going to be printed three-dimensionally before bearing standard tests such as pressure. By way of comparison of the acquired numerical results and laboratory models outcomes, the performed modelling is validated
  9. Keywords:
  10. Metamaterial ; Cubic Unit Cell ; Truncated Octahedron Unit Cell ; Truncated Cube Unit Cell ; Non-Diamond Unconventional ; Pentamode ; Mechanical Properties

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