Dynamic behaviour of 3D printed periodically structured mechanical metamaterials: experimental investigations and computational simulations

The thesis work is carried out at the dynamic acceleration and vibration laboratory of INRIM (Istituto Nazionale di Ricerca Metrologica) which is a public research centre and is Italy's national metrology institute (NMI) located at Turin. This research represents an overview of mechanical periodically structured materials as well as a more comprehensive investigation on 2D metamaterials capable of reducing transition of mechanical wave. While most of the previous research projects were focused on designing periodic structures by topology optimisation tools and computational simulations, The objective of this research is to experiment, and Validation of the designed metamaterials and the ones extracted from related research works by the experimental setup which is realized in INRIM research centre. In the first chapter, literature review is performed a general overview of metamaterials will be made: the definition and etymology of the word will be discussed, and the main typologies created will be described, paying more attention to mechanical metamaterials especially the ones that are used to mitigate mechanical vibrations. to be more familiar with the vibrational behaviour of metamaterials, the definitions of the vibrational properties of the material and structures will be presented. In this section the Bloch’s theorem and Brillouin zone will be described which is the base of investigations in periodic structures. In the second part instrumentation and the method used for experiments are introduced, the required information about experimental devices, fabrication method and material’s properties are elaborated and the specimens designed and experimented are introduced. In the third chapter which is the main part of the project, the results of the experiments will be discussed in detail. Effects of various geometrical shapes in the structure will be analysed and results of the COMSOL Multiphysics simulation will be discussed and a comparison between the metamaterials will be carried out. Finally, after foreseeing some possible applications, the conclusion will be elaborated.