محمدصادق ابراهيمي

Metamaterial is a material that is engineered to have properties that are not found in common materials. Metamaterials do not derive their properties from the parent material, but their properties are designed based on the new structure. auxetic is a group of metamaterials that exhibits a negative Poisson's ratio.four Novel hybrid metamaterial structures by combining honeycomb, re-entrant, and star-shaped unit cells were developed and fabricated by additive manufacturing techniques and tested for the very first time to eva‎luate the enhanced mechanical properties. The mechanical properties of the parent material were characterized using the digital image correlation (DIC) method. DIC test outputs, including Young's modulus, Poisson’s ratio, and yield stress, had good repeatability and were used as inputs to define the material in numerical simulation. In-plane uniaxial compressive response and energy absorption capacity of novel structures were compared using finite element simulation and experimental methods. In addition, the failure modes and mechanism of deformation of all structures were explained in detail. A type one re-entrant-star-shaped (RS1) structure demonstrated higher compressive strength, plateau stress, and energy absorption than other structures. Also, This study aims to investigate the effects of the curvature and angle of the edges and feather points of auxetic structures and investigate the mechanical properties of the stents as a result of these parameters. Initially, a unit cell was developed, then by modifying the curvature and angle of the edges, two more units were generated, and auxetic structures were designed according to these unit cells. An assessment of the mechanical properties of designed structures has been performed by experimental testing and validated by finite element analysis. It was observed and explained in detail how deformation mechanisms and mechanical properties in different structures are affected by curvature and angle.

Mohammad Sadegh Ebrahimi

Dr. Ramin Hashemi