H, CH-8092 Z ich, Switzerland Danish Technological Institute DTI, DK-2630 Taastrup, Denmark; [email protected] Mechanical Engineering Division, Frederick University, Nicosia CY-1036, Cyprus Frederick Study Center, Nicosia CY-1036, Cyprus Correspondence: [email protected]; Tel.: 357-2239-4360 (ext. 42115)Citation: Photiou, D.; Avraam, S.; Sillani, F.; Verga, F.; Jay, O.; Papadakis, L. Experimental and Numerical Evaluation of 3D Printed Polymer Tetra-Petal Auxetic Structures below Compression. Appl. Sci. 2021, 11, 10362. https://doi.org/10.3390/ app112110362 Academic Editor: Georgios E Stavroulakis Received: 7 October 2021 Accepted: 1 November 2021 Published: four NovemberAbstract: Auxetic structures possess a damaging Poisson ratio ( 0) as a result of their geometrical configuration, which exhibits enhanced indentation resistance, fracture toughness, and effect resistance, at the same time as exceptional mechanical response advantages for applications in defense, biomedical, automotive, aerospace, sports, customer goods, and personal protective gear sectors. Together with the advent of additive manufacturing, it has come to be probable to produce complicated shapes with auxetic properties, which couldn’t have been possible with classic manufacturing. Three-dimensional printing enables quick and precise control in the geometry and material composition from the creation of desirable shapes, giving the chance to discover unique geometric elements of auxetic structures having a range of unique materials. This study investigated the geometrical and material combinations that could be jointly tailored to optimize the auxetic effects of 2D and 3D complicated structures by integrating PHA-543613 site design and style, modelling approaches, 3D printing, and mechanical testing. The simulation-driven design and style methodology permitted for the identification and creation of optimum auxetic prototype samples manufactured by 3D printing with diverse polymer materials. Compression tests had been performed to characterize the auxetic behavior from the various technique configurations. The experimental investigation demonstrated a Poisson’s ration reaching a worth of = -0.6 for specific shape and material combinations, hence giving support for preliminary finite element research on unit cells. Ultimately, depending on the experimental tests, 3D finite element models with elastic material formulations had been generated to replicate the mechanical performance from the auxetic structures by implies of simulations. The findings showed a coherent deformation behavior with experimental measurements and image analysis. Key phrases: auxetic structures; additive manufacturing; SLS; FDM; quasi-static compression testing; FEAPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.1. Introduction Many of the main structural positive aspects of sandwich composites are the Diversity Library Storage higher stiffnessto-weight ratio along with the higher bending strength-to-weight ratio. The sandwich increases the flexural rigidity of structures without the need of adding substantial weight. The design and style and manufacturing of lightweight composite structures for protective purposes are of interest for both defense and civilian applications, including aircraft, sports, automotive, and consumer goods [1,2]. Sandwich structures demonstrate fascinating characteristics, for example high-energy absorption capacity, higher strength, and enhanced stability [3]. A conventional sandwich panel consists of a low-density core, mainly i.