PSI - Issue 56

Vasilica Ioana Cimpoies et al. / Procedia Structural Integrity 56 (2024) 49–57 Author name / Structural Integrity Procedia 00 (2019) 000–000

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structures have garnered significant attention. This attention is owed to their optimization through the application of minimum weight design principles, comprehensive dynamic and quasi-static experimentation, and the employment of large-scale computer simulations. (Cernescu, 2014). The provided images below depict the sequential stages involved in achieving the optimal design, progressing from the initial paper concept to the final 3D-printed samples.

Fig. 1. Paper quilling model

Fig. 2. 2D view of one cell of the metamaterial with geometrical dimensions

Fig. 3. Geometrical pattern of the metamaterial

Fig. 4. 3D printed structure

2.2. Material and Manufacturing Method In order to create the distinct meso-structure and material design of metamaterials, special manufacturing techniques are necessary. These techniques must be creative and advanced in nature. 3D printing presents a disruptive manufacturing process which combines molding principles with unique benefits such as the ability to create complex geometries, customization, and quick manufacturing. Due to these advantages, 3D printing is increasingly used to fabricate mechanical metamaterials with intricate internal structures (Zhou, 2023). The manufacturing method selected for all the samples was 3D printing, due to accessibility and ease in creating complicated structures such as spiral patterns. The material chosen for 3D printing was Z-ultrat, an ABS plastic blend filament. When printed this material yields a consistent surface texture and exhibits properties similar to those of models produced through injection molding. Z-ultrat is characterized by its widespread availability, user-friendly nature, and its ability to sustain intricate structures via a single production process. Furthermore, one of the advantages associated with Z-Ultrat is its versatility in conducting a wide range of physical tests, thereby offering precise and relevant information into the response of a component to its environment. (Szykiedans, 2016). Standard tensile samples of the material were produced for experiments, using similar printing parameters to get the material constants of the 3D printed metamaterial. The specimens printed with 100% infill rate and +45-45 infill pattern, had a cross-sectional area of 9.57 mm by 4 mm. They were tensile tested up to a maximum force of 1,100 N at a speed of 4 mm per minute. Tensile strength testing revealed values of 28.75 MPa, 0.3 for Poisson's ratio, and 1703 MPa for Young's modulus. Due to air to void ratio of the 3D printed materials, the above values were obtained based upon the methodology described by Racz and Dudescu (2022). 2.3. Testing methods Due to the spiral shapes, when these structures are subjected to loads was observed that the inside cells present in plane displacements and rotations around the vertices of the spiral centers (denoted in the displacement-load scheme with “O” – Fig. 5). The movements have been visible during the experiment, but we were limited for measuring the displacements on the testing machine. In order to understand the reaction in the structure have been chosen three methods of analyses:  Physical compression tests of the 3D-printed samples on a universal testing machine;  Finite Element Method using Ansys Workbench software;  Digital Image Correlation (DIC) method.