Additive Manufacturing of chiral/anti-chiral structures and their characterizations

Date

2023-3

Author

İnan, Cevher Yusuf

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In this thesis, tri-chiral and anti-tri-chiral lattice geometries with negative Poisson's ratio behavior were fabricated with additive manufacturing and the material characterizations of the structures were defined. Tensile and compression specimens were designed by forming the unit cells of auxetic structures with various geometric dimensions. Designed samples were manufactured by a 3D printer with PLA filament and subjected to mechanical tests. Stress-strain curves of the structures were obtained and the mass-normalized strengths were calculated. Obtained experimental results were compared with each other in terms of geometric dimensions and cell orientation. The material model of the PLA used in this study was created in the finite element model according to the Johnson-Cook material model and verified. Finite element models of the selected chiral and anti-chiral structures were constructed. Two different solution algorithms were preferred for the finite element analysis and Optistruct and Radioss solvers were employed. The error rates of the finite element solution algorithms were calculated and the results were compared. Computational stress-strain curves were constructed and compared with experimental ones. When the curves were examined, it was observed that the material behaviors of the chiral and anti-chiral structures were different for the computational model and experimental results. In addition, structural characterization tests such as XRD, SEM, FTIR, TGA, and DSC were applied to the samples and the results were evaluated. Finally, multiple regression analysis was applied with experimental data. As a result, it was seen that ligament length and thickness have a significant effect on strength. Also, in general, chiral structures have better mechanical properties than anti-chiral structures.

Subject Keywords

Auxetic Materials, Additive Manufacturing, Lattice Structures, Negative Poisson’s Ratio, Finite Element Analysis

URI

https://hdl.handle.net/11511/102783

Collections

Graduate School of Natural and Applied Sciences, Thesis