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Biomimetic patterns in 3D printed auxetic metamaterials
Bečka, Filip ; Vozárik, Andrej (oponent) ; Lepcio, Petr (vedoucí práce)
The master’s thesis deals with the implementation of biomimetic patterns into 3D printed structures, focusing on the study of auxetic behaviour and mechanical properties. For this purpose, six types of structures were designed and prepared using fused deposition modelling. Polyethylene terephthalate glycol (PET-G) was chosen as the printing material. Mechanical testing involved static compression tests supplemented with video recordings, which served to determine Poisson's ratio and to study the effect of implemented reinforcement on the deformation behaviour of the structures. The proposed biomimetic reinforcement further increased the already good energy absorption efficiency of the auxetic structures. At the highest level of reinforcement, significantly more uniform macroscopic deformation of the structure was observed. The reinforcement also led to an increase in the yield stress and specific modulus in auxetic structures. In contrast, in non-auxetic structures, the addition of reinforcement resulted in a decrease in specific modulus. Finally, the influence of reinforcement on the auxetic behaviour of the structure was examined. The incorporation of reinforcing elements led to an increase in Poisson's ratio, but not to a transition to positive values. A significant boundary effect was observed in the structures, with different values of Poisson's ratio measured in different parts of the prepared structures.
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Polymeric metamaterials with advanced mechanical properties
Štaffová, Martina ; Lehocký,, Marian (oponent) ; Kotoul, Michal (oponent) ; Jančář, Josef (vedoucí práce)
Thesis deals with 3D printed polymeric auxetic structures with an emphasis on their mechanical performance. Different designs of auxetic re-entrant cell architectures were used to enhance mechanical properties, especially the energy-absorption-to-weight ratio under compressive loading. The lattice structures were 3D printed by vat photopolymerization masked-stereolithography technique. A novel tool for the complex characterization of 3D printed bodies was developed and systematically demonstrated employing a commercial free-radical photopolymerization resin. The method relies on superimposed static and oscillatory mechanical test combining the heat deflection temperature (HDT) measurement with the dynamic mechanical analysis (DMA) in a single test for fast and reliable characterization of parameters determining the curing behavior of the photopolymer. The influence of printing conditions and post-curing time was investigated to elucidate their effects on residual stresses in 3D-printed cellular bodies. The auxetic architectures were printed using flexible and stiff resins, and the effect of porosity, cell size, and structural gradients was investigated. The results were evaluated from a structural and material point of view, comparing materials above and below Tg. The best energy-absorbing performance was found in a biaxially graded structure with a center-wise location of the highest local porosity. The presented data contribute to a fundamental understanding of the effects of lattice architecture on the deformation response of auxetic structures and identifies routes for structurally tuning the auxetic structures mechanical performance. In addition, the results demonstrate the versatility offered by additive manufacturing techniques in physically realizing complex nature inspired structural architectures.
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Návrh kompozitního pohlcovače nárazu dle pravidel soutěže Formula Student
Janečka, Jiří ; Vaněk, František (oponent) ; Šplíchal, Jan (vedoucí práce)
Práce se zabývá jednou z možností vylepšení stávajícího řešení absorbéru nárazu pro monopost Dragon e3 týmu TU Brno Racing. První část práce obsahuje rešerši věnující se využití kompozitů při absorpci energie, mechanismům a poruchám probíhajícím při samotné absorpci. Dále jsou zmíněny a popsány nejpoužívanější koncepty pohlcovačů nárazu. Ve druhé části je proveden návrh a realizace technického řešení kompozitního absorbéru nárazu dle pravidel soutěže Formula Student. Toto řešení bylo poté otestováno na padostroji a změřena potřebná data. Na závěr byly vyhodnoceny výsledky pádových zkoušek, ty byly poté porovnány s daty simulovanými a byly provedeny korekce výpočtového modelu. Proběhlo i srovnání s předchozí generací absorbéru a byly popsány hlavní rozdíly. Pozornost byla věnována i poruchám vznikajícím při pádové zkoušce. Technické řešení bylo zhodnoceno a byly navrženy úpravy pro budoucí generace deformačních členů.
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