RESUMO A Impressão 3D baseada em extrusão se popularizou muito nos últimos anos devido ao surgimento de projetos de código aberto e máquinas de baixo custo, que tornaram a tecnologia acessível a todos os níveis de usuários. Paralelamente, novos materiais, em geral filamentos termoplásticos, são inseridos no mercado para aplicação neste tipo de técnica de fabricação, tornando cada vez mais necessário o desenvolvimento de estudos de caraterização experimentais dos materiais para fornecer dados técnicos aos utilizadores. Neste trabalho estudou-se o poli(tereftalato de etileno glicol) (PETG), polímero de recente adoção neste contexto, comparando-o ao poli(ácido lático) (PLA), o mais popular no âmbito da tecnologia. Ambos os materiais foram analisados mecanicamente à tração, através de amostras fabricadas por Impressão 3D variando os ângulos de deposição do material extrudado. Para a mesma análise, visando comparação, foram construídas peças por moldagem por injeção. Os materiais em seu estado inicial filamentar foram avaliados termicamente por TGA e DSC, e quimicamente por FTIR. As duas últimas técnicas de caracterização também foram aplicadas aos polímeros após o processamento por injeção e impressão. Os resultados obtidos mostraram que as propriedades mecânicas à tração dos componentes impressos são fortemente influenciadas pela orientação dos filamentos depositados nas camadas e pela mesoestrutura das peças. O PLA dispõe de superioridade mecânica, maior tensão máxima e elevada rigidez em relação ao PETG, nas amostras injetadas e impressas. O PETG, por sua vez, demostrou ser um material mais resistente à degradação térmica, mais estável termicamente (por não apresentar alterações significativas em seu comportamento térmico após ser processado), e flexível, propriedade esta que o torna muito interessante para aplicações na Impressão 3D. Por fim, a estrutura química molecular dos polímeros foi semelhante à descrita em outros estudos da literatura e pouco alterada pelos processos de fabricação.
Purpose This paper aims to evaluate the influence of the parameters of the Fused Filament Fabrication (FFF) process on the mechanical properties and on the mass of parts printed in Polylactic Acid (PLA). In addition, the authors developed predictive models for the analysed responses. Design/methodology/approach A full Factorial type of experimental planning method was used to define the conditions for manufacturing parts according to the variation of the construction parameters, extrusion temperature and print speed. Samples were printed for tensile, flexion and compression tests. Their mass was measured. Multiple regression methods, based on power equations, were used to build the forecasting models. Findings It was found that the extrusion temperature was the parameter of greatest influence in the variation of the analysed responses, mainly because it generates behaviour patterns and indirectly demonstrates thermal/rheological characteristics of the material used. Print speed affects responses, however, with variations dependent on part geometry and printer hardware/software. It was possible to establish prediction models with low error rates in relation to the experimental values. Originality/value The study demonstrates a good relation between the use of a structured experimental planning method as the basis for the development of predictive models based on mathematical equations, the same structure of which can be used to describe different responses.
Polylactic acid (PLA)—based honeycomb samples with different cell sizes and thickness were prepared using the fused filament fabrication (FFF) 3D printing technology and used to build sandwiched multilayer structures consisted of the honeycomb as the core component and poly(vinylidene fluoride) (PVDF) and/or PVDF/carbon nanotube (CNT) nanocomposites as top and bottom layers. The effect of the honeycomb design (cell size and thickness) and the presence and nature of the impedance matching layer on the microwave absorbing properties of the corresponding structures was investigated in the X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz). For the systems without matching layer or with neat PVDF film as the matching layer, the honeycomb with larger thickness (5 mm) and larger cell size resulted in better electromagnetic wave attenuation but narrow frequency bandwidth with RL below −10 dB. The best combination minimum RL value (−18 to −14 dB) and broad frequency bandwidth with attenuation higher than 90% (around 8 GHz) was achieved with honeycomb of 2 mm thickness sandwiched by PVDF/CNT05 as the matching layer and bottom layer constituted by PVDF/CNT1 film, regardless the cell size of the honeycomb. These results indicate the PLA honeycomb as promising candidate as component for multilayer microwave absorbing materials and open new possibilities of applications of FFF technology for designing flexible, lightweight, and low‐cost materials to be used in both civil and military industries.
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