Caracterização de corpos de prova de poliácido-láctico reforçado com grafeno produzidos por fabricação por filamento fundido

• Autor(a) principal: Silva, Diego Moreira da
• Data de Publicação: 2022
• Outros Autores: [e-mail]
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/17791
• topic: Engenharia mecânica; Engenharia de materiais; Resistência de materiais; Polímeros; Mechanical engineering; Materials engineering; Strength of materials; Polymers; ENGENHARIAS::ENGENHARIA MECANICA::MECANICA DOS SOLIDOS

This work studied the influence of graphene on polylactic acid (PLA) with samples made by 3D printing, fused filament fabrication (FFF) technique. It was seen, preliminarily, that the presence of graphene reduced the Vickers microhardness and in the sample of polylactic acid with graphene (GPLA) there was a reduction of the hardness due to the reduction of the layer thickness of the sample. Because of the microhardness reduction, the influence of 3D printing parameters by the FFF technique on Vickers microhardness in PLA sample was studied in order to obtain a combination that optimizes hardness gains and can be reproduced for the GPLA material. The Vickers microhardness test loads were 25, 50, 100 and 200 g. The studied parameters of the FFF technique were fill density (20%, 40%, 60%, 80% and 100%), fill pattern (concentric, grid and line) and layer thickness (0.1 mm and 0.2 mm). The combinations of printing parameters add up to 30 possibilities that, when applied, the 4 loads generate 120 cases and each microhardness test requires a minimum of 10 indentations, totaling 1200 measurements. The average microhardness of PLA is 17.81 HV. These data were evaluated by ANOVA in order to verify if there is statistical validation according to the hypothesis test. Meyer lines were analyzed characterizing the load as an irrelevant factor in the microhardness variation. Thus, the ANOVA applied in the study consisted of three factors. Tukey's test was used indicating that the parameters separately and the two-by-two interactions pointed to the combinations of maximum microhardness values. The combinations that resulted in the highest microhardness values were compared for filament consumption, manufacturing time and relative to average microhardness gain. The best combination is 0.2mm layer thickness, grid fill pattern, and 40% fill density. This combination has a hardness of 20.16 HV with a relative gain of 13.19 % on average for PLA and consumed 879 mm of filament during 9 minutes and 43 seconds of sample production. Compression, bending, tensile and tribological tests were applied to samples of PLA and GPLA produced by FFF. Addition of graphene improved the compression and bending properties. In the tensile test, there was a loss of ductility, an increase in Young's modulus and Poisson's ratio. Tribological tests showed a reduction in the coefficient of friction due to graphene. Characterizations were made by optical microscopy, Raman spectroscopy and scanning electron microscopy (SEM). SEM showed tubular nanostructures in the GPLA samples.