PSI - Issue 37

S. Valvez et al. / Procedia Structural Integrity 37 (2022) 738–745 S. Valvez et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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curvature radius (1/R) observed in the specimens for the different conditions analysed. Conclusions based on these considerations will be drawn.

2. Materials and Methods The B2X300 printer was used to extrude the initial 1.75 mm diameter filament through a 0.6 mm diameter nozzle. The extruded filament is placed on a platform heated by a print head in a user-defined pattern to achieve the desired flat shape. Once a particular layer is finished, the print head is raised and continues to deposit the next layer. Using this equipment and methodology, specimens with dimensions of 85×12.7×4 mm 3 were printed. In terms of materials, Poly(ethylene terephthalate)-Glycol (PETG) is one of the most used materials in 3D printing technology due to its chemical alkali resistance, transparency, gloss, low haze, good printability, among other benefits. However, the addition of carbon fibre further expands its field of application because the composite becomes more resistant and resilient, as well as significantly reducing the risk of warping. In this case, it becomes an excellent choice for automotive and other industrial applications. On the other hand, when reinforced with aramid fibres, applications can be extended to sectors where high resistance to friction and impact is expected. Therefore, given the benefits reported for these materials, PETG, GFPETG and KFPETG were the filaments selected to obtain the specimens used in this study. Different printing parameters were used and Table 1 shows those that optimized the mechanical properties of these materials. The direction of deposition angle is according to the x-axis and all samples were printed with a raster angle of 0°. After printing, the specimens are placed on an aluminium plate coated with a Teflon film, to avoid any adhesion of the polymer to the aluminium, and the system placed in an oven (Heraus, model UT 6060), for a certain time and temperature. According to the literature, Bhandari et al. (2019), Table 2 summarizes the temperature and exposure time studied for all materials.

Table 1. Printing parameters for each material. Material Extrusion Temperature [ºC]

Speed [mm/s]

Layer Height [mm]

Infill [%]

PETG

265 195 265

20 60 20

0.4

100 100 100

PETG CF PETG KV

0.52 0.35

Table 2. Annealing conditions for all materials. Samples Group

Temperature [ºC]

Time [min]

1 2 3 4 5 6 7 8 9

90 90 90

30

240 480

110 110 110 130 130 130

30

240 480

30

240 480

The bending tests were carried out in accordance with the ASTM D790-17 standard, with a span of 64 mm, in a Shimadzu universal testing machine, model Autograph AG-X, equipped with a 10 kN load cell. For each condition, 5 specimens were tested at room temperature and at a displacement rate of 2 mm/min. The bending strength was calculated as the nominal stress at middle span section and using the maximum load value, according to the following equation: