PSI - Issue 56

Sergiu-Valentin Galațanu et al. / Procedia Structural Integrity 56 (2024) 138– 143 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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To manufacture the specimens from the recycled filament, but also from raw filament infill, speed was set to 80mm/s, with a layer thickness of 0.2mm and 100% rectilinear infill. The nozzle temperature for the first layer was 240°C and 250°C for other layers. The bed temperature was 85°C for the first layer and 90°C for the other layers respectively.

0.0 0.5 1.0 1.5 2.0 2.5

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1.88

1.87

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1.85

1.84

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Average of the Diameter

Lenght [m]

Fig. 1. (a) Felfil evo filament extruder and (b) average of the diameter in length

Tensile test specimens with the following dimensions were used: 2mm in thickness, 5mm in width and the calibrated area of the length 40mm, respectively. The specimens were subjected to tensile testing using a universal testing machine (Zwick Proline Z005, Ulm, Germany), with a maximum force of 5 kN at ambient temperature. To determine Young's Modulus a manual clip-on extensometer was used for some of the tests. The Digital 3D Image Correlation System Q-400 was used for the other tests. In the first step, the calibration procedure was realized. The calibration process was carried out with a BNB9x9. For these tests, the Global Residual was 0.240, and a medium accuracy is between 300 and 500. Images of the specimens were captured at a rate of 1 Hz, one picture for each camera at one second. Next, the specimens were painted with several layers of white paint until the surfaces of the specimens were completely white and without reflectivity. In the end, a second light-speckle pattern of black paint was applied over the area of interest. The specimens were tested as follows: PETG Transparent Recycled specimens, PETG Transparent specimens, PETG White specimens, and PETG Black specimens. 3. Results and discussions The aim of this paper was to observe the behavior of recycled and raw specimens. In order to understand this behavior, different charts were plotted for each type of specimen. Fig. 2 presents stress – strain curves for the same type of specimens. For a better observation and comparison of the results obtained for each type of material, the stress-strain curves were cut at 0.2 mm/mm. However, some of the specimens failed at much higher strain values, but this aspect can be observed in Fig. 3 c. Taking into account those results, the average of the maximum stress, the average of the strain at maximum stress, and the average of the ultimate strain were obtained, in Fig. 3. The Young Modulus was determined only for the recycled specimens and for the black specimens.

Fig. 2. Stress – strain curves for (a) PETG Transparent Recycled specimens, (b) PETG Transparent specimens, (c) PETG White specimens, and (d) and PETG Black specimens.

It can be seen that the maximum stress average has similar values for all the groups of specimens investigated. Both transparent specimen groups, from recycled material and from raw material, have a maximum stress of about