PSI - Issue 47

3

Liviu Marsavina et al. / Procedia Structural Integrity 47 (2023) 744–748 Author name / Structural Integrity Procedia 00 (2019) 000–000

746

Prusa MK3 printer, based on FDM technique was used for test specimen manufacturing. The printer was equipped with an HFE300 extruder for printing parts with filaments of 2.85 mm diameter. A 3D printing software was used to set the printing parameters such as raster angle, head speed, extrusion temperature and infill. The manufacturing parameters are presented in Table 1. The infill pattern at +/-45 grade was choose because was shown to have the higher mechanical properties, Ayatollahi et al. (2020).

Table 1. Manufacturing parameters for SCB specimens

Infill

Infill density [%]

Layer thickness [mm]

Average speed [mm/s]

Temperature build plate [ 0 C]

Temperature nozzle [ 0 C]

Maximum speed [mm/s]

Material

Rectilinear +/-45 grade

100

60

240

80

55

0.20

PETG

3. Testing conditions Tests were carried on a Zwick ProLine Z005 testing machine (maximum load 5 kN) at room temperature and with a load speed of 2 mm/min. Symmetric three point bending configuration was employed for the tests with a span S = 0.8 R, Fig. 2. Five specimens were tested for each geometry. The fractured V-notch specimens after test can be seen on Fig, 3

2S

Fig. 2. SCB specimens in three point bending fixtures.

Fig. 3. The fractured SCB V-notch specimens.

4. Results and discussions The results on fracture load P max versus specimen radius R are presented in Fig. 4, while Fig. 5 show the fracture energy, up to maximum load, W versus specimen radius. The mean value of the fracture load resulted from the testing program are shown in Fig. 4. It could be observed that the fracture load increases with increasing the specimen size with 130% for V-notch geometry, 155% for specimens with rounded notches of 0.8 mm, respectively 180% for specimens with rounded notches of 2.2 mm. These maximum differences were obtained comparing the specimens with radius R = 10 mm with those with R = 40 mm. Comparing the fracture load of V-notch specimens with the round notches with 0.8 radius it could be observed that the fracture load increases with around 24%, respectively with around 45% for rounded notches with  = 2.2 mm radius. The same tendency could be observed for energy versus specimen radius, Fig. 5. On one hand, the energy increases with the specimen size for all three types of notched geometries. On the other hand, the fracture energy increases increasing the notch radius, from V-notch (  = 0) to round notch with notch radius  = 2.2 mm.