PSI - Issue 61

Albert E. Patterson et al. / Procedia Structural Integrity 61 (2024) 148–155 Author name / Structural Integrity Procedia 00 (2024) 000–000

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provided the best option. Beginning with that information, this section examines the e ff ects of element layout on the fracture load. The fracture load was selected as the response, as it gives a more consistent and understandable output than a conditional fracture toughness K Q . The samples used do not meet the criteria for plane strain given by ASTM D5045, as is typical for FFF-processed materials. Therefore, maximum load at fracture was taken as the response to allow better direct comparison of the behavior. This is followed in the discussion section by qualitative crack analysis. In this test series, the three materials of interest (ABS, PLA, PC) were printed using the same print parameters used for the notching method analysis and pre-cracked using machined notches. Four di ff erent print layouts were used ( ± 45 ◦ raster, 0 / 90 ◦ rater, gyroid, and concentric around the crack tip) with two di ff erent nozzle sizes (0.6 mm and 0.8 mm). This was replicated three times for a total of n = 72. The printing patterns and example specimens are shown in Figure 2. The experimental design is shown in Table 2, while the results are shown in Table 2 and Figure 3. Testing speed was 10 mm / min.

0.6 mm gyroid

0.8 mm gyroid

0.6 mm concentric 0.8 mm concentric

0.8 mm R90

0.8 mm R45

0.6 mm R90

0.6 mm R45

Fig. 2. Material element layouts, showing g-code and example printed samples. Note that the printed samples are shown before notching.

0 100 200 300 400 500 600 700 800 900 1000 Maximum Force at Fracture (N) ABS Cases

0 100 200 300 400 500 600 700 800 900 1000 Maximum Force at Fracture (N) PLA Cases

0 100 200 300 400 500 600 700 800 900 1000 Maximum Force at Fracture (N) PC Cases

Fig. 3. Experimental results for ABS, PLA, and PC cases. Note that the error bars indicate standard error SE = σ/ √ n .

4. Analysis and Discussion

4.1. Statistical Analysis

Completing a statistical analysis (ANOVA) (Minitab V.20) on the results of the element layout tests, it is found that all three of the factors had a statistically significant impact on the fracture load at α = 0 . 05. The material choice had the largest impact ( p < 0 . 001, F = 63 . 17), while element layout had a smaller ( p < 0 . 001, F = 11 . 90) but still major impact. The nozzle size did show statistical significance ( p = 0 . 023, F = 5 . 40) but had a much lower impact than the material choice or layout. Figure 4a shows the main e ff ects plot for this experiment.