PSI - Issue 61

Jose Beltra Mira et al. / Procedia Structural Integrity 61 (2024) 156–163 Author name / Structural Integrity Procedia 00 (2024) 000–000

159

4

Table 3. Experimental results (maximum fracture load) with mean and standard error SE = σ/ √ n .

Fracture Load (N)

SE = σ/ √ n

Combination Material

W (mm)

B (mm)

R1

R2

R3

Mean

1 2 3 4 5 6 7 8 9

ABS

30 30 30 40 40 40 50 50 50

6 6 6 8 8 8

318.8 327.8 332.1 326.2 515.3 605.3 616.7 579.1 617.3 695.8 550.4 587.5 535.1 529.3 600.3 554.9 782.2 961.3 812.9 852.1 980.6 939.2 1076.5 998.8 744.9 785.1 698.0 739.7 796.3 1127.8 1287.1 1070.4 1476.9 1531.1 1396.5 1468.2

3.9

PC

32.1 19.7 22.8 55.3 40.7 27.9

PLA ABS

PC

PLA ABS

10 10 10

PC

144.6

PLA

39.1

Collected Experimental Data

1000 1200 1400 1600

0 200 400 600 800

ABS W = 30 mm PC W = 30 mm PLA W = 30 mm ABS W = 40 mm PC W = 40 mm PLA W = 40 mm ABS W = 50 mm PC W = 50 mm PLA W = 50 mm Fracture Force (N)

Fig. 3. Collected data means for each case. Note that the error bars indicate standard error SE = σ/ √ n .

Table 4. Calculated conditional fracture toughness K Q and minimum B , a , and ligament L = ( W − a ) required to meet the plane strain specifications for ASTM D5045.

K Q ( MPa · m 2 (mm) R1 R2 R3 R1 R2 R3 0 . 5 ) 2 . 5( K Q /σ y ) 2.72 2.77 2.80 17.7 18.3 18.7 4.79 5.35 5.54 19.5 24.3 26.1 5.24 5.03 4.68 30.0 27.7 23.9 3.05 3.13 3.31 22.2 23.4 26.2 4.72 5.27 4.90 18.9 23.6 20.4 5.38 5.34 5.92 31.6 31.1 38.3 3.04 3.10 2.97 22.1 22.9 21.1 3.44 4.84 5.37 10.1 19.9 24.5 5.82 6.02 5.56 37.0 39.6 33.8

Combination Material

W (mm)

B (mm) L = ( W − a ) (mm)

1 2 3 4 5 6 7 8 9

ABS

30 30 30 40 40 40 50 50 50

6 6 6 8 8 8

15 15 15 20 20 20 25 25 25

PC

PLA ABS

PC

PLA ABS

10 10 10

PC

PLA

4. Analysis and Discussion

4.1. Statistical Analysis

Figure 4 shows the calculated means and standard errors of K Q for each specimen size relative to the material choice. While there is some di ff erence in the means between sample sizes for each material, a general trend is not observed and the di ff erences are not great. Therefore, a statistical analysis is necessary to determine is there is indeed a di ff erence (and therefore K Q K IC ) or if the di ff erences are noise in the data introduced by the print defects present in all AM parts. The most important question when examining the data collected from this study is whether there is a significant dependence of the K Q values on the sample size. It is expected that there will be for most materials including metals, ceramics, and plastics [16–18], as none of the samples meet the requirements established by ASTM D5045 for plane strain (the point after which size dependency disappears). To answer this, an Analysis of Variance (ANOVA) was