PSI - Issue 61

Bahman Paygozar et al. / Procedia Structural Integrity 61 (2024) 232–240 Paygozar et al./ Structural Integrity Procedia 00 (2019) 000 – 000

237

6

4.1. Experimental results The load-displacement responses of three SENB samples obtained from the 3P bending tests for each print orientation are plotted in Fig. 4. The peak load ( ) of each curve was used as the critical load ( F cr ) in Eq. (1) for calculating the corresponding fracture toughness (K IC ). The computed fracture toughness values are shown in Table 2. The corresponding values of fracture energy (i.e., ) were also extracted through Eqs. (3) and (4) considering the plane strain case.

Pre-crack (Notch)

Fig. 3 The configuration of the SENB specimen model along with the pre-crack (notch) location and boundary conditions.

The Young’s Modulus values required in Eq. (4) were determined as 3.19, 3.5, and 3.31 GPa for the vertically, laterally, and horizontally fabricated dog-bone specimens, respectively. The plane strain case was considered in Eq. (4), where =0.33 was used in this study for the PLA material (Ferreira et al. 2017). Additionally, the dog-bone specimens were manufactured and tested according to ASTM D638. The DIC method was utilized to extract the samples' mechanical properties.

(a) (c) Fig.4 The load-displacement curves extracted from 3P bending tests on the SENB specimens fabricated with (a) horizontal, (b) lateral, and (c) vertical print orientation. (b)

Table. 2 The fracture properties of PLA extracted through SENB specimens for different print orientations. Sample 1 Sample 2 Sample 3

Average values

K IC [ √ ] 4.29 4.27

K IC [ √ ] 4.18 4.29

K IC [ √ ] 4.19 3.99

K IC [ √ ] 4.22 4.18

G [N/mm]

G [N/mm]

G [N/mm]

G [N/mm]

Horizontal

4.95 4.64 3.34

4.70 4.69 3.87

4.73 4.05 3.42

4.79 4.46 3.54

Lateral Vertical

3.46

3.72

3.50

3.56

4.2. Crack propagation Crack propagation in the SENB samples additively manufactured in three different print orientations is shown in Fig. 5. Generally, crack propagation experienced through damage in the material can be of interlayer and intralayer types or a mixture of both (Paygozar and Gorguluarslan 2023a). As shown in Fig. 5(a), in the horizontally printed specimens, the crack propagation was done in both interlayer and intralayer types. However, in the samples that were 3D printed laterally and vertically (Figs. 5(b) and 5(c)), the crack propagation occurred through pure intralayer and interlayer failure mechanisms, respectively.