## 3 Results and Discussion

Table 1: Mechanical properties values derived from the force–displacement curves \({}^{1}\). Finally, it is necessary to verify that the value of the expression \(2.5\left(K_{Q}/\sigma_{Y}\right)^{2}\) is less than the thickness of specimen B, less than the initial notch length \(a\), and less than the ligament value \(\left(W-a\right)\). Notably, \(\sigma_{Y}\) is the value of the material's yield strength. Thus, after evaluating this validity, \(K_{Q}\) can finally be established as the value of the fracture toughness of the material: \(K_{Q}=K_{Ic}\). Table 3 shows the results of each test performed, including the average value of \(K_{Ic}\) for each printing orientation considered. This allows the establishment of a final average value of \(K_{Ic}=1.32\) MPa\(\cdot\)m\({}^{1/2}\) with a maximum standard deviation (SD) of 0.0687. The critical energy release rate \(G_{Ic}\) values for each test were calculated using the following equation [31]:  
\[G_{Ic}=\frac{\left(1-v^{2}\right)\ K_{Ic}{}^{2}}{E} \tag{3}\]  
Table 4 presents the values of the critical energy release rate at the time of fracture for each of the samples tested, along with the mean values and standard deviation. Figure 5 shows the fracture planes observed after testing the samples in different orientations: 0\({}^{\circ}\), 45\({}^{\circ}\), and 90\({}^{\circ}\). The direction of propagation of the crack is from left to right. The fracture planes are straight, located on the symmetry plane, and follow the normal direction of the applied load. The fracture planes observed in the specimens oriented in the three analyzed directions appear relatively similar, suggesting that the material exhibits consistent fracture behavior. Upon closer examination, however, distinct regions can be \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimens** & **0\({}^{\circ}\)** & **45\({}^{\circ}\)** & **90\({}^{\circ}\)** \\ \hline
1 & 4.31 & 3.75 & 4.23 \\
2 & 3.93 & 4.33 & 4.02 \\
3 & 4.67 & 4.61 & 4.20 \\ \hline Mean & 4.31 & 4.23 & 4.15 \\ SD & 0.3734 & 0.4357 & 0.1150 \\ \hline \hline \end{tabular} \({}^{\dagger}\) Depending on the orientation of each print on the selected specimens. Source: own elaboration based on calculation results with Spyder (v. 5.5.1).  
\end{table} 
Table 4: Critical energy release rate values for the durable resin material (expressed in \(J/m^{2}\)) 1. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimens** & **0\({}^{\circ}\)** & **45\({}^{\circ}\)** & **90\({}^{\circ}\)** \\ \hline
1 & 1.34 & 1.25 & 1.32 \\
2 & 1.27 & 1.34 & 1.29 \\
3 & 1.39 & 1.29 & 1.32 \\ \hline Mean & 1.33 & 1.32 & 1.31 \\ SD & 0.0579 & 0.0687 & 0.0182 \\ \hline \hline \end{tabular} \({}^{\dagger}\) Depending on the orientation of each print on the selected specimens. Source: own elaboration based on calculation results with Spyder (v. 5.5.1).  
\end{table} 
Table 3: Fracture toughness values for durable resin material (expressed in MPa\(\cdot\)m\({}^{1/2}\)) 1.  
observed, exhibiting certain preferences concerning crack orientation. The aforementioned regions are indicated in each photograph by a circle, thereby signifying the orientation of the cracks.