## 3 Results and Discussion
### Mechanical Properties
#### 3.2.2 Flexural Tests  
The three-point bending tests were performed according to ASTM D790-17 standard; the statistical analysis of flexural strength and modulus results is reported in Table 4.  
As previously observed for tensile properties, the \(p\)-values indicate that there is was a significant difference among building orientations for the flexural properties under investigation. The [PERSON]'s HSD post hoc test was performed with the aim of identifying which building direction was significantly different from the others. Table 5 reports the values of flexural strength, elastic modulus, and flexural strain in term of means and standard deviations for each building direction. These results confirm that samples with XZ orientation showed the best mechanical performances; in fact, the [PERSON]'s HSD test revealed the significantly highest flexural strength and modulus for XZ samples compared to the other building directions. These values of flexural properties are slightly higher with respect to those reported in the material datasheet (these latter refer to samples built by using Fortus 3D printer setting default process parameters defined by Stratasys), as previously observed for tensile properties. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mechanical Property** & **Source** & **Sum of Squares** & **F Ratio** & \(p\)**-Value** \\ \hline \multirow{2}{*}{Flexural strength} & BG & 3422.889 & \multirow{2}{*}{767.521} & \multirow{2}{*}{<0.001} \\  & WG & 4.460 & & \\ \hline \multirow{2}{*}{Elastic modulus} & BG & 295,285.267 & \multirow{2}{*}{208.456} & \multirow{2}{*}{<0.001} \\  & WG & 1416.533 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: ANOVA test for flexural strength and modulus. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **XY** & **XZ** & \multicolumn{2}{c}{**ZX**} \\ \cline{2-5}  & **Experimental** & **Experimental** & **Datasheet** & **Experimental** & **Datasheet** \\ \hline \multirow{2}{*}{Flexural strength [MPa]} & \multirow{2}{*}{109.72 (0.81) b} & \multirow{2}{*}{117.98 (0.26) c} & \multirow{2}{*}{112} & \multirow{2}{*}{69.98 (3.67) a} & \multirow{2}{*}{68} \\  & & & & \\ \hline \multirow{2}{*}{Flexural modulus [MPa]} & \multirow{2}{*}{2315 (58) b} & \multirow{2}{*}{2428 (17) c} & \multirow{2}{*}{2300} & \multirow{2}{*}{1963 (27) a} & \multirow{2}{*}{2050} \\  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Flexural properties of Ultem 9085 with XY, XZ, and ZX orientations, means, and standard deviations (in parentheses). Superscript letters indicate statistically homogeneous subsets ([PERSON]’s HSD test, \(\alpha=0.05\)). Specimens with XY orientation had significantly lower flexural properties than XZ samples. This is in good agreement with the results obtained by [PERSON] et al. (2018) on samples printed using similar process parameters. Moreover, according to [PERSON] et al. (2018) the better flexural strength of XZ coupons with respect to XY ones can be attributed to the different arrangement of contour in samples with different building orientation. When a flexural load is applied, the top surface of the specimen experiences compression, while the bottom one is under tension. In the case of XZ specimens both the top and bottom surfaces, where the stress is maximum, are mainly constituted by the contour. The presence of filaments perpendicular to the load application allow higher resistance value to be obtained. On the contrary, in XY samples the two load-bearing surfaces are mainly constituted by the infill, while the contour is only a small fraction located in the external part of the surface. This decreases the maximum load that the samples can withstand. A significant worsening of flexural behavior was observed for ZX samples. Their flexural strength and modulus were about 40% and 20% lower than the values observed for XZ samples. Moreover, XY and XZ samples plastically deformed until the maximum value of strain was reached.