## 3 Results and Discussion
### Mechanical Characterization  
The electrical characterization highlighted a percolation threshold very close to a 4% content of xGNPs; therefore, the investigation of the mechanical properties concerned only two mixture compositions, i.e., 6% and 10%, which were compared to the pure powder samples. Figure 10 shows representative trends, over five replicas, of the stress-strain diagrams obtained during the tensile and the three-point bending tests, while Table 5 collects the resulting properties. The results highlight that the addition of the nanoplatelets to the pure material negatively affected the mechanical properties of the fabricated samples, and the effect was more pronounced the higher the weight percentage of the additive, with an overall average deterioration of around 28% for 6% xGNPs and 40% for 10% xGNPs, with a major effect on the ultimate strength, which was somewhat more than halved at 10% if compared to the starting material, while the other properties decreased by an average of around 41%. These findings can be attributed to the sintering process, which is not able to guarantee the melting and complete incorporation of the nanoplatelets within and between the PA12 powder particles, due to their thermal inertia, promoting pore formation, as can be clearly seen in Figure 11, which constitute defects and trigger breakage of the samples with lower applied loads [31]. In fact, graphite and polyamide, while not inherently incompatible, do present challenges in achieving optimal composite properties due to differences in their surface energies and structures. Graphite's layered structure and low surface energy can lead to poor dispersion and adhesion within the polyamide matrix [67]. The relatively low surface energy of graphite compared to the polyamide matrix can lead to weak interfacial bonding, resulting in poor load transfer between the filler and the polymer [68]. However, modifying the graphite surface with functional groups can increase its surface energy and  
Figure 10: Mechanical characterization results: (**a**) tensile; (**b**) three-point bending. The curves are representative of the trends obtained over 5 replicates. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**xGNPs [\%]** & \(E_{T}\) **[GPa]** & \(E_{F}\) **[GPa]** & \(\sigma_{T,Y}\) **[MPa]** & \(\sigma_{F,Y}\) **[MPa]** & **\(UTS\) **[MPa]** & **\(UFS\) **[MPa]** & \(\epsilon_{T,R}\) **[\%]** & \(\epsilon_{F,R}\) **[\%]** \\ \hline
0 & 1.21 \(\pm\) 0.11 & 0.65 \(\pm\) 0.05 & 19.40 \(\pm\) 0.84 & 23.05 \(\pm\) 2.68 & 30.71 \(\pm\) 0.72 & 45.16 \(\pm\) 2.73 & 7.19 \(\pm\) 0.60 & 12.1 \(\pm\) 0.43 \\
6 & 0.86 \(\pm\) 0.05 & 0.55 \(\pm\) 0.06 & 10.72 \(\pm\) 1.24 & 16.19 \(\pm\) 2.43 & 19.48 \(\pm\) 2.25 & 28.66 \(\pm\) 2.74 & 6.60 \(\pm\) 0.59 & 8.90 \(\pm\) 0.51 \\
10 & 0.79 \(\pm\) 0.07 & 0.39 \(\pm\) 0.21 & 8.75 \(\pm\) 0.94 & 13.14 \(\pm\) 1.96 & 13.21 \(\pm\) 0.99 & 20.78 \(\pm\) 2.29 & 4.11 \(\pm\) 0.70 & 8.41 \(\pm\) 0.14 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mechanical characterization results: elastic modulus (\(E_{T}\) and \(E_{F}\)), yield stress (\(\sigma_{T,Y}\) and \(\sigma_{F,Y}\)), ultimate tensile strength (\(UTS\)), ultimate flexural strength (\(UTS\)), and elongation at break (\(\epsilon_{T,R}\) and \(\epsilon_{F,R}\)). \(T\) indicates tensile, while \(F\) indicates flexural. The \(\pm\) symbol indicates the standard deviation. polarity, promoting better interactions with the polyamide [69]. The establishment of a uniform and homogeneous incorporation of the nanofillers within the polymeric matrix is therefore essential to ensure the development of composite materials for laser sintering with improved properties. The results suggest that the xGNPs may not have been properly dispersed and distributed within the nylon matrix, thus requiring further investigation to better understand the interaction between the two constituents both in terms of mixture preparation and process parameter combination.