## 3 Results and Discussions
### Mechanical Properties Analysis of Specimens Fabricated with FDM
Therefore, during this FDM process, plastic melts between two scan lines or two layers enabled an improved fusion and adhesion, so that more energy was needed to resist the mechanical force. In general, the overall mechanical performance of PLA/untreated WSP was improved through NaOH/KH550 treatment and was optimized at 8 wt.% KH550. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & **Tensile** & **Tensile** & **Flexural** & **Flexural** & **Compressive** & **Compressive** \\  & **Strength** & **Modulus** & **Strength** & **Modulus** & **Strength** & **Modulus** \\  & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** \\ \hline pure PLA & 57.3 \(\pm\) 1.0 & 1908.7 \(\pm\) 9.4 & 69.0 \(\pm\) 1.1 & 35.8 \(\pm\) 1.2 & 526.9 \(\pm\) 3.6 & 65.9 \(\pm\) 0.9 \\ PLA/untreated WSP & 48.3 \(\pm\) 0.5 & 3050.4 \(\pm\) 25.1 & 44.1 \(\pm\) 0.6 & 33.5 \(\pm\) 2.5 & 212.1 \(\pm\) 1.5 & 26.5 \(\pm\) 0.5 \\ PLA/2\%NaSi treated WSP & 49.6 \(\pm\) 1.2 & 2284.5 \(\pm\) 5.25 & 47.1 \(\pm\) 0.6 & 32.3 \(\pm\) 0.8 & 219.9 \(\pm\) 1.3 & 27.5 \(\pm\) 0.2 \\ PLA/4\%NaSi treated WSP & 50.8 \(\pm\) 1.2 & 2442.7 \(\pm\) 16 & 49.9 \(\pm\) 0.8 & 32.1 \(\pm\) 0.9 & 252.5 \(\pm\) 2.1 & 31.6 \(\pm\) 0.3 \\ PLA/6\%NaSi treated WSP & 50.3 \(\pm\) 0.1 & 2381.5 \(\pm\) 15.7 & 51.2 \(\pm\) 0.9 & 31.17 \(\pm\) 1.07 & 266.82 \(\pm\) 1.22 & 33.35 \(\pm\) 0.15 \\ PLA/8\%NaSi treated WSP & 52.5 \(\pm\) 0.7 & 2570.5 \(\pm\) 22.8 & 51.7 \(\pm\) 2.8 & 28.8 \(\pm\) 3.1 & 276.6 \(\pm\) 2.9 & 34.6 \(\pm\) 0.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The mechanical properties of Fused Deposition Modeling (FDM) PLA, untreated, and treated Poly (lactic acid)/Walnut shell powder (PLA/WSP) biocomposite samples. .4.2 The Effect of WSP Weight Ratio on the Mechanical Properties of FDM PLA/WSP Biocomposite Samples  
The mechanical properties of FDM PLA biocomposites with WSP treated with 8 wt.% concentration of silane are better than that of treated with other concentration of silane. Therefore, the PLA/8%NaSi treated WSP bioccomposite filament was chosen to develop farther experiments. Table 2 gives the tensile properties of the FDM samples of PLA biocomposites with 5-15 wt.% WSP treated with 8 wt.% concentration of silane. When increasing the ratio of WSP, the tensile strength of biocomposite samples was improved from 52.5 MPa to 56.2 MPa at 10 wt.% WSP, followed by a moderate drop to 55.3 MPa at 15 wt.% WSP. The silane coupled reaction with both PLA and WSP resulted in a high interfacial bonding [48]. The good interfacial compatibility was beneficial to transfer stress in the tensile test. The result is similar to that in references for PLA/corn fibers composites [48] and Polypropylene/Argan nut shells composites [50]. The tensile modulus dropped down by 19.1% to 2080.5 MPa at 10 wt.% WSP and increases a little to 2177.9 MPa at 15 wt.% WSP, which indicates that the anti-deformation capability was higher for a higher ratio of WSP. The improvement showed that a higher ratio of WSP was beneficial to improve the mechanical properties of the FDM PLA/WSP biocomposite samples. The biocompatible filaments have the potential to be used as cheaper FDM materials than the PLA filaments. The performance of the tensile modulus was similar to that in the research of the PLA/coir fiber composites [45].