## 3 Results
### Optimization of Plasma Treatment Parameters  
A least squares analysis was used to establish a model based on the observation of 22 results from the full factorial experiments. The HF\({}_{\rm tr}\)RE composite sample's tensile strength, which was impacted by the two factors, was the response variable under investigation. The equation for a second-order polynomial that was produced from the experimental data using quadratic regression models incorporated these factors. The prop  
Figure 8: (**a**) Tensile strength and elongation at break and (**b**) calculated energy absorption of the epoxy, the epoxy composite reinforced with untreated HF (HFRE), and the epoxy composite reinforced with plasma-treated HF (HF\({}_{\rm tr}\)RE) in various gasses. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Energy** & **Elongation at** & **Tensile Strength** & **Increase Rate of** \\  & **Absorption** & **Break** & **(MPa)** & **Tensile Value** \\  & **(MPa mm/mm)** & **(\%)** & **(\%)** & **(\%)** \\ \hline Epoxy & 101.93 \(\pm\) 6.68 \({}^{\rm c}\) & 5.54 \(\pm\) 0.31 \({}^{\rm ab}\) & 39.13 \(\pm\) 0.29 \({}^{\rm e}\) & - \\ HFRE & 116.01 \(\pm\) 8.83 \({}^{\rm abc}\) & 6.27 \(\pm\) 0.41 \({}^{\rm ab}\) & 40.39 \(\pm\) 0.52 \({}^{\rm d}\) & - \\ (Ar)HF\({}_{\rm tr}\)RE & 124.01 \(\pm\) 5.72 \({}^{\rm ab}\) & 5.24 \(\pm\) 0.16 \({}^{\rm bc}\) & 44.77 \(\pm\) 0.35 \({}^{\rm b}\) & 10.8 \\ (Ar+N\({}_{2}\))HF\({}_{\rm tr}\)RE & 121.32 \(\pm\) 2.62 \({}^{\rm b}\) & 6.09 \(\pm\) 0.46 \({}^{\rm ab}\) & 43.11 \(\pm\) 0.71 \({}^{\rm bc}\) & 6.7 \\ (Ar+O\({}_{2}\))HF\({}_{\rm tr}\)RE & 130.64 \(\pm\) 5.40 \({}^{\rm ab}\) & 5.69 \(\pm\) 0.29 \({}^{\rm ab}\) & 46.52 \(\pm\) 0.54 \({}^{\rm a}\) & 15.2 \\ \hline \hline \end{tabular} Values in the same column with the same letters are not significantly different at \(p\leq\) 0.05.  
\end{table} 
Table 3: Mechanical properties of the HFRE and HF\({}_{\rm tr}\)RE composite samples. erties of the epoxy composite reinforced with O2 plasma-treated HF are comprehensively presented in Table 4, which also highlights the results related to the two variables under investigation and the sample strength. The response surface methodology (RSM) was utilized to optimize the plasma treatment parameters, specifically treatment time and discharge power, with the objective of maximizing the tensile strength of the (Ar+O2)HFtrRE composites. The analysis of variance (ANOVA) results (Table 5) indicated that the quadratic model was significant (\(p<0.05\)), with a coefficient of determination (R-aq) of 44.28%, suggesting a moderate fit between the experimental data and the model. \[ \begin{array}{l}\text{Tensile Strength}=42.2-0.004\text{ Power}-0.820\text{ Treatment time}+0.00480\\ \text{Power}^{\star}\text{Treatment time}+3.58\text{CtPtr}\end{array}  \tag{2}\] \begin{table}
\begin{tabular}{c c c c c c} \hline
**Run** & **Center** & **Blocks** & **Power** & **Treatment Time** & **Tensile** \\
**Order** & **Point** & & **(W)** & **(min)** & **Strength (MPa)** \\ \hline  
\hline \end{tabular}
\end{table} 
Table 4: Experimental results based on the DOE method. \begin{table}
\begin{tabular}{l c c c c} \hline
**Source** & **DF** & **Adj. SS** & **Adj. Ms** & **F-Value** & **\(p\)-Value** \\ \hline Model & 4 & 222.09 & 55.52 & 3.38 & 0.033 \\ Linear & 2 & 107.77 & 53.88 & 3.28 & 0.063 \\ Power & 1 & 94.81 & 94.81 & 5.77 & 0.028 \\ Treatment time & 1 & 12.96 & 12.96 & 0.79 & 0.387 \\
2-Way Interactions & 1 & 44.28 & 44.28 & 2.69 & 0.119 \\ Power*Treatment time & 1 & 44.28 & 44.28 & 2.69 & 0.119 \\ Curvature & 1 & 70.04 & 70.04 & 4.26 & 0.055 \\ Error & 17 & 279.47 & 16.44 & & \\ Total & 21 & 501.56 & & & \\ Model Summary & & & & & \\ \(S\) & \(R\)-aq. & \(R\)-aq. (adj.) & \(R\)-aq. (pred.) & & \\
4.05455 & 44.28\% & 31.17\% & 0.00\% & & \\ \hline \end{tabular}
\end{table} 
Table 5: Analysis of variance of tensile strength of HFtrRE composite sample.