## 3 Results and Discussions  
### Lap Shear Strength (LSS)  
The values obtained after the lap shear strength test are presented in Table 3. The experiments conducted with the aluminum samples treated by PEO (01 to 17) show average  
Figure 3: FLUKE 117 True RMS thermometer with type K thermocouple on the sample to be welded. lap shear strength values ranging from 5.7 to 9.5 MPa. Considering the lap shear values, it is observed that the PEO treatment resulted in increases of 2.5 to 4.3\(\times\) compared to the set without surface treatment. This is due to the costing's morphological characteristics, such as micro-pores, protrusions, and other microstructures that appear in the oxide coating, providing a larger surface area for the sample and allowing greater interaction with the thermoplastic matrix [1; 2; 21; 26; 27; 28]. The obtained lap shear values are promising compared to other studies conducted on both metallic and polymeric materials. Table 4 presents some comparisons of lap shear values and the materials used. With the development of a statistical model, the significance of parameters (independent variables) was evaluated using analysis of variance (ANOVA). This model was adjusted by the coefficient of determination (R\({}^{2}\)), which quantitatively helps assess how much each variable influences the response variable (LSS) [1; 36; 37]. The ANOVA analysis results, using the independent variables immersion time, duty cycle, and electrolyte concentration, to the dependent variable (LSS), are presented in Table 5. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Methodology** & **MPa** & **Ref.** \\ \hline AA2024 (treated by PEO) + PEI/welding by OFW (this study) & 9.5 & - \\ AA6060-T6 + AA6060-T6/adhesive bonding & 35.9 & [1] \\ AA2024-T3 (treated by PEO) + PEI/welding by OFW & 5.2 & [21] \\ AA2024-T3 (anodized) + PEI/welding by laser YB & 16 & [29] \\ AA6082-T6 + PEI glass fiber/friction injection joining & 1.1 & [30] \\ PEI Glass fiber + PEI glass fiber/adhesive bonding & 15 & [31] \\ AA5052 (treated by PEO) + Polypropylene/friction stir spot welding & 1.4 & [32] \\ CF-PPS + CF-PPS/friction stir spot welding & 2.4 & [33] \\ Polyamide 6 + Polyamide 6/adhesive bonding & 7.5 & [34] \\ AA1100 (treated by PEO) + PEI/welding by OFW & 10.7 & [35] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Shear strength values of joints in dissimilar materials. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Std. **} & \multicolumn{3}{c}{**Coded Variable**} & \multicolumn{3}{c}{**Real Variable**} & \multirow{2}{*}{**LSS (MPa)**} \\ \cline{2-2} \cline{4-7}  & **X1** & **X2** & **X3** & **Time (s)** & **Duty (\%)** & **Conc. (g/L)** \\ \hline
00 & N/A & N/A & N/A & N/A & N/A & N/A & \(2.2\pm 1.5\) \\
01 & \(-1\) & \(-1\) & \(-1\) & 300 & 20 & 3 & \(7.6\pm 3.0\) \\
02 & \(+1\) & \(-1\) & \(-1\) & 600 & 20  
It was found that the F value (responsible for checking whether a term or the model itself is associated with the response variable) for the model was 2.03, implying that the adopted model is not significant in the response variable (LSS), and also showing that there is a 20% probability of the F value being due to noise. This study observed that the only factor significantly influencing the dependent factor is the electrolyte concentration (X3). As the \"\(p\)-value\" is less than 0.05, it indicates that this factor has a significant effect on the response variable. Furthermore, when analyzing the coefficient of determination (R\({}^{2}\)), the model explains 75.15% of the PEO + welding process variability. However, the statistical model did not demonstrate significance in explaining the variability, considering its \(p\)-value (0.200), which is greater than 0.05 [23; 29; 37]. It can be inferred that the model is not significant, due to the complex mechanisms of the PEO process added to the oxy-fuel welding process (which still requires optimization), as already presented in a previous study [35; 38].