## 3 Result and Discussion
### Mechanical Properties
#### 3.3.3. Effect of NaOH Concentration  
NaOH processing, also known as merecization, is a common form of pre-treatment for organic textiles. Due to the apparent alkali treatment, the price of lignocellulosic materials is rising compared to crystal cellulose. The hydroxyl group in the framework was eliminated due to this procedure. In NaOH circumstances, the composite showed a positive outcome in all categories [40]. The mean values of tension, bending, and impact behaviour of sisal/flax-based hybrid composites are shown in Figure 12. Figure 12 shows that the most excellent tensile, flexural, and impact strength values were 59.94 MPa, 149.52 MPa, and 37.9 KJ/m\({}^{2}\) at 5% NaOH. Eliminating impurities from the fibre's surface was not as good at lesser NaOH concentrations (1 and 3 wt.%), resulting in weak fibre binding with matrices. The 5% NaOH pre-treatment with 4 h of alkali increased exterior adhesion by eradicating natural and other foams, resulting in a difficult topography as  
Figure 10: The average values of mechanical strength based on nano Al\({}_{2}\)O\({}_{3}\) particles. pect of the surface. Sisal and flax fibres were chemically pre-treated with a 5% sodium hydroxide (NaOH) preparation for 4 h to remove hydrophilic hydroxyl collections and impurities from roughage fibres. Even with the matrix material, this will improve fibre interactions and durability [41]. This enhances the mechanical and microstructural characterization through growing polymerisation stages and fibres' crystal structures. Figure 13 shows the mean impact strength values of sisal/flax hybrid composites based on various input parameters. Figure 11: Mean Values of Bending Behaviour of Hybrid Composites with various input parameters. Figure 12: The average values of mechanical strength based on NaOH concentrations. After NaOH treatment, the fibres were extensively rinsed with fresh and deionized water to eliminate the tiny amounts of NaOH. The XRD scans showed no indication of a greater NaOH concentration in the fibre. Except for peaks at 115, 119, and 215, the remaining peaks demonstrated the NaOH presentation in the fibre mat. Only at greater concentrations (5 wt.%) of NaOH processes is sodium aluminate formed. The content of NaOH in such samples appears to be a factor in the production of sodium aluminate from the residual. This shows that greater NaOH levels combined with extremely high temperatures promote the synthesis of aluminate, the substrate for sodium hydroxide nanoparticles [42]. The XRD data show that the concentration of HCl did not affect the procedure. Previous research has found that the proton content highly influences the leaching rate at the start of the reaction in the anion of the oxide (CI). Larger HCl levels result in much less acid ionization, which reduces the extraction rate and processing efficiency because a rise in titratable acidity raises the number of metallic ions in the solutions. The formation of sodium aluminate is expressed in Equation (6)  
\[\text{Al}_{2}\text{O}_{3}+2\text{ NaOH}\to 2\text{NaAl}_{2}\text{O}_{3}+\text{H}_{2}\text{O} \tag{6}\]  
Figure 14a-d show SEM images of plain epoxy, untreated, and various % alkaline-treated fibre-reinforced composites after tensile behaviour, which may be used to measure the degree of adhesive quality between the fibre reinforcement and the polymer matrices. When opposed to alkaline-treated fibres, untreated fibres exhibit more holes and voids. The discrepancy in bonding among organic compounds and the adherence of fibres in a specific location caused these voids to emerge. These spaces are minimised in treated fibres due to the alkaline solution reacting with the fibres, resulting in the creation of acetic cellulose and the insemination of hydroxide deposits, both of which modify the fibres' binding properties [43]. Figure 14a shows the microstructural image of plain epoxy resin. Figure 14b-e show the microstructural images of 0 wt.%, 1 wt.%, 3 wt.%, and 5 wt.% concentrations of NaOH pre-treated fibre-based composites.