Experimental Investigation of High Filler Loading of SiO2 on the Mechanical and Dynamic Mechanical Analysis of Natural PALF fibre-Based Hybrid Composite

This work aims to investigate the effect of high filler loadings of SiO2 nanoparticles on the mechanical properties of pineapple leaf fiber (PALF) epoxy hybrid composites. The compression molding process was used to create the composite. To achieve the aforementioned goals, the blends were made using 25% PALF and varied weight proportions (3 wt%, 6 wt%, and 9 wt%) of SiO2 nanoparticles. Tensile, bending, impact, interlaminar shear, shoreline D hardness, and dynamic mechanical analysis were all evaluated. SEM was used to examine the morphology of the materials, and an FTIR spectrometer was used to look for the presence of organic chemicals in fiber-reinforced composite materials. The findings show that adding 25% PALF fiber and 6% SiO2 nanoparticles (D-type) to the epoxy polymer improved the thermal and mechanical properties of the composites. Even the high filler content of SiO2 (E-type) reveals the highest mechanical strength compared to the A and B types. It can be attributed to the improved interaction and homogeneous dispersion of the fillers and epoxy polymers. Moreover, the water uptake parameters of all samples were studied. The findings showed that the inclusion of reinforcements boosts the water uptake of the composite significantly. The initial deterioration rate of the SiO2-incorporated hybrids is almost the same, at about 400 °C, which is considerably greater than that of the beginning breakdown temperatures of PALF (300 °C), according to the thermography results. Due to that, the inorganic SiO2-filled PALF-reinforced polymer composites have increased degradability and generate less environmental pollution, and these biocomposites have demonstrated application in the construction, packaging, furnishings, automobile, and biotechnological domains.


Introduction
In the current context, there is a growing desire for innovative composite materials with increased properties to meet distinct performance needs. The general approach for developing substances is the introduction of fillers and fiber reinforcements to plastics. Polymers have expanded their possible applications in so many organizations due to their high resistance to corrosion, low price, and lightweight [1]. Most plastics are made with petrochemicals obtained from fossil fuels. Global plastic usage was estimated at USD 568.9 billion in 2021 and is predicted to rise at a 3.2% yearly rate for the following seven years. Although plastic items are affordable and have attractive long-lasting features, they are not biodegradable and collect as garbage in landfills and seas once their useful life is through. According to environmental scientists, by 2050, there will be around 12,000 million tonnes of plastic trash in landfills globally. It is estimated that 400 million tonnes of plastic garbage are created each year, with packaging accounting for about half of this total. Of the estimated 400 million tonnes, around 150 million tonnes end up in the world's seas [2,3]. As a result, it is critical to choose sustainable raw materials 1 3 that are recyclable, compostable, and environmentally friendly. As a result, ecologically friendly alternatives such as biocomposites have been developed. Biocomposites are a prominent research field due to their remarkable features like as renewability, degradability, toughness, lightweight, and cost-effectiveness. Biomaterials are often composed of bio-based polymers as well as organic fibers obtained from sustainable natural materials that may be utilized to completely replace non-renewable plastics. Furthermore, because of their minimal environmental impacts, biocomposites are preferable for people as well as other life forms. Bio-based composite consumption is predicted to expand at a compounded yearly growth rate of 11.2% between 2017 and 2023. To this research, the global biocomposites business will have a sizable industry [4,5].
Natural fiber generated from animals or plants is the most effective reinforcing material for composite. Fibres made from different sections of plants, like wood, coco fibre, cannabis, sisal, pineapple, flaxseed, banana fibre, jute, papaya leaf, as well as ramie, can be used as reinforcement material in polymers [6]. Of all regularly utilized biological fibers, pineapple leaf (PALF) fibers possess the greatest promise for usage as reinforcing in fiber or powdered format to create a high-tensile, inexpensive, and recyclable biocompatible product. PALF fibers are multilayer fibers derived from pineapple leaves [7]. PALF fibers are preferred over other natural fabrics due to their high cellulose content (70-85%), which leads to higher bending and tensile qualities than flaxseed, jute, sisal, and wool fibers. PALF has similar bending and twisting stiffness to jute fiber. PALF is widely available, has a low density, a good aspect ratio, as well as a small microfibrillar inclination [8]. Mohanty et al. [9] observed that PALF does have a high modulus and has a great potential for usage in the chemical industries. According to Thanawan et al., [10] the exposure to 30 phr PALF raised the compressive and tearing strengths of NBR laminate to 15 psi and 200 kN/mm, respectively. According to Amornsakchai et al. [11] the PALF may be efficiently employed in a polypropylene matrix. Despite a wide range of favorable qualities, PALF has lower impact strength than rice husk. To increase their qualities holistically, PALF as well as other fibers or fillers must be reinforced within a single polymer matrix. The combination of a rigid and moderately elastic fiber with an extreme load-to-failure fiber increases the fracture toughness of the resultant composite [12]. Furthermore, combining one kind of organic fiber with the other gives a noteworthy and workable option that leads to multipurpose composites having great creep and wear strength and better impact strength [13]. Several prior studies [9,14,15] have been undertaken on the PALF fibre and filler individually to determine their distinct physical, mechanical, and thermal properties, but the combination of PALF fibre and filler has yet to be investigated. Several research projects have found that incorporating filler or micro-or nanoparticles at varying weight percentages into composites improves their physiological, structural, and temperature characteristics for diverse economic and constructive loading conditions [16]. The goal of the hybrid biocomposites constructed from organic fibre and filler was to achieve the cumulative influence of their varied features, including flawless insulation, dimensional consistency, improved interfacial adhesion, higher mechanical and impact strength, modified elasticity, and non-corrosiveness. PALF and fillers are the greatest examples of low-cost, lighter-weight biocomposites components for architectural and industrial applications [17].
For instance, polymers with silicon dioxide (SiO 2 ) nanoparticles have outstanding physical, thermodynamic, as well as other characteristics. It should be noted that SiO 2 nanoparticles are currently being investigated as potential replacements in polymeric matrices. Le et al. [18] conducted tensile and fracturing experiments using scattered silicon in an epoxy coating, finding that the inclusion of 5% nanofillers might increase rigidity and breakage energies. Nano-SiO 2 is an ecologically friendly product with a composition comparable to basalt fiber. Due to its rich content, excellent efficiency, extensive surface area, tiny sizes, and high adsorption, it is extensively used in coatings, polymers, and chemicals, as well as other industries. Liu et al. [19] covered sandblasting iron using composite material made of microand nano-SiO 2 particles as well as an epoxy polymeric foundation, accordingly. In a saline spraying test, the composites were weathered. According to studies, nano-SiO 2 coatings are more corrosion-resistant than micro-SiO 2 coatings [20]. When compared to conventional epoxy coating, the impact resistance of hardened epoxy coating increased from 0.71 MPa to 0.93 MPa, a 20.2% rise, as well as the glass transition point from 200 ºC to 158 ºC, implying that nano-SiO 2 incorporation dramatically improved the damage tolerance and elevated heat resistance of the epoxy coating [21].
Several researchers have treated the surfaces of fibers with nano-SiO 2 . Wang et al. [22] used a sol-gel approach to transplant a SiO 2 covering with such a nano porosity architecture on the surfaces of PBO fibers. The adhesion strength among the altered PBO/SiO 2 fiber and epoxy was discovered to be dramatically improved, the interface's shear force rose by 123.25%, and the hydrophobic nature also was highly improved. Li et al. [23] created an aramid fiber insulation sheet by processing this with 1 wt. % of SiO 2 . Both mechanical and electrical testing was performed on the aramid fiber insulation sheet before and following modifications. A significant interfacial impact between nano-SiO 2 and synthetic fibers was discovered, resulting in a 1% improvement in tensile strength, deformation at breaking, and dielectric breakdown power [24]. As contrasted to untreated aramid insulation sheets, SiO 2 -modified aramid fiber insulation paper improved by 7.5%, 10%, and 14%, 1 3 respectively. The physical and dielectric characteristics of a carbon fiber insulation sheet were enhanced as a result. Cheng et al. found that increasing the silica concentration improved the compression strength of glass-epoxy hybrids [25]. The improved strength of concrete might be ascribed to improved interfacial adhesion caused by the scattered silica nanoparticles.
Admittedly, few research projects have focused on the effect of laminate architectures as well as the role of inorganic nanoparticles such as SiO 2 particles on the characteristics of PALF composite materials based on epoxy. The purpose of this work was to establish the possibility of producing PALF/SiO 2 -based hybrid materials with varying filler weight proportions. To achieve the aforementioned goals, the mechanical and dynamic mechanical characteristics of the composites were investigated.

Materials
In this investigation, artificial epoxy resin 128 grade, as well as curing agent H-1312, were obtained from the C.K. pharmaceutical sector and employed as polymer matrices. Just 52% of each pineapple fruit is used for jam and juice manufacture. The remaining 48% is made up of discarded fruit peel and leaves. These wastes are high in lignin and cellulose, making them excellent raw materials for related fibers. It contributes to zero waste management and pollution prevention in the ecosystem. Simultaneously, the PALF fiber serves as the primary load-carrying member in composites. It also increases the materials' strength and stiffness.
Because of their numerous advantages over equivalent micro-fillers, nanoparticles have been widely employed as reinforcements or fillers in polymer matrix composites. SiO 2 is one of the most appealing nanoparticles due to its low cost, nontoxicity, biocompatibility, excellent heat resistance, and, most importantly, its ability to enhance the mechanical characteristics of the polymer matrix. In light of this, the PALF fiber was chosen as a reinforcement and nano SiO 2 as filler for the current study [26]. PALF fibers acquired at Salam, Tamil Nadu, India, were used as reinforcing material in the production of synthetic epoxy composites. In this study, synthetic fillers such as SiO 2 (10 nm in particle size) were used. Before using the PALF fiber its thoroughly washed with clean water and then treated with alkaline and silane solutions to enhance the interfacial bonding.

Fabrication of Composite Laminate
The purchased PALF fibers were cleansed with running, pure tap water to wash away dirt and other foreign elements before being dried in the sunlight for 70 h to eliminate any remaining wetness. The PALF fibers are chopped into little pieces and fed into standard slicing milling equipment to generate micro-particles of PALF fibers, which are then sieved through a 250-mesh screen. To use an electronic weight device, the epoxy polymers, curing agent, and reinforcing components were accurately weighed in varied weight proportions. The weight percentage for the manufacture of epoxy composite samples from PALF fiber and SiO 2 nanoparticles is shown in Table 1. Mechanical stirring was utilized to achieve homogeneous particulate distribution inside the resin. To prevent sudden drying, the combined liquid was promptly transferred to the mold and permitted to drain for real curing. To lower the interior water content, the created sample was poured into the mold and transported to the burner, which was set to 70 °C (after drying) [27]. Figure 1 depicts schematic representations of the fabricated composite process.

FTIR Characterization
The alterations in the functional group caused by the nanofiller's (SiO 2 ) inclusion were identified using Fourier-transform infrared spectroscopy. This technique is carried out in the 500-4000 cm-1 range, with a resolution of 2 cm −1 . The pineapple leaf particle was combined in a 1:200 ratio with potassium bromide (by weight). The mixture was then crushed in a compression die to create a thin pellet for testing [17]. At SRM University in Chennai, Tamil Nadu, India, the complete procedure was carried out utilizing IRTracer 100 Shimadzu FTIR equipment. The same was incorporated into the revised manuscript.

Mechanical Characterization
Tensile testing was carried out to measure the tensile strength of a manufactured epoxy-based polymeric hybrid composite. By the ASTM D 3039 standards, the sample was made into a rectangle with measurements of 25 mm in width, 250 mm in length, and 3 mm in thickness. This study was carried out at a crosshead velocity of 1 mm/min until the breakage was achieved [28]. The three-point bending specimen was generated in Comtech's universal tester by the ASTM D790 standards for three-point bending tests. The deformation of an epoxy-based hybrid composite during compressive stresses was determined until the sample broke or cracked. All experimental materials had their bending movement and loading evaluated by the apparatus. The dimensions of the reinforced epoxy laminate sample for this study are 12.7 mm wide, 128 mm long, and 3 mm thick. The ASTM D2344-84 standards were employed to evaluate the fracture characteristics of polymers using interlaminar testing. Sections of epoxy composite samples were cut at 18 mm in length, 6 mm in width, and 3 mm in thickness. The assessment includes a spanning length of thirty mm and a speed of one millimeter per minute [29,30]. The fracture toughness of epoxy polymeric composites is defined as their ability to absorb power from such an impact force in the context of a smooth surface that centers on strains. The izod impact test was carried out by the ASTM D 256 standards. Deformation durability testing equipment was used to assess the Shore D hardness of epoxy polymeric composites. An indenter was pushed against the reinforced hybrid composite sample until the bottom section of the indenter made total contact with the lamination. The polymeric characteristics can affect' hardness, which is indicated using the hardness indenter.
The experiment was carried out at three different spots on the lamination, and the mean toughness was computed [24].

Thermal Stability
TGA testing was performed on epoxy hybrid composites in a nitrogen environment at temperatures ranging from 30 to 800 ºC. Utilizing derivative thermal images, weight loss was evaluated, and leftover charcoal concentration was investigated at 700 ºC. The scanning electron microscopy technique was used to examine the surface structure of a hybrid composite. Before this, all of the specimens were covered with auricular dust. The hybridization interaction among the PALF fiber matrix and SiO 2 nanoparticles was shown using Fourier transform infrared spectroscopy.

Moisture Absorption
The water uptake research for epoxy composite materials was performed by the ASTM D 570 specification. The specimen was dried in a furnace for a specific period at a specific temperature (60ºC), and its original weight was determined. The resulting epoxy-hybrid materials were then submerged in water for 60 days at ambient temperature. Following immersion, specimens were retrieved, extra water was wiped away using a towel, and they were measured again. The difference in weights between the beginning and final weights was recorded [31].

FTIR Characterization
The existence of organic compounds in fiber-reinforced epoxy composites was investigated using an FTIR spectrometer. The substituents of a composite's constituents were determined using FTIR. This substituent was identified using the FTIR attenuated whole reflection (ATR) equipment. The wavelength spectrum of the equipment was 500-4000 cm-1.
The transparency setting was used to capture the FTIR spectrum. Figure 2 depicts the FTIR spectroscopy of the PALF composite. An O-H group's feature was noticeable among the intensities of 3200 and 3550 cm-1. Peaks for C-H extending and C = O extending are located at 2801-2850 cm-1 and 1601-1650 cm-1, respectively. The wavelength region 1200-1300 cm-1 in Fig. 2 reveals C-H binding. The spectral analysis of PALF fiber had changed following hybridization with SiO 2 nanoparticles. The bending vibration of N-H groupings around 2800 cm-1 was widened, perhaps due to interactions of hydrogen bonds among SiO 2 nanoparticles and PALF fiber [32]. Trend shifts from 1793 to 1798 cm-1 as well as 3640 to 3680 cm-1, correspondingly, guarantee the presence of the hydroxyl group among -OH and -C = O.
The vibrating wavelength of Si-OH changes from 3923 to 3969 cm-1, indicating the presence of silicon in the epoxy. It was possible to determine that there were substantial contacts between the SiO 2 nanoparticles and the PALF fiber. So, these contacts might be diverse, including the previously stated hydrogen atoms and cytotoxic processes, in addition to electrostatic attraction among SiO 2 nanoparticles and PALF fiber [33]. Figure 3 shows the tensile strength and modulus of PALF/ SiO2-based hybrid composites. From the tensile curve, it concluded that lower content of filler exhibits high strength.

Tensile Behavior
The mentioned comment has been in favour of D-type specimens. It was anticipated that combining a 6 wt.% SiO 2 composite with natural fiber would improve the mechanical characteristics of hybrid composites. As shown in Fig. 3 Moreover, the high adhesiveness of the alkali-silanemodified PALF fiber as well as the epoxy composite results in excellent binding at its contact point. Esters, hydrophobic interactions, and copolymer (NH-CO) production might occur during the metaphase between the PALF fiber and the basic matrices. Its collective effects of the nano-SiO 2 fillers and processed PALF fiber guarantee that the combination has good strength. As a result, for the previously indicated scenario, significant hybridization is being found [21,35].
The tensile strength of the composites decreased as the SiO 2 concentration increased (over 6 wt.%). This is really due to the build-up of filler particles in the epoxy. This might be because SiO 2 nanoparticles accumulated on the fiber surface and caused numerous flaws, like fractures. Once the tension load was applied to the fiber, the fractures spread widely and spread from the handling to the fiber surface, leading to several maximum stress points on that surface and speeding fiber breakage [36]. Figure 4   Tensile stress-strain graphs show that when the nanofiller concentration grows from 3 to 9%, the strain percentage steadily drops, indicating that the composite's brittleness increases. This reduction in strain can be due to the nanofillers restricting the mobility of molecular chains, resulting in enhanced tensile characteristics. Moreover, none of the samples failed abruptly but instead displayed pseudoplastic behavior before reaching the final tensile stress value [26]. Figure 5 depicts the flexural behavior of epoxy as well as allhybrid composites. Surprisingly, all of the materials show the same trend for bending modulus and strength as they do for tension characteristics. Figure 6 shows the stress-strain curve of the bending behaviour of PALF/SiO2-based hybrid composites. Flexural characteristics of PALF/SiO 2 -derived hybrid materials C, D, and E are greatly enhanced as compared to regular epoxy. The bending strengths rose by 30%, 42%, and 45% in bio-composites such as C-type, D-type, and E-type, respectively. This increase was caused by the efficient load transfer across matrices to reinforcements as a consequence of the strong esters, hydroxyls, and nylon binding interactions among PALF fiber and resin, as well as the good distribution of nanocrystalline silicon dioxide. It had also been predicted that nano SiO 2 would have minimized the gap between the strengthening PALF fiber and matrix. This finding is in contrast with Hamid et al. [37]. The E-type of all materials had the maximum flexural strength (58.96 MPa) and elasticity (2.79 GPa), whereas the A-type had the least strength properties at 26.32 MPa and an elasticity of 0.85 GPA. Tensile property trends were also detected for flexural characteristics, indicating a favorable hybridized impact. A high adhesion/interaction between the PALF fiber and epoxy contact, as well as the addition of nanocrystalline SiO 2 , results in improved load transmission. Furthermore, as previously reported, superior SiO 2 dispersal and distance decrease among PALF fiber and epoxy matrices contacts should have had an important impact in boosting load transmission from matrices to PALF fiber [10]. Flexural stress-strain graphs show that when the nanofiller concentration was increased from 3 to 9%, the strain percentage steadily drops, indicating that the composite's ductility reduces. Because of the presence of extra stiff nanofillers, which perturb the deformation of the crystalline area in the matrix, this is related to decreased chain mobility and matrix deformability, resulting in enhanced bending characteristics. Moreover, none of the samples failed abruptly but instead displayed pseudo-plastic characteristics before reaching the final flexural stress value. Flexural strength exhibits a comparable pattern to tensile, however, it varies less across formulations [26].

Interlaminar Shear Strength
For instance, the interlaminar shear of an elastomeric polymeric matrix is vulnerable to the formation of voids and interfacial adhesion between the filler and the polymers. The produced composites were tested for resistance

Impact and Hardness Properties
An automated Izod impact tester was used to measure the fracture toughness of epoxy composite samples. Figure 8 depicts the fracture toughness of epoxy polymer hybrid composites as a function of the presence of SiO 2 nanoparticles. Figure 8 shows that the fracture toughness of the D and E-type composites has increased and reached the highest level of 6.32 and 5.24 kJ/m 2 , respectively, which would be higher than the A, B, and C-type composites. The impact resistance of the polymer binder has also been determined to match the stiffness of the polymer system. The inclusion of 6% SiO 2 nanoparticles increased the stiffness of the epoxy-reinforced hybrid because SiO 2 connects several different epoxy networks via -COOH and -OH structural features. Additionally, the inclusion of filler particles reduces the fracture toughness of the epoxy-reinforced hybrid by increasing the filler particle concentration [41]. The fortification from pressing in the sample is referred to as the characteristic Shore D toughness. The shoreline D hardness values of the produced epoxy composite samples are shown in Fig. 8. This specimen's Shore D toughness is mostly determined by stiffness. In this study, both the outer and interior sections of the SiO 2 sample were made of PALF fiber, and the SiO 2 nanoparticles became tougher. In comparison to hybrid composites, sample D does have the maximum value of Shore D toughness of 73.21, and similar findings were also investigated by Bharath et al. In comparison to hybrid composites, sample B (without filler) does have a smaller value of Shore D toughness at 41.36 owing to the decreased rigidity of PALF fabric.

Microstructural Analysis
The surface morphology of A, B, C, D, and E-type blends is shown in Fig. 9. The PALF was strongly linked with the polymers in the PALF-reinforced epoxy ( Fig. 9 (a)), as well as the rupture that developed throughout the fibers. This might be owing to the fundamental features of moisture absorption. Since PALF includes around 70% cellulose. Figure 9 (b) shows the SEM characterization of the composite's D-type fractured tension reinforcement. PALF fibers and nanocrystalline SiO 2 have been thoroughly entrenched in the epoxy, and the fibers have been coated and moistened with polymer. There aren't any visible cavities or gaps among the basic matrix and fiber. The direction of fibers within the matrices is crucial, as they seem to be dispersed equally at all four edges of the matrices [29]. Effective binding at the intersection of PALF fiber, SiO 2 , and epoxy matrices results in excellent fiber and polymeric contact. The surface morphology was also found to be rough, with branching, bending cracking, and cracked locking. These properties were also investigated in the particulate epoxy sphere. The failure mode of the 9 wt.% SiO 2 and 25% PALF-reinforced epoxy polymers appeared coarse, and more particles appeared to have deboned from the polymers, as seen by the voids surrounding the fillers. Figure 9 (c) also showed the existence of a basis for filler to accumulate. The concentration of SiO 2 nanoparticles acted as a carrier of failures, potentially reducing the material properties even more [42].  Figure 10 illustrates the DMA curves of PALF materials and SiO 2 -based hybrid materials. Figure 10 also explains the storage modulus profiles of materials with a different weight proportion of SiO 2 filer. The maximum storage modulus at 30 ºC is 6 wt.% SiO 2 /PALF. This seems to be owing to the composite's higher interfacial compliance, which limits the movement of polymeric chains and leads the contact between the fibers and the matrix to transfer greater loads, raising the rigidity of a material. The higher the loss ratio, the greater the amount of energy wasted by contact between the matrix and reinforcement [43].

Loss Modulus
The proportion of loss modulus to storage modulus is equivalent to the value of the dissipation factor, which makes it an essential metric when evaluating the mechanical behavior of fiber-reinforced materials. Figure 11 depicts the tan curve of a mixture before and after alteration. The change in temperature graphs in the image demonstrates that the enhanced composite's temperature of glass transition (Tg) is generally rising. With a SiO 2 level of 6 wt%, the Tg of a hybrid increases by 20 °C to 156.6 °C when compared to the PALF material.
When the degree of polymerization changes from a glassy to a rubbery condition as the temperature increases, the polymer moves substantially higher cohesion and friction barriers, which leads to greater energy loss, a worse storage modulus, and increased failure. The contact of a SiO 2 /PALF composite with a weight of 6% has a high adhesion property, a strong capacity to control the motion of an adhesive long sequence, as well as a low coefficient of friction energy usage. As a result, its storage modulus diminishes rapidly, as does the amplitude of tan. Whenever the SiO 2 levels are excessive (9 wt%), aggregates on the fiber surface impede resin-fiber interaction, and interfacial bonding is poor, leading to greater energy dissipation [25].

Damping Factor (Tan δ)
Tan δ specified a mechanical dampening factor. The dynamic loss modulus to dynamic storage modulus ratio can be used to forecast the occurrence of molecular mobility transformations like the glass transition temperature (Tg). Whenever PALF and epoxy resin-based materials Fig. 9 Microstructural Images of a PALF; b PALF/6 wt.% of SiO 2 ; c PALF/9 wt.% of SiO 2 -based hybrid composites were examined, Tg increased from 60 ºC to 65-76 ºC, but still, no substantial change in Tg was identified across the combination. The tan delta curves for all blends are shown in Fig. 12. Because of the increased limits in the movement of the polymeric chains brought about by the presence of fillers and stiff fibres, the introduction of SiO 2 fillers lowered the tan delta signal [44].
Whenever the filler amount is low, there may be areas in the composite with a high percentage of resin (matrix) that are unaffected by fibre insertion. There was no visible trend in the glass transition temperature computed from the tan delta graph. All composite's Tg values were in the 65-77 ºC region, which was identical to the Tg for epoxy and PALFbased materials (65 ºC). As a consequence, adding SiO 2 fillers had a bigger influence on the tan delta peaks compared to the stated glass transition temperature. When the overall interface surfaces within the combination expanded, the tan delta spike in Fig. 12 decreased as the filler content increased. A prior investigation discovered that strong interface adhesion reduced molecular mobility all around the reinforcement, but decreased tan values suggested improved interactions at the matrix-fiber interface [45].

Thermogravity Analysis
TGA is commonly used to assess the thermostability of materials. As seen in Fig. 13, materials breakdown may be split into two phases: moisture and impurity breakdown (0-300 C), as well as resin condensation and degradation (300-600 ºC). Because the mass decrease induced by moisture and impurity breakdown represents around 5% of the overall mass, the temperatures equivalent to 95% of a starting weight are referred to as the original degradation temperature [46]. Because the breakdown temperatures of PALF fiber and SiO 2 are substantially greater than 600 °C, the decrease in quality materials beyond 400 °C is entirely due to resin combustion and deterioration. Figure 13 reveals that the first degradation rate of the SiO 2 -incorporated composites is nearly the same, at around 400 °C, which is significantly higher than the starting decomposition temperature of PALF (300 °C). This could indicate that the fiber and polymer get a stronger bond, which reduces the polymer's mobility and increases the mixture's thermostability. Also, the remaining weight of the composite changes drastically at 600 °C. PALF, 3 wt.% SiO 2 , 6 wt.% SiO 2 , and 9 wt.% SiO 2 had residual masses of 60%, 62%, 56%, and 50%, respectively. Since the SiO 2 concentration is insufficient to be disregarded, we assume that the majority of the remaining section is made up of PALF fiber. The PALF fiber concentration in hybrids with 3 wt.% SiO 2 and 6 wt.% SiO 2 is lower compared to PALF. The possible explanation for this could be that the SiO 2 framework includes decreased interaction deficiencies, the closely packed framework between the fiber and the epoxy allows the polymer to invade the fiber, the resin content is comparatively enhanced, as well as the fiber content is comparatively lowered, and the PALF fiber content is 9 wt.% SiO 2 , which might be attributable to aggregation on the fiber surface, but also precludes the efficient approach of fiber and matrix, culminating in so many deficiencies and holes in the specimen [18,21,35]. Figure 14 depicts the water absorption properties of PALF and PALF/SiO 2 polymer composites. It is mostly determined by Fickian diffusion. Moisture content is critical for all living things. It also becomes absorbed after 60 days. For all epoxy composite samples, both the maximal water usage and the beginning time for moisture absorption increased. Water uptake qualities of composite resin are examined using factors such as immersion time, filler-to-polymer ratio, processing technologies, filler, and matrix characteristics in a given environmental condition [47]. The hydrophilic properties of leaf fibers are mainly accountable for this moisture absorption. Moisture is mostly utilized by the additives found in polymer composites strengthened with lignocellulosic biomass, such as PALF. Because the epoxy resin is hydrophobic, its moisture consumption may be decreased. Likewise, the water uptake behavior of SiO 2 nanoparticle-loaded PALF epoxy hybrid lamination is lower than that of PALF hybrids. The SiO 2 nanocrystals reduce the vacancy fraction of the composites, resulting in a reduction in water uptake capacity [48]. Moisture resilience is improved in the altered composites.

Conclusion
PALF fiber reinforced with varied weight proportions of SiO 2 filler-based hybrid composites was fabricated in this experiment, and the composites were tested for mechanical characteristics such as tensile, bending, hardness, ILSS, impact strength, and dynamic mechanical analysis. The following conclusions were drawn from the findings: • The bending vibration of N-H groupings around 2800 cm-1 was widened, perhaps due to interactions of hydrogen bonds among SiO 2 nanoparticles and PALF fiber. Trend shifts from 1793 to 1798 cm-1 as well as 3640 to 3680 cm-1, correspondingly, guarantee the presence of the hydroxyl group among -OH and -C = O. The vibrating wavelength of Si-OH changes from 3923 to 3969 cm-1, indicating the presence of silicon in the epoxy. • Among the five different types of composites i.e. A, B, C, D, and E types, the D-type composite ( Inter-laminar shear force improved as the interaction among fillers and polymers improved. According to the SEM analysis the failure mode of the 9 wt.% SiO 2 and 25% PALFreinforced epoxy polymers appeared coarse, and more particles appeared to have deboned from the polymers, as seen by the voids surrounding the fillers. • According to TGA results the first degradation rate of the SiO 2 -incorporated composites is nearly the same, at around 400 °C, which is significantly higher than the starting decomposition temperature of PALF (300 °C). This could indicate that the fiber and polymer get a stronger bond, which reduces the polymer's mobility and increases the mixture's thermostability.