# Importance of Fiber-/Nanofiller-Based Polymer Composites in Mechanical and Erosion Performance: A Review

Authors: R. Sundarakannan; K. Balamurugan; Y. Jyothi; V. Arumugaprabu; Thanikodi Sathish; Z. Mahmoud; El Sayed Yousef; Dadapeer Basheer; Saboor Shaik
Journal: Journal of Nanomaterials
 (2023)

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## Abstract

The addition of nanofillers in the polymer matrix composites (PMC) has shown a considerable improvement in the mechanical properties and acts as a suitable replacement material. Among the various properties, erosion studies play a key role in the establishment of new materials in engineering applications irrespective of material properties. This paper primarily focus on mechanical properties of PMC and provides a view of the erosion studies conducted on various PMC that are reinforced with natural fibers and nanofillers. The study related to natural fiber as secondary reinforcement and nanofiller as primary reinforcement is taken into consideration. The natural fibers such as sisal-, pineapple-, jute-, bamboo-, banana-based polymer composites and their improvement in mechanical properties by the addition of various fillers are compared and reported. From the survey, it was noticed that the incorporation of nanofillers with natural fiber and polymers provides an acceptable range of material behavior. Being the natural fiber and its proper surface treatment enhance erosion resistance behavior.


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## Body

## 1. Introduction

A composite is a material consisting of two phases, one continuous and another discontinuous. Generally, the continuous phase is called the matrix, and the discontinuous phase is called strengthening. In the strengthening phase, two different materials were used. In comparison with the matrix, the reinforcement material has increased strength. The reinforcement and the matrix are combined to create a new type of material called composite material [1]. In most cases, the reinforcement acts as a carrier element, transferring the strength in a specific direction while protecting against damage. Composite materials were first introduced in the early 1900s, with resins serving as a matrix and carbon fiber serving as reinforcement. Due to their small weight, fiber-reinforced composites became popular in military applications during the Second World War. Since the 1900s, pure matrix materials such as polyester epoxy and vinyl esters have been developed [2]. However, because of their low strength, reinforcement was added to enhance their mechanical characteristics. After the Second World War, many types of synthetic fibers such as carbon, aramid, and basalt were produced longer. Carbon fiber-reinforced composites, however, are widely used in a variety of applications due to their low weight. Interior and exterior design in architecture, automotive and transportation, aerospace industries, electrical industries, home appliances, sports and recreation, marine, and corrosive environments are some of the application areas of composite materials [3].Metal matrix composites, ceramic matrix composites, and polymer matrix composites are three types of composite materials that may be classified according to their matrix. Metal matrix composites are stronger than monometals. High strength and low weight are two of the most important considerations for metal matrix composites [4]. Aluminum, for example, is a great example of a metal matrix used to strengthen silicon carbide and aluminum dioxide to increase their strength. Examples of metal matrix composites are titanium and alloys, copper-based composites, superalloy composites, copper-based composites, etc. [5]. The ceramic matrix was used to increase the resistance behavior of the material. Due to its toughness, this matrix was common in high temperature applications. In alumina, silica, and zirconium matrix composites, fiber and filler material can be used as a reinforcing phase [6]. The benefits of polymer matrix composites include high resistance, low cost, and a simple production method. In many applications, these characteristics may exceed monolithic materials in terms of lightness, high resistance, and resistance to corrosion [7]. According to him, thermopolymer and thermoset matrix composites can be divided into two kinds. The basic advantage of thermopolymers is that they can be reused, unlike thermosetting polymers. The thermosetting polymer is composed of chemical reactions that turn the liquid into a solid. In this stage, the molecules were dissociated and the curing agent was used to connect the polymer chain. The accelerator and catalyst generated heat through this process, which helped solidify the matrix. The polymer matrix may not be melted at high temperatures once it has been hardened. The thermopolymer, however, melted at the time of heat application and then solidified after heat removal, due to certain examples of thermal polymers, such as polypropylene, polylactic acid, and polyethylene [8].


## 2. Background

Researchers can use the strengthening phase to enhance the resistance of their composites. To reinforce polymer composites, fibers and loads are widely used. Artificial and synthetic fibers are the two types of fibers that can be found. The synthetic fiber was created by a technology and has higher mechanical properties. However, the main disadvantage of synthetic fiber is that it is not degradable, which has implications for the environment. Synthetic fibers comprise glass, kevlar, aramide, and carbon [9]. The natural fiber was developed as an alternative to synthetic fiber to address environmental concerns. Natural fibers are produced from plants, animals, and minerals. Natural fiber offers many benefits, including availability, degradability, low cost, and ease of handling. Examples of natural fibers include kenaf, flax, hemp, jute, and sisal [10]. Alkali-treated natural fibers exhibit increased cellulose content and are used in developing high-performance polymer composites [11, 12]. In recent years, particulate or filler materials have been used in polymer composites. Alkali-treated study of fractured surfaces indicated a significant improvement in mechanical properties of the composites with jute fiber as intermittent layers, areca sheath fiber as a core layer, and glass fabrics as skin layer-reinforced epoxy composites [13]. Due to the presence of high-strength jute fibers in their intermediate layers and strong resin adherence as a result of alkali treatment, hybrid areca sheath–jute–glass composites outperformed pure jute fibers–glass textiles composite [14]. To reinforce the composite materials, the filling comes in the form of flakes or powder. Organic filling, inorganic filling, and metal filling are the three commonly used types of filling. In polymer composites, particle size has the largest impact on mechanical properties. The fillers added to the polymer matrix are micro and nano sized. Fiber and filler are both used in polymer composites at this stage, with fiber increasing strength and filler improving the module. Fiber and filler composite polymers should be correctly selected to provide higher mechanical properties than conventional materials.Silane-treated fibers show improved outcomes compared to the untreated samples by removing excess lignin, wax, and hemicellulose contents fromLeucas aspera fibers and helping to boost its bonding qualities with the matrix in composite applications [15]. The modifications of silane and NaOH to the fiber resulted in reductions in diameter of 9.17% and 17.43%, improvements in a crystalline index of 41.01% and 14.86%, improvements in thermal stability of 14.15% and 4.81%, and increases in tensile strength of 37.75% and 28.92%, according to the data. The entire investigation showed that silane treatment was superior to NaOH treatment and utilizing raw fibers for Muntingia calabura microfiber [16, 17]. In comparison to untreated and KMnO4-treated Calotropis gigantea fibers (CGF) composites, results showed that NaOH-treated CGF composites displayed improved tribological behavior [18].The 10 wt%-treatedPortunus sanguinolentus shell powder-filled jute fabrics epoxy composites outperformed the other two composites. Since these findings further increase the strength of the natural fiber composites, they might be useful in lightweight applications and will help to minimize the amount of solid waste landfills created by Portunus sanguinolentus shells after food intake [19, 20]. Due to the notable compatibility between the matrix and the fibers, hybridized composites having 40 wt% jute fiber and 10 wt% hemp fiber displayed lower amounts of void content [21]. The results of the experiments show that the presence of haritaki powder (HP) significantly affects the characteristics of Coccinia grandis fibers-reinforced composites (CGFRCs) and establish that HP may be a viable nanofiller for the majority of polymer matrix composites [22]. Three weight percentages nanoclay-filled chemically treated Coccinia indica fiber-reinforced epoxy composites exhibit better adhesion at the interface of fiber and matrix when compared to untreated epoxy composites [23, 24].The outcomes unmistakably demonstrated that the addition of eggshell nanoparticles significantly affects the thermal and morphological characteristics of hemp fiber composites that have undergone alkali treatment [25]. By altering the content (in weight percentage) of both natural fibers, it was possible to determine how Tamarindus indica L. seed powder and the hybridization of hemp and jute natural fibers affected the properties of polymer nanocomposites. Because there was noticeable compatibility between the matrix and the fibers, composites with 40 wt% JF and 10 wt% HF showed less void content [26]. The results of the experiments show that the presence of HP significantly affects the characteristics of Coccinia grandis fibers-reinforced composites (CGFRCs) and establish that HP may be a viable nanofiller for the majority of polymer matrix composites [21].


## 3. Tensile Performance of Fiber-/Filler-Based Polymer Composites

Tensile strength refers to the capability of a material to withstand loads operating in opposite directions. This test may be used to determine the capacity of the material with respect to the applied force. The stress transfer behavior of the filler–fiber matrix is largely responsible for the results of the tensile test. The interlaminar area, which controls crack initiation and propagation, determines the fiber-filled composites’ strength. Secondary reinforcements (fillers) of consistent size and shape are used to reinforce the matrix in the interlaminar area. The fillers in the composite resist the first crack, which then spreads and progresses along the contact between the matrix, fiber, and filler until fracture [25].Pineapple leaf fibers will act as lingo cellulosic fibers that are obtained and collected from plants. It looks to increase the volume of tensile strength in polymer matrix composites by up to 30%. Total deformation was also shown to increase by 10% in volume. This result shows a spectacular increase in tensile strength. The elastic modulus of pineapple leaf fibers increases as the volumetric fraction increases. It has been shown that the epoxy matrix is the best to form a composite synthetic matrix of jute fibers [10]. Two different compositions of jute fibers were created, one with two coats and the other with three coats. Obviously, as the number of layers of jute fibers increases, the tensile strength also increases. This clearly shows that the tensile strength of three layers of jute fiber composites reached a maximum of 53 MPa [11].Cementitious composites with five different polypropylene fiber assays, three different prisms, and three different cubes demonstrated improved mechanical properties [12]. The results clearly show that the fiber content does not affect the tensile strength of polypropylene-based cementitious composites. For all fiber contents, the percentage increase in fracture modulus was almost double the increase in fracture strength. The decrement in tensile property in compatible composites is due to the acrylic ester content of the compatibilizer acting as a plasticizer, as well as the enhanced strength and elongation at break of compatible PP–RH biocomposite materials compared to uncompatibilized biocomposite materials tested for the Young’s modulus [13].The tensile and bending strength of the hemp fiber biocomposite is influenced by three types of dosage on the filling material and on the fibers in the composites [27]. Hemp fiber composite may be used in the manufacture of various thermoplastics. It was also discovered that the addition of coupling agents such as MAPP resulted in a slight increase in composite tensile strength due to improved fiber-matrix interfacial adhesion. Glass fiber filled with red mud particles and jute fiber manufactured using a layup technique as hybrid epoxy composites is preferred for low-load applications [28]. The composite strength is superior to other conventional materials used for low-load applications. The tensile strength of the 3-ply composite with red mud is lower than the tensile strength of the 3-ply composite without red mud. This may be due to inadequate fiber wetting, uneven distribution of red sludge in the matrix material, or the presence of voids in the sample.Higher concentrations of nanoalumina particles and coupling agents resulted in lower tensile strength due to decreased reticulation density of the polymer [29]. The chemical treatment fiber significantly improves adhesion between matrices in sisal fiber-reinforced epoxy composites and this effect was reported through tensile strength that prevents the failure to lift in the tensile strength [30]. The coupling agent of maleic anhydride grafted polypropylene was used in an intermeshing counter-rotating twin screw extruder to test the tensile strength of bamboo and glass fibers combined with polypropylene to improve adhesion properties [31]. The results of the tensile tests show that the 15 : 15 percentage of fibers and the 2% coupling compound achieved a maximum tensile strength of 69%. The different lengths of palm kernel fibers were incorporated into the polymer matrix at different weight percentages to form a rooflite composite [32]. The variation in hybridization and fiber content showed variation in the tensile strength. Figure 1 shows the tensile test results of the composite fabricated.Figure 1
Tensile test results of fiber-/filler-reinforced polymer composites.Tensile test results of sisal–glass fiber, jute–glass fiber, and sisal–jute–glass fiber-reinforced polyester composites, the jute–glass fiber composites showed a maximum strength of around 229.54 MPa and the failure analysis through SEM confirms that fiber breakage, voids, fractured surface, and interfacial cracks [33]. The incorporation of natural fibers like banana, sisal, and jute into polymers has improved the tensile strength of composites. Surface treatment is obtained by increasing tensile strength [34].The mechanical properties of tamarinian-reinforced vinyl ester composites are better at 15% by weight and are believed to have a tensile strength of about 34.1 MPa. In addition, the tensile strength, module, impact strength, and fracture elongation of pure epoxy composites decreased from 20.5 to 25.7657 MPa [35]. The incorporation of 50% date palm filler reduces energy absorption dramatically from 50% to 32% and the SEM microstructure revealed fine interfacial bonding in 50% date palm filler epoxy composites, but increasing the date palm filler loading reduces interfacial strength due to poor wet ability [36]. The epoxy filled with 5 g of luffa cylindrical fiber-reinforced hybrid composites has higher mechanical traction properties than the epoxy filled with other fiber-reinforced composites. Notably, the epoxy (90 g) filled with 5 g of Luffa cylindrica fiber-reinforced hybrid composite significantly improved its tensile strength and tensile modulus [37]. The hybrid composites showed an increase in red mud weight percentages improves the tensile strength when the red mud with 10% and 20% demonstrated good bonding with the fiber and matrix, as evidenced by scanning electron microscopy images. Red mud-filled composites were found to be a durable and cost-effective solution for managing red mud waste [38]. Reduced resistance in other types of composites may be due to poor fiber-matrix adhesion. The bending resistance of long fiberglass E composite materials is higher than that of short woven fiberglass E composite materials. The least tensile strength is in short fibers. This could be due to a lack of matrix material in relation to the density fraction of fibers, resulting in lower tensile strength in long glass fiber composites [39]. Figure 1 shows the tensile test results of fiber-/filler-reinforced polymer composites.Glass–fiber-reinforced nanocomposites could significantly improve mechanical properties, thanks to the drying schedule, and were silanized using a high concentration of silanes in the solvent. In nanocomposites, the tensile module and tensile strength were increased by 30% and 37%, respectively [40]. Transmission electron microscopy was used to examine nanocomposite morphology, with results showing fractured surfaces [39]. Hemp fiber bundles were alkalized at concentrations ranging from 0.8% to 8% NaOH, and the change in surface morphology was studied using scanning electron microscopy. The study reveals that 4% and 6% of NaOH treatments resulted in the highest Young’s modulus and tensile strength of 65 GPa and 1,064 MPa, respectively, when the fibers were tested in tension. Untreated fibers had a Young’s module of 38 GPa and tensile strength of 591 MPa, respectively. The most solid-treated fibers were used to strengthen the liquid matrix of the cashew shell [41]. Table 1 compares the tensile properties of fiber-/filler-incorporated polymer composites.Table 1
Tensile properties of filler-/fiber-reinforced composites.
S. no.MatrixFiber/filler typeObservationsReference1PolyesterEggshell powder/nanoclay1.5 wt% nanoclay-reinforced composite showed 29.28 MPa tensile strength which is superior to other compositesGanesan et al. [19]2PolyesterSisal fiber/redmudThe tensile strength of the 3-ply composite with red mud is lower than the tensile strength of the 3-ply composite without red mudShanmugam et al. [42]3EpoxyNanoalumina particlesHigher concentrations of nanoalumina particles and coupling agents resulted in lower tensile strength due to decreased reticulation density of the polymerDhanapal et al. [43]4EpoxySisal fiberThe chemical treatment of sisal fiber significantly improved tensile strengthArpitha et al. [44]5Vinyl esterTamarinian fiber15 wt% reinforced composites have a tensile strength of about 34.1 MPaStalin et al. [45]


## 4. Flexural Performance of Fiber-/Filler-Based Polymer Composites

The bending strength compared to the applied load was determined using the bending properties. These properties of composite materials were crucial in determining the resistance before the breaking load. By increasing the volume of fibers from 30% to 50%, the bamboo-reinforced polypropylene composite improved its bending resistance [46]. Fiberglass-reinforced biomass waste such as spruce, maple, and substitute grass that was heated to 700°C for 60 min to produce biochar. The biochar weight percentage on 5% and 10% addition of glass fiber-reinforced polymer composition has a higher flexural performance (850–950 MPa) than the biochar weight percentage on 5% and 10% biochar biocomposite (700–830 MPa) [47].The different weight percentages of calcium carbonate with a long fiberglass-reinforced polyester matrix were studied for fiber orientation, fiber length distribution, and mechanical properties. According to the results, the addition of calcium carbonate to long glass fibers reduced flexural resistance [48]. The melt mixing technique is used to fill a single-walled carbon nanotube with polyester matrix with various weight percentages of single-walled carbon nanotube filler, including 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, and 2.0. In the presence of nanotubes, the mechanical bending properties showed a significant increase in stress, up to 0.75. Bending tests show that the incorporation of ≥1% of nanotubes reduces bending resistance due to low interfacial adhesion compared to the nonreinforced polymer [30].The injection molding method is used to investigate the mechanical properties of the red mud-reinforced polyester matrix (0, 5, 10, 15, 20, 30, and 50 wt%). Red mud-reinforced PP matrix. Bending resistance filled with red mud, depending on the study, and bending resistance, modulus increased [49]. Wood–plastic composites are a category of materials which have been developed to reduce dependence on mineral oil-based plastics. The effect of the addition of hard wood specific to composites on their flexural properties was studied [50].A parametric study of biochar/wood/polypropylene composites was carried out in order to assess the significant material factors that could affect the mechanical properties of the resulting composites. The presence/absence of coupling agent and wood, the particle size of the biotank, and the melting flux index of polypropylene are the four factors studied using the Taguchi experimental technique. For example, the percentage of optimal weight of the filler in the bending force [51]. Composite samples of polypropylene reinforced with sugar cane soda fibers were cut and subjected to mechanical tests to determine flexural strength. The bending properties show that the composites did not have good adhesion between the fiber and the matrix; however, the insertion of the fiber improved the bending module and the rigidity of the material [52]. Adding bamboo carbon particles, the size of a micron enhances the bending force and toughness of the automatic solidification cement composite [53].The flexural behavior experimental study on polypropylene filled with date palm seed biochar results showed a significant improvement in the flexural properties, indicating a good improvement in the adhesion between the filler and the matrix. Add 2–4 additional weights. The 10μm heat-treated biochar particle prepared from composite increased tensile strength and deformation at fracture [54]. Biochar made from empty palm oil fruit bunches at a pyrolysis temperature of 700°C in the presence of nitrogen is reinforced in the polypropylene matrix. The effect of adding 10%–40% biochar to empty fruit clusters increased the bending force by 20% [55].The compression, split tensile, and flexural strength tests on PET bottle fiber-reinforced concrete cube and cylinder reported that an improvement in properties with 2% fine aggregate was noted when replaced by PET bottle fiber and a decrease in properties when the PET bottle fiber content [56]. PET bottles filled with brick furnace dust, bagasse ash, and fly ash are more resistant to compression than conventional bricks. Compared to conventional bricks and brick masonry, the declared cost of brick was 41% lower and the cost of masonry for PET cylinders was 22% lower. The steel mesh was sandwiched among the PET cylinders [57].Production of plastic earth bricks by varying the plastic waste content, laterite stone, and bitumen to 2% by weight of laterite stone. It was made by mixing the laterite stone in melted plastic, then cooling it in a mold of the required size, cooled with air or water. The laterite and laterite combination contained 65%–70% plastic and 2% bitumen by weight and had a compressive strength of 8.19 N/mm2 (higher than laterite stone: 3.18 N/mm2) and a water absorption of 0.9536% (lower than laterite stone: 14.58) [58]. The wood flour biochar composites filled with polypropylene provide increased flexural strength when the biochar weight percentage was increased to 25% because of particle agglomeration, increasing the percentage of charcoal results in a decrease in flexural strength [59]. PP composites full of talc powder and rice bark show the greatest bending force [60]. PP composites reinforced with corn charcoal and ash wood manufactured with different percentages of charcoal reinforced with the die revealed the 10% weight. The highest value was noted in completed composites [61].With regard to the effect on the bending strength of glass/epoxy laminated composite materials, the experiments were carried out under two different conditions. According to the results of the four-point bending test, the bending strength of the specimens decreased by ∼25% and 42% [62]. In this article, the four-point bending and buckling tests can be repeated for different materials, such as hybrid composites, nanocomposites, or nanoparticle added, to determine the loss of flexural and buckling performances. To improve bending performance, the best construction orientation for parts manufactured using laminate material manufacturing technique. There are four different types of specimens made in the study, each with a different construction orientation. Four loading point machines were tested to determine the mode of failure and the vessel’s best orientation for the bending load was determined. For the maximum load, it was found that a 45° orientation of the vessel was the best prior to failure and had the highest bending strength [63]. Figure 2 shows the flexural test results of some fiber-/filler-reinforced polymer composites.Figure 2
Flexural test results of fiber-/filler-reinforced polymer composites.Comparison of the bending characteristics of various fiber-reinforced channel posts with a brand-new fiber-reinforced channel postmaterial for dental applications. Several (17) FRC poles are kept at room temperature and immersed in water for 2 weeks before being tested. The bending resistance was measured using the three-point bending test. Based on the results, the control material had the highest bending resistance. According to the composite, the bending module of the test specimens was reduced by 10% [55]. Table 2 compares the flexural properties of fiber-/filler-incorporated polymer composites.Table 2
Flexural properties of filler-/fiber-reinforced composites.
S. noMatrixFiber/filler typeObservationsReference1PolypropyleneBamboo fiber30–50 wt%, bamboo-reinforced polypropylene composite have improved bending resistanceBehera et al. [64]2VinylesterGlass fiber/biocharHigher flexural performance (985 MPa)Wallace et al. [65]3PolypropyleneGlass fiber/calcium carbonateAddition of CaCO3 in long glass fiber reinforced polypropylene composites increased the stiffnessAimonen et al. [66]4EpoxySisal/glass fiber/Silicon carbideIncorporation of silicon carbide filler can reduce the voids and enhance the flexural propertiesArpitha et al. [67]


## 5. Impact Performance of Fiber-/Filler-Based Polymer Composites

The composite polymers were subjected to a shock test to determine their ability to resist a sudden load. In this test, a reliable application of composite materials may be recommended. The impact of various natural fiber combinations on baggase ash-filled epoxy composites, including sisal/kenaf, sisal/flax, banana/kenaf, and banana-/flax-reinforced epoxy composites using a vacuum bag-assisted resin transfer method, fly ash particles were reinforced to the extent of 1%, 3%, and 5% in various combinations of fiber and epoxy composite. According to the results, only the resistance to impact has been significantly improved with the addition of up to 3% ash content. The 1% epoxy ash-filled sisal/flax and sisal/kenaf composites exhibited higher crashworthiness [68].To prepare the multiwalled carbon nanotube filler and jute fiber-reinforced epoxy composites, different weight percentages were reinforced, ranging from 2% to 8%. The impact resistance would have been greatly improved by adding carbon nanotubes over a pure tube. Due to the bond between the nanocarbon filler and the composite, ∼6% of the composites reached their maximum crashworthiness [69]. The impact strength of vinyl ester matrix composites filled with 50% peanut shell was increased to 42.91 kJ/m2. In addition, the load’s crashworthiness was reduced. Due to the excessive filling dose, the impact force is reduced due to the bad interfacial connection between the filling and the bed [70].Experiments on sisal/glass fiber laminates with silicon carbide-reinforced epoxy composite laminates were prepared using a manual method in combination with vacuum bagging. Glass fiber-reinforced epoxy composites have a higher impact resistance of 1,470.5 J/m compared to all laminate composites. The fiberglass and matrix exhibited good bonding behavior and could absorb most of the impact energy [67]. The impact strength of hybridization of rice husk, walnut shells, and coconut shell powders reinforced with glass fiber/bioepoxy composites was made to powders and were divided into three groups, with each group selecting an equal weight percentage in both dry and wet conditions. The combined walnut and coconut shell hybrid absorbed 20.9 J under dry conditions and 21.3 J under wet conditions, based on maximum impact resistance [71].Studies comparing epoxy and polyester fiberglass-reinforced composites with loads such as rice bark, wheat bark, and coconut are used in both matrices [72]. Impact tests on prepared composites found that polyester composites are more resistant to impact than epoxy composites. Notably, the addition of coconut particles contributes significantly to the impact strength of both matrices [73]. The significant increase in impact resistance in different lengths of coconut fiber and reinforced coconut shell particles in polyethylene composites with fiber length has increased to 30 mm. However, the 30 mm length of filled composite envelope particles produced the highest impact resistance module, which was 0.061 GPa. Increased fiber length reduced impact resistance, expressed in terms of deboning, fiber cracking, and fiber removal [74].The hybrid oil palm mesocarp fiber and nanoclay-filled polylactic acid/polycaprolactone composites with 10% composite fibers provided an impact strength of 48.43% higher. The improvement in impact resistance is due to the hydrophobic behavior of the polymer matrix, which was reinforced by silane treatment [75]. The impact strength of chemically treated jute fiber-reinforced eggshell powder and nanoclay filled polyester composites is compared to untreated jute fiber, sodium hydroxide-treated jute fiber, and each equal combination of filler reached the maximum impact strength in this experiment. Because the filler is mixed evenly, there is good adhesion between the fiber and the matrix, which reduces crack propagation. Untreated jute fiber composites had low impact resistance, and the filler formed a build-up that decreased impact resistance [19].Maleic anhydride polypropylene and maleic anhydride polyethylene treated rice husk filler-reinforced polylactic acid composites on hot compression molding have been used to incorporate the coupling agent into composites containing 2, 4, and 6 wt%. The impact resistance of treated maleic anhydride polypropylene was reduced by up to 4%, depending on the impact results. Other than this, the coupling agent did not affect the impact strength of the composites. Meanwhile, the low interfacial bond between the fiber and the filler material caused by this filler material tends to increase the impact failure. However, due to improved particle dispersion, the 6% composite is expected the highest impact force [76]. Various fillers such as fly ash, aluminum oxide, magnesium hydroxide, and hematite powder-reinforced E-glass/epoxy composites were used at various concentrations (10% and 15%), indicating that the fly ash 10% filled glass/epoxy composite revealed the highest impact strength when compared to others. To withstand the crack initiator, the fly ash filler acts as a better binding agent between the fiber and the die. Adding 15% fly ash composites reduce the resistance to impact, as more voids are produced, reducing the resistance to impact [77].Wood fibers and hydrophobic polypropylene composites improve impact resistance through interfacial adhesion between fiber and filler material. Maleic anhydride-modified polypropylene was utilized. However, in this study, the coupling agent did not influence the composite impact force. Following the impact strength studies, the addition of loads was found to reduce the impact strength. Low impact resistance was observed due to the thermal degradation of the fiber during compounding [78]. Impact force measurement using composites made of polycarbonate, acrylonitrile, butadiene, and styrene with talc powder as a filler and fiberglass as a ready-made reinforcing agent. The impact strength results of the talc/glass fiber filled polycarbonate/acrylonitrile-butadiene-styrene composites are shown in Figure 2. However, increased glass fiber content reduces impact resistance, whereas composites containing 7.5% talc and 5% fiberglass had the highest impact resistance [79].The treatment of the silane coupling agent with bamboo fibers reinforced with polypropylene composites gives rise to observations in the form of composite plates with percentages of different weights of 10%, 30%, and 50%. The results show that compared to untreated fibers, treated fibers reduce impact properties by up to 30%. The lower impact strength is due to the silane coupling agent reaction resulting from the condensation reaction in the cross-link chain. The percentage of charge handled by bamboo fiber, on the other hand, is the highest percentage of composites, indicating the highest impact force [80]. Impact studies on three types of filling materials were reinforced with glass fiber-/epoxy-reinforced composite materials with a weight percentage of 3%, zinc oxide, nanoclay, and flying ash. The greatest impact was observed in glass fiber/epoxy composites filled with fly ash/nanoclay that improved by 18% [81]. The impact strength test results for various fiber-/filler-reinforced polymer composites are shown in Figure 3.Figure 3
Impact strength results of some fiber-/filler-reinforced polymer composites.Studies comparing bone powder and shell powder reinforced with coconut fiber/polyester composites resulting in coir bone powder/polyester composites having the highest strength. The SEM image shows that no fibers are extracted from the bone powder composites, which causes the fiber to expand and rupture [82]. Different sizes of wood flour particles were reinforced with polypropylene composites to enhance adhesion, a bonding agent made of polypropylene-grafted maleic anhydride was used. However, compared to pure wood, wood flour composites are less resistant to impact [83]. This may be explained by the fact that wood meal particles generate stress concentration points that cause crack propagation. The addition of charge particles increased the build-up of composites, which reduced the impact force. The small particle size of the wood flour composites had the greatest impact strength relative to the large particle size [84].The manual deposition method for filling peanut and luffa fibers with epoxy composites, the fiber underwent an alkaline treatment before being analyzed for its mechanical properties. At 1.6 J, 30% of the maximum impact force was occurred. In addition, the addition of fillers reduces impact resistance, while alkaline fibers improve impact resistance [85]. Reinforced polymers of iron powder such as polystyrene, polypropylene, and high-density polyethylene for comparison with all composite combinations, the impact force of pure high-density polyethylene revealed the highest strength. Whereas adding iron powder to composites has a negative effect, lowering the impact force [86].In glass fiber silicon carbide-reinforced epoxy composites, silicon carbide fillings of 5%, 10%, 15%, and 20% are used. The impact strength was measured, and the 15% increase in load was found to significantly increase the strength. Although more energy is absorbed, a better connection between the fiber and the infill material resists cracking. Because of the low adhesion, the impact force was reduced by 20% when the filling percentages were added [87]. A comparative study on carbonized and uncorbonized particles as reinforcement on polyethylene composites in various percentages ranging from 10% to 50% reported that the addition of carbonized baggase composite materials resulted in up to a 30% improvement in properties. Furthermore, when the number of particles exceeds a certain percentage, the properties suffer as a result of poor bonding between the filer and the matrix [88]. Pyrolysis process at 450°C with different chars made from wood shelving char, pine cone char, and plastic waste char to measure the mechanical properties. These types of filled composites were compared to those of neat epoxy, and it was found that the reinforcement of plastic waste char filler composites provided better impact strength [89]. The mechanical properties of fiber- and filler-reinforced polymer composites are shown in Table 3.Table 3
Mechanical properties of polymer composites.
S. no.MatrixReinforcementTensile strength (MPa)Flexural strength (MPa)Impact strength (kJ/m2)Reference1EpoxyBiocarbon38032372.7[90]2Polylactic acidActivated biochar16.2853.813.67[91]3High-density polyethylenePoplar biocharNil4523[92]4High-density polyethyleneRice husk biochar29.0534.95Nil[93]5High-density polyethylene and polylactic acidSwitchgrass biochar558023[94]6PolypropyleneLandfill wood35.867.2Nil[95]7PolypropyleneBiochar and chopped miscanthus fiber3455140[96]8VinylesterSansevieria cylindrical fiber and corncob72.71347.6322.51[97]9Nylon 6/polypropyleneBiocarbon6611075[98]10PolyesterOil palm empty fruit bunch biochar423204[99]


## 6. Solid Particle Erosion Wear of Fiber-/Filler-Based Polymer Composites

Erosive wear on solid particles is a material removal process that can lead to composite failure. The hard particles of eroded food have an impact on the target sample which causes the loss of material. The erosion properties of CaCO3-/glass-reinforced polyester composites at different particle sizes (1, 2, 3, 5) filler have been reinforced with a polyester matrix (40%, 50%, and 60%). The maximum erosion rate was estimated at the 90° impact angle because the hard particles were brittle materials, which caused the maximum cracks [100]. The erosion feature of epoxy composites filled with silica and zinc oxide with different weight percentages of epoxy composites was investigated. Erosion studies were conducted with variable angle, velocity, and grain size parameters. The rate of erosion increased with increasing angle, flow, and speed. Compared to zinc oxide, reinforced silica epoxy composite exhibited a minimal erosion rate [101].The 6% of TiO2-filled polymer composites had the lowest rate of erosion, according to erosive wear experiments using TiO2 and ZrO2-filled bamboo and glass fiber reinforced epoxy composites with varied percentages (3%, 6%, and 9%). The addition of fillers results in poor bonding between the matrix, which has increased the rate of erosion [102]. Hybrid filler (WC Ta/NbC)- and fiberglass-reinforced epoxy composites prepared by resin transfer molding. Erosion studies lead to variable angles (30, 60, and 90) over two temperature conditions, in particular ambient and high at 90°. The environmental temperature angle was found to be 30°. When the temperature was high, the rate of erosive wear also increased, but the increase in angle also increased the rate of erosion [103].Erosion behaviour of red mud-filled polyester–pineapple composites made with varying ratios, such as 10% and 20%. The erosion parameters of angle of impact (30°, 60°, and 90°), velocity (72, 100, and 129 m/s), and discharge (1.0, 2.5, and 3.3) properties were analyzed. The minimum erosion rate was determined for 10% of the red mud-filled pine angle 60°, the erosion rate 72 m/s, and the eroded flow rate 2.5 g/m2 [104]. Erosive wear properties of epoxy composites filled with jute fiber and SiC particles were reinforced in different percentages, namely, 20%, 30%, and 40% for jute fiber and 10% and 20% for SiC, respectively. During erosion at a 60° angle of impact, the maximum erosion rate was observed using 40% jute-reinforced epoxy composite. Increased strengthening of the infill particles resulted in poor adhesion, which increased the rate of erosion [105].Through the screw molding process, volcanic ash-reinforced polyphenylene sulfide composites were prepared and the erosive wear rate studies confirm that there is a significantly increased when the percentage of volcanic filler in the composites is increased. At an impact angle of 90°, erosion wear is identified at different angles and the maximum erosion rate is identified [106]. The optimum erosion rate of boric acid particle-reinforced epoxy glass fiber composites was studied by a number of factors in the Taguchi design, including impingement angles, fiber direction, and velocity. For all composite combinations, the maximum erosion rate is observed at an impact angle of 30° [107]. Erosion activity of bamboo epoxy composites filled with red mud and glass epoxy was reported as hybrid composites. The Taguchi experiment, which was used to detect the minimal erosion rate, found that bamboo composites filled with red mud exhibited the lowest erosion rate. Because of the semiductile behavior of composites, maximum erosive wear was calculated using the impact angle of 60° [108].By manual installation method, alumina-filled coir-fiber-reinforced epoxy composites are prepared. Both the coir fiber (3, 6, 9, 12, and 15 mm) and the alumina filler (5, 10, 15, and 20 wt%) were reinforced epoxy composites with various lengths (3, 6, 9, 12, and 15 mm). When the angle and speed factors were changed, the 12 mm filled bamboo epoxy composites had the lowest erosion rate compared to the fiberglass composite [109]. The erosion properties of geopolymer composites containing fly ash at different angles and speeds were determined using alumina particles. On an angle of impact of 30°, the highest rate of erosion was observed, and as the speed increased, so did the rate of erosion. For this angle to propagate the maximum erosive wear of composite materials, microcracks can be produced [110].The borosilicate glass filling material-reinforced the epoxy matrix by hand to detect the erosive wear rate, they were arranged in an orthogonal lattice. The angle of impact and the size of the infill material have the greatest impact on composite erosion rates [111]. Copper slag waste- and jute fiber-reinforced polyester composites have undergone chemical treatments such as sodium hydroxide and calcium hydroxide. Copper slag represented 10% and jute fiber represented 40% of the polyester resin used in compression molding. Erosion testing was conducted on prepared samples, and calcium hydroxide composites exceeded sodium hydroxide composites in terms of wear resistance. To reduce erosion resistance, copper slag particles were formed as a good interfacial bond between the fiber and matrix [112]. Erosion wear properties of short glass fiber polyester composites-reinforced with aluminum oxide filler were found to have increased velocity penetration and progress to more material loss, while increased impact velocity is one of the influence factors that the erosion wears rate velocity increase also increases the erosion rate. The maximum erosion peak was found at an angle of 75°, indicating that current composites exhibit semiductile behavior [113].Comparison erosion studies on glass bamboo hybrid epoxy composites with the fillers titanium oxide and zirconia oxide have been used in weight percentages of 3%, 6%, and 9% filled glass bamboo epoxy composites. The 6% zirconium oxide-filled glass bamboo epoxy composite was the least erosive due to the capacity of the filler material to improve the adhesion of the fiber to the matrix [102]. The erosive wear experimental results of ultrahigh molecular weight polyethylene and aramid fiber reinforced epoxy composites were conducted at different impingement angles, three different velocities, and a constant standoff distance in this study. Compared to unfilled aramid composites, the erosion rate indicates that ultra-high molecular weight polyethylene- and aramid-reinforced epoxy composites have the lowest erosion rate. The improvement of erosive wear is dependent on the filler concentration, so the maximum erosive wear rate was observed at a 60° impingement angle, indicating that the material is semiductile [114].Erosive wear analysis of tungsten carbide powders filled with glass–fiber-reinforced epoxy composites at various impact angles and impact velocity erosion ratios was conducted. For epoxy glass composites filled with tungsten powder, the maximum wear rate was observed at 90° impact angles, demonstrating the fragile nature of the material. The SEM images on erosion wear performed polymer composites are shown in Figure4. The SEM images revealed more serious damage to the unfilled glass epoxy composite, indicating that the tungsten powder in the composite slowed the rate of erosive wear [115]. Experimental results on polyvinyl pyrrolidone composites reinforced by short-date palm leaf fibers on the erosion endpoint were tested at different speeds, and the impact velocity endpoint was determined. The results showed that the unfilled matrix reached its peak erosion rate at a 30° impingement angle, while the fiber-filled composites reached their peak erosion rate at a 45° impingement angle. The impact velocity shows that as the velocity increases, composites lose more matter [116].Figure 4
Erosive wear SEM images on glass fiber-/tungsten powder-filled epoxy composites.Erosion studies on wood apple shell particles- and carbon block-reinforced epoxy composites prepared by the pyrolysis process with varied epoxy composites of 5%, 10%, 15%, and 20% were tested at various impact angles, and it was found that adding 20% carbon block composites to the combination resulted in the lowest erosion rate. Compared to apple shell particles, the carbon block material presents a better reduction in wear due to better matrix adhesion [117]. Erosion wear rate of boiled and unboiled eggshells reinforced with epoxy composite was reported, which was fabricated through the hand layup method with various filler weight percentages of 4%, 8%, and 12%. The erosion test was conducted with varying angles of impact, speed, and environmental conditions. According to the results, 4% uncooled eggshell epoxy composites had the lowest erosion rate. Because the boiled eggshell contains some moisture, the vacuum production of the epoxy composite is a reason to achieve maximum wear on epoxy composites. Furthermore, a peak erosion of the composites was discovered in 12% of the composites due to the shape of the particle agglomeration [118].The optimal erosion rate of composites reinforced with iron mud residue and glass fibers was observed using an artificial neural network. Compared to other composites, the 20% red sludge-filled composite showed the lowest erosion rate. Fiber fractures, microcutting, voids and plastic deformation of composites are all studied in morphological studies [119]. The Taguchi analysis tool was used to determine the best erosion rate for red brick dust to incorporate epoxy composites using a manual layering method. Impact speed is the most important factor among all factors, depending on the variation of the parameters used in the erosion wear analysis. Studies by SEM concluded that red brick dust was evenly distributed in epoxy composites [120]. The Taguchi statistical tool was used to determine the best erosion factors in alumina- and fiberglass-filled polyester composites. Pure glass polyester composites had the highest rate of erosion due to matrix deboning. Despite the fact that it has been consistently demonstrated adding infill alumina may slow erosion significantly. Morphological studies revealed crater formation, multiple fracture, and fiber and fill stack exposure [121].The impact velocity, the angle of impact, the percentage of silicon carbide, and the eroded size were all studied on glass fibers and SiC-reinforced polyester matrix composites. The Taguchi method is used to determine the erosion efficiency of the optimal parameter and the minimal erosion rate. Compared with other factors, the impact velocity effect is lower, and the maximum erosion rate observed at a 70° angle proves the semiductile method [122]. Carbon fabric-filled polyetherimide composites using the impregnation technique replaced the carbon fabric, which contributes 40% of the matrix, were used to perform erosion tests at various angles of impact. The maximum erosion rate was observed at an impact angle of 30°, which indicates the material is ductile. Also, the rapid hard particles impacted each other, the more material is lost via factors such as deboning, microcutting, and fracture [123]. The erosion-induced wear rate of granite particles filled with glass/epoxy composites was studied. The erosion test consisted of three different parameters: the size of the erosion, the speed of impact, and the angle of impact. Adding a granite charge to glass epoxy composites enhances the erosion resistance of composites. The Taguchi analysis showed minimal erosion. Crack propagation, ploughing, transverse cracking, and cratering mechanisms were studied using SEM [124].Comparison of erosion studies on alumina and silica particles used as eroded foods with fiberglass-reinforced polyphenylene sulfide composites. Various angles of impact were used in this study, such as 15°, 30°, 45°, 60°, 75°, and 90°, respectively. The maximum erosion rate was determined by using silica sand at a 45° impaction angle and alumina particles at a 30° impaction angle. Compared with alumina, silica sand particles have the lowest erosion rate. They concluded that erosion-induced wear begins on the bed and continues through fiberglass failure and uncoupling [125]. The vacuum-assisted resin transfer casting technique is used to understand the effect of different percentages of marble powder on needle-perforated, nonwoven jute felt epoxy composites. Changes in the speed, angle of impact and size of erosion were used in the erosion test. The ANOVA tests were conducted to determine the factors that affect the erosive wear rate. This study found that the increased reinforcement of marble powder in composites greatly reduces erosive wear resistance [126].The effects of erosion on glass fiber-reinforced epoxy composites filled with fly ash were studied according to various parameters such as eroded face, angle of impact, and velocity. The fly ash infill was charged to a maximum of 4 g, indicating the lowest erosion rate. The results showed that compared with unfilled glass epoxy composites, this charge of fly ash reduces the rate of erosion. On fiberglass composites, the maximum erosion rate was observed, while the weak bonding of the fiber matrix was observed [127]. The erosion results of the impact angle, eroded discharge, and impact velocity were determined using Taguchi analysis on sisal fiber-reinforced polyester matrix composites filled with red mud. Compared with unfilled composites, this study found that adding a red mud filler increased erosion resistance [128–138]. The rate of erosion wear increased substantially as the impact speed increased. The presence of the crater, the fracture of the fibers, the microcutting, the ploughing, and the plastic deformation were studied with the aid of morphological studies [139–143].


## 7. Summary

The tensile, flexural, impact, and erosion characteristics of polymer composites made by including various types of fiber and nanofiller are presented. The mechanical characteristics of composites including both fiber and filler were demonstrated to increase their strength. This phase of reinforcement may be responsible for the enhanced binding properties, and its ultimate function is to transmit mechanical loads. The erosion characteristics of several fiber and filler loading composites are addressed, and the findings reveal that the erosion peak is mostly detected at an angle of 60°, confirming that the material is semiductile.


## 8. Conclusion

The composites produced by combining fibers with nanofillers have excellent mechanical properties, providing for a variety of structural applications. The inclusion of nanofillers increases the tensile strengths of pineapple, jute, hemp, sisal, jute, and glass fiber reinforced polymer composites. The results for flexural strength indicate a 30%–50% improvement in strength with enhanced load resisting capabilities. Earlier researchers demonstrated conclusively that the inclusion of nanofillers and fibers as reinforcement significantly enhanced the ability to absorb energy. Among all mechanical parameters, the percentage weight increase for impact resistance was between 60% and 80%. The composites’ failure mechanism includes insufficient dispersion of nanofiller particles, insufficient bonding, agglomeration, fiber pull out, etc.



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