Effect of abrasive grit grade on the abrasion wear behaviour of long banana-jute fibers reinforced hybrid epoxy composites

The effect of abrasive grit geometry on two-body abrasion wear behavior of long banana and jute fiber reinforced epoxy composites has been investigated. Epoxy (EP), Epoxy/4 wt% Banana fiber (BF)/4 wt%Jute fiber (JF) (EP8), Epoxy/8 wt%BF/8 wt%JF (EP16), Epoxy/12 wt%BF/12 wt% JF (EP24), and Epoxy/16 wt% BF/16 wt%JF (EP32) were the composite materials systems used for the investigation. These composites were processed and fabricated using hand—lay-up technique. The two body abrasion wear test was carried out in accordance with ASTM G99 under the influence of different SiC grit particles (180, 320, 400, and 600 SiC grit). The test was conducted at a room temperature under the abrasion load of 10 N and abrasion speed of 1 m s−1 over a distance of 100 m. The findings of the experiments revealed that wear response of composites depends on pressure, geometry of abrasion particles and their composition. The wear volume loss and specific wear rate decreases with increase in the rank of grit grade. Further, 16 wt% of fibers in composites exhibits the superior abrasion wear resistance. But the higher volume fraction of natural fibers in composites impaired the abrasion wear resistance. Higher rank of grit number was associated with the lesser wear volume loss because of the change in wear mechanism from abrasion to adhesion. In comparison to epoxy based composites, EP16 composite shows superior wear resistance. SEM images were used to examine the worn surfaces.


Introduction
The design and development of polymers and their composites have played a very significant role in automotive and structural applications.The self -lubrication, high strength to weight ratio, light weight, aesthetic appearance were some of the characters attracted the research bench.But the abrasion resistance of these polymer composites was poor because of their inferior mechanical properties, density and hardness.Because of these properties, polymer composites have failed to resist the load during abrasion under the impact of different performance conditions.Abrasion wear is the main cause of failure for most of the service components in mechanical industries.There are two body wear (2BAW) and three body wear (3BAW).However, around 60% of failure of polymer components in industries is caused by the action of two body abrasion wear [1].Some of the mechanical components subjected to abrasion wear are clutches, friction plates, belt drives, bearings and other agricultural equipment and chute liners etc The effect of abrasion under the action of two bodies was so severe and it needs to be controlled.When the abrasive materials like Silicon carbide, quartz, sand and such related particles rub against the soft polymer, they experiences the severe material loss due to abrasion.The effect of interaction has played the major role in defining the abrasion tribology of these polymer composites.The same problems with material loss due to abrasion occur frequently in mechanical applications.Polymer modification can resist the abrasion.Therefore, the automotive industries are moving towards polymer composites [2].
Natural fibers including jute, banana, Ramie, Sisal, drumstick, and Basalt fibers have been proved to be the best reinforcement agents for withstanding mechanical and tribological load during performance.
Epoxy is a polymer resin which is generally used in the production of polymer composites because of its ability of ease of flow and positive interaction with the reinforcing phase [3].The potential of polymer composites using different fillers and fibers must be explored when they were rubbed against hard abrasive particles.This is the hard situation of polymer composites under abrasion.To resist the abrasion load during two body interaction, design and development of polymer composites must be considered for the investigation.There are three methods for the polymer modification.Polymer blending, copolymerization and reinforcing polymers with fibers and fillers.To resist the abrasion load when interacting with the abrasion particles, the polymers were reinforced with fibers which will effectively improve the strength and hence the abrasion wear resistance.Many researchers have contributed their work towards the development of fiber reinforced polymer composites using natural fibers.The influence of adding graphite filler on the two body abrasion wear of carbonepoxy composites was studied and reported [4].They used SiC grit particles of 150 and 320 grade for the abrasion effect.Three material systems were selected for the study: Neat epoxy, epoxy with 20 wt% carbon fabrics and epoxy+carbon+5 wt% graphite filler.The investigation showed that the wear rate was lowered with the addition of graphite fillers.The wear loss has been declined due to the addition of carbon fibers.Further, the reinforcement effect of carbon fabrics has retained its effect up to 20 wt%.It was observed from the study that impact of 150 Grit SiC paper was more sensitive to wear loss when compared to 320 Grit.
The effect of reinforcing glass fabric on two body abrasion wear behavior of SiC filled glass-epoxy composites was thoroughly investigated [5].They showed the tribology of glass carbon composites under the impact of 600 and 1000 SiC grit particles.Also, tests have been carried out for the interaction effect at various abrading distances (25, 50, 75, and 100 m) under the effect of 10 N load.Results revealed that the presence of SiC abrasive particles had controlled the wear loss.The 600 grit abrasive particles exhibit the greater penetrating impact than others.Additionally, they reported to the research group that improved wear resistance during abrasion was mostly due to the superior mechanical properties of composites.For the structural integrity of epoxy-based composites, hybrid composites made of jute and rubber textiles have been demonstrated [6].They studied the two body abrasion effect using SiC abrasive particles with a 60 grit size.It was observed from the study that the wear pattern was consistent with standard tribology whereas the interaction mechanism was completely different.It was found that jute fibers have effectively resisted the abrasion load compared to rubber.
The impact of Tungsten carbide filler (WC) on the two body abrasion wear behavior of glass-epoxy composites was reported [7].They showed that the addition of tungsten carbide has successfully impaired the wear loss of glass-epoxy composites.They examined the wear behavior under the impact of varying sliding distances using two different abrasive materials.They showed that wear volume loss increases with increase in abrading distance.Further, the wear loss was greatly impaired by the inclusion of tungsten carbide.The main factor affecting the abrasion process was the synergy between glass textiles and filler.Compared to neat epoxy, hybrid composites showed better wear resistance.The impact of Nano-OMMT filler on the abrasion wear behavior of carbon epoxy composite has been discussed and reported [8].They studied the effect of abrading distance, abrading pressure and also the composition of composites on the tribological response of carbon epoxy composites.They used 180 and 320 Grit grade SiC abrasive particles.The investigation demonstrated that the tribological response depends on the size, weight, and duration of particles interactions.Further, they stated that the abrasion wear resistance was decreased by the addition of Nano filler.Furthermore, they mentioned that wear rate increases with pressure and decreases with distance.Investigation on the two-body wear behavior of clay and clay along with short carbon fiber filled Polyamide66/Polypropylene (PA66/PP) nanocomposites was reported [9].The reinforcement of clay in the PA66/PP blend was found to be detrimental to the abrasive wear resistance.The clay plus short carbon fiber filled PA66/PP blend exhibited better abrasive wear performance than the clay filled PA66/PP nanocomposites.According to the experimental findings, the influence of hybrid fibers has deteriorated the wear of composite materials.Further, the tribological loss of these composites has been decreased with increase of grit number.
The two body abrasion wear behavior of Areca sheath fiber reinforced polyvinyl alcohol composites has been studied [10].Areca fiber was modified with benzyl chloride to increase the adhesive strength of resin matrix.These composites were developed using melt mix method followed by injection molding.The areca fibers were loaded up to 40 wt% insteps of 10 wt%.The effect of abrasion load on the same composites was investigated.The findings of the test showed that wear volume loss increases with increase in sliding distance whereas decreases with increase in fiber volume fraction.Wear resistance is best defined by the modification agent.The effect of graphene filler on the two body abrasion behavior of Glass-Epoxy composites has been the subject of research [11].They developed these composites using vacuum bag molding technology.They studied the effect of load (2 to 10 N) and abrading distance (25 to 75 m) on two body abrasion wear behavior of graphene filled epoxy composites.It was observed that wear volume loss decreases with increase in volume fraction of filler.The effect of adding nano clay in to basalt filled epoxy composites was investigated for two body abrasion wear behavior [12].To investigate the abrasive response of these composites, different loads were applied.It was found that abrasive grit size, content, and interaction with soft polymers affected the wear response.The abrasion wear resistance of composites was accurately determined by the wear mechanism.The wear behavior of PA6 and its composites under two body abrasive wear mode and their abrasive wear volume maps were studied by Mimaroglu et al [13].They selected 25 wt% glass beads, 20 wt% talc and 30 wt% wollastonite fillers as reinforcement phase.The tests has been conducted for a normal load of 4, 6, 8 and 10 N at a velocity of 1 m/s for different abrasion surface roughness.It was proved from the abrasive wear volume graph that the lowest wear volume rate has been obtained by glass bead filler.
But the research bench has thrown the light on the defined reinforcement percentage of fibers on two body abrasive wear behavior of polymer composites.The effect of higher loading of Ipomoea carnea's fiber on the two body abrasive wear behavior of epoxy composites has been reported [14].They showed that the incorporation of Ipomoea carnea into the epoxy significantly reduces the abrasive wear.They showed that reinforcement effect up to 20 wt%of fiber could significantly controlled the wear loss due to abrasion whereas poor performance has been exhibited at higher loading of fibers (40 wt%).At this stage, the reinforced fibers have removed particulates from the matrix resin due to poor interfacial adhesion.Abrasive wear was very sensitive to normal load relative to sliding speed and it increases slightly with increasing sliding speed.The average wear intensity increases with increase in sliding distance.The effects of sliding velocity and load on the two body abrasive wear behavior of chemically treated coir fiber filled epoxy composites was reported by Khan et al [15].They reported that the specific wear rate due to abrasion was decreased due to the addition of these fibers compared to neat epoxy.The effect of alumina filler on the two body abrasive wear behavior of glass fiber reinforced epoxy composites was reported [16].They showed that alumina filled composites exhibits the superior abrasion wear resistance compared to glass filled epoxy.The effect of SiO 2 filler on the two body abrasive wear behavior of glass fiber reinforced epoxy composites was reported [17].They showed that 10 wt% SiO 2 filler in composites exhibits the superior abrasion wear resistance compared to glass filled epoxy.The experimental results showed that wear volume loss decreases with increase in filler loading and increases with increase in abrading distance.The abrasive wear behavior of liquid crystalline polymer (LCP) fibers and glass fibers reinforced hybrid composites using a two-body abrasion tester under different applied loads has been investigated [18].They concluded that the incorporation of LCP fiber results in improved wear performance of glass fiber reinforced linear-low density-polyethylene (LLDPE) composites.The effect of addition of Molybdenum disulphide (MoS 2 ) on the two body abrasive wear behavior of epoxy with/without glass fiber mat reinforcement has been reported [19].They used 10 wt% of MoS 2 filler in composites.They noticed a significant reduction in specific wear rate and wear loss after the incorporation of MoS 2 filler that allowed less wear of matrix during abrasion which in turn facilitated lower fiber damage.The effect of bamboo powder on the two body abrasive wear behavior of epoxy composites has been reported [20].It was found that weight loss of polyester composite decreases with increase in sliding distance.The abrasion study on the effect of fiber content on abrasive wear performance of Lantana Camara fiber reinforced composites subjected to sliding velocity of 0.314 m s −1 and normal load of 5, 10, 15, 20 and 25 N has been reported [21].The optimum wear reduction was obtained in case of composites with 40 wt% fiber content.
The synthetic fibers like glass, carbon, aramid, Kevlar and others have proved their potentiality in defining the abrasion wear resistance of epoxy based composites and promised the automobile industries for the better materials.But higher volume fraction of these synthetic fibers leads to high brittleness and development of cracks across these composites.However, very less research were employing the natural fibers such as banana, jute, Ramie, and sisal fibers with epoxy as the base material in developing composites for abrasion wear resistance under two body wear mode.From the research bench, it was observed that potential of these natural short fibers was explored for sliding wear behavior.But the usage of these long fibers for resisting the abrasion load is not reported.But most of the components used in automotive applications experience the failure because of this abrasion load.But the development of composites using long fibers is very limited in supply.Further, the surface energy of these long natural fibers accounts for the enhancement of adhesive strength between matrix and fibers which will be the promoting factor for the development of abrasion wear resistance.Hence, critical study on the abrasion wear behavior of natural fibers filled composites is required.The principal factor in defining the abrasion wear behavior other than load, pressure, distance is the abrasive grit.Further, the tribological response during abrasion depends on the geometry of the abrasive particles used for the process.On the other hand, the hybrid effect of these natural fibers was not researched or published for the abrasion study.Therefore, the impact of abrasive particle geometry on two body abrasive wear behavior of these polymer composites needs to be critically investigated.The primary determinant of wear behavior is the impact of abrasive grit.In light of this, an effort was made to study the effect of particle size on the two body abrasive wear behavior of long banana and jute fiber reinforced epoxy composites under multipass conditions.

Materials, composites processing, and composites testing 2.1. Materials
The physical data of materials used for the production of composites is shown in table 1.The physical information provided by the supplier for the epoxy, hardener, long banana, and jute fibers are listed in table 1. Table 2 lists the designation and formulations of material systems in weight fraction percentage used in the processing of composites.According to rule of mixture of material formulation system, the weight fraction of the long natural fibers reinforcement for epoxy based composite should not exceed 30%.The effect of minimum weight fraction of each fiber (<5%) will avoid the overlapping of fibers.It may give the base for the future increase in weight fraction consideration in the epoxy based natural composites.

Processing of epoxy natural composites
The epoxy based natural composites were processed using hand lay-up technique.The composite plates were fabricated using dimensionally controlled mold box made of a wooden block of 100 mm×100 mm × 6 mm.The material formulations systems with fiber wt% of 8, 16, 24 and 32 having equal volume of long banana and jute fibers were used for the development of these composite plates.The Epoxy LY556 with hardener HY951 was used as the base matrix to process epoxy-based composites.To remove any residues of air bubbles that might have been present due to variations in the volume fraction of fibers, the designed proportion of resin-hardener of 10:1 was chosen and filled in the glass jar under the effect of a vacuum chamber.The mold plate can be released using a releasing agent applied over the release plate.A release agent spray has been applied to the inner surface of the mould in order to make it easier for the plate to release.The composite mixture was put in the form of a smooth layer with a thickness of 2 mm once the mould was positioned over the glass plate.On the top of the composite layer, the fibers with designed volume proportion were also applied.The compaction pressure was applied to for a period of around 72 h.In order to prepare specimens for various tests, the laminated composites produced by the aforementioned procedure were cut in accordance with ASTM requirements.The production lay out along with the processing mold with specimens for testing is shown in the figure 1.

Testing of composites
The two body abrasion wear behavior of natural fibrous composites was studied using pin-on-disc machine (Ducom, Bangalore) in accordance with ASTM G99 (figure 2).The prepared sheets were cut into specimens of uniform size of dimensions 8 mm × 8 mm × 3.2 mm.To ensure a uniform and homogeneous contact surface during interaction with the disc surface, these specimens were rubbed against 600 Grit SiC abrasive paper.These samples were glued to a steel pin of dimension 27 mm length and 8 mm diameter using proper adhesive.An electronic weighing balance with 0.0001 gram accuracy was used to measure the initial and final weight of the test specimen.The test was conducted using SiC abrasive papers with 180, 320, 400, and 600 SiC Grit grade.The SiC abrasive paper is pasted on to the steel disc and a test run is conducted.After the test, the worn specimen weight is determined using the electronic balance.Three samples were used for the test and the average data was considered for the data representation.The loss in weight gives the wear loss (W) and is converted into wear volume (ΔV) with the help of experimental density (ρ).The wear loss (ΔV) and specific wear rate (Ks) are determined using equations (1) and (2) respectively.Separate grit paper was used for each and every test trail.
The experimental density was determined as per ASTM D2270 method for all the designated composite systems under investigation.The density details of the investigated composites are shown in the table 3. ´- Where ρ = density (g/cm 3 ), F, load (N) and D, abrading distance (m)

Results and discussion
3.1.Impact of grit geometry on the tribological response in two body abrasion wear of epoxy fibrous composites The abrasion wear behavior of epoxy fibrous natural composites was examined using ASTM G99 method in a two-body abrasion wear mode.The second body effect has been introduced through the silicon carbide abrasive papers as a test parameter were 180 Grit with an average particles size of 71 μm, 320 Grit (particle size 46.2 μm), 400 Grit (particle size 32.5 μm) and 600 Grit (particle size 26.5 μm) [9].The abrasion test has been conducted for a total abrading distance of 100 m under a 10 N abrading pressure through a velocity of 1 m s −1 at room temperature.The average size of the abrasive particles was varied with respect to grit number.Therefore, effect of abrasive SiC grit paper has played significant role in defining the abrasive wear behavior of the aforementioned composites.The mechanical properties such as tensile strength, ductility, hardness and fracture energy are some of the factors which promote the abrasion resistance.The Ratner-Lancaster factor which is the product of rupture stress and rupture strain (σε) has been the crucial factor in determining the two body abrasion wear resistance [8].Table 3 lists some of the potential mechanical properties that helped epoxy-based natural composites to withstand the abrasion wear.The results of the investigation showed that the wear volume loss of the fibrous composites is function of geometry of the abrasive grits, composition, and test conditions.The volumetric loss of fiber-reinforced epoxy-based natural composites decreases as the rank of abrasive grit number increases [7].
Figures 3(a) and (b) shows the two body abrasive wear response of epoxy-based jute-banana natural composites which is evaluated through volumetric loss and specific wear rate.The effect of different geometry of abrasive particles was investigated.Figure 3(a) showed the effect of abrasive grit grade on the wear volume loss of epoxy fibrous natural composites.It was observed from the analysis that the hard penetrating abrasive action of silicon carbide particles was extremely sensitive to polymer composites.Therefore, the effect of abrasive particles  exhibited by the different grit number of silicon carbide particles had a considerable impact on the wear loss of natural composites.The wear volume loss of neat epoxy (EP) under the abrasive action of 180 Grit was 57 mm 3 under the test conditions.The wear volume loss decreases with increase in rank of grit number [22,23].Similar observations were noticed when the epoxy had the abrasion action under the influence of 320 and 400 grit number.Proportionate wear loss has been exhibited by EP composites under the action of aforesaid SiC Grit.But the wear volume loss under the effect of 600 grit SiC particles was les compared to all the tested composites.
The wear volume loss of 30 mm 3 has been exhibited by Neat epoxy under the influence of 600 grit which is 47.36% less compared to the wear response at 180 Grit at the same experimental conditions.But the wear volume decrease with increase in the rank of grit number.Similar observations were drawn when studying the wear response of composites filled with natural fibers.Long jute and banana fibre filled composites had witnessed the wear volume loss in the similar trend as that of the rank of abrasive grit.However, the wear volume loss of epoxy fibrous composites was less compared to neat epoxy under all the abrasion conditions tested.The wear volume loss of 35 to 16 mm 3 , 32 to 13 mm 3 , 48 to 26 mm 3 , and 40 to 19 mm 3 was exhibited under the action of 180 and 600 grits respectively by EP8, EP16, EP24, and EP32 composites.According to the results of the investigation, EP8, EP16, EP24, and EP32 composites showed a 56%, 44%, 16%, and 30% decline in wear volume loss against neat epoxy when exposed to 180 grit abrasive particles.The effect of 180 grit abrasive particles results in high wear volume loss due to coarse and large sized abrasive particles whereas the 600 Grit abrasive particles caused the less wear volume loss due to fine and small sized abrasive particles [5,13].It was absorbed from the study that with increase in the rank of grit number, the wear response of fiber filled composites exhibits less wear volume loss, which eventually stabilizes to a constant value due to smaller and fine grain size of abrasives [7,29].This is in good agreement with the work of others [22,23,25,26].
The high wear volume loss of neat epoxy (EP) under the impact of 180 grit abrasive particles was due to the coarse and large size of the abrasive particles.Severe wear loss has been experienced by soft and low modulus neat epoxy under the impact of severe abrasion pressure.These abrasive particles exert intense pressure on the soft polymer matrix, penetrating it deeply.The large sized abrasive particles exert high contact stresses at the junction due to heavy penetration.Because of this there was a tendency for a significant wear volume loss [7,9,13].The low-modulus, soft plain epoxy became vulnerable to significant contact stresses as a result of abrasive grits' intense ploughing action, which resembled a pair of razor-sharp knives.The large sized abrasives exert high contact stresses and deep penetrations which caused the high wear volume loss [23,37].The effect of abrasion by the large sized particles was very much effective between the abrading distances of 25 m to 50 m.But later (> 50 m) the wear volume loss decreases due to clogging and ineffectiveness of abrasive particles.The interaction surfaces were agglomerated with the wear debris.The large sized abrasives have decreased the contact surface area between the abrasive grains and wear asperities by increasing the contact stresses at the junction.The extreme strain has been developed at the contact junction due to high pressure exerted by the large abrasive particles which tend to develop cracks that allowed for substantial wear volume loss in the material [22,34].When the grit number increases, the fine and smaller sized particles decreases the wear response of the same neat epoxy in terms of volume.At higher rank of grit number, less wear volume loss was observed due to fine and smaller size of abrasive particles.Their low contact stresses, which reduce the severity of penetration at the interaction junction [22].It was observed from the experiment that the wear response of polymer composites has become independent of grit number at higher rank of grit number.Therefore, less wear loss.
Each and every long jute and banana fibre filled epoxy composite exhibit a specific abrasive wear behaviour based on observations made on EP8, EP16, EP24, and EP32 composites.EP8 and EP16 composites showed the least amount of wear volume loss when subjected to various abrasive grits.This is superior to unfilled EP composites.Up to EP16 composites, the resistance to abrasion load has been maintained.The EP8 and EP16 composites show better wear resistance when subjected to various grit particles.This is because of the combined effect of jute and banana fibres.Further, their superior interaction with epoxy which was caused by high modulus EP16 composites made to control the wear loss.Wear volume loss was higher but better than other filled composites when 180 grit abrasion was applied to EP16 composites.This is due to the result of highcutting, sharpened teeth of abrasives digging up the matrix along with the fibres [22,23].These pointed abrasive particles have dragged the worn debris and broken fibers, exposing the jute fibres rough surface to the contact surface.In addition, banana fibres are brittle by nature, and when they are interacting with the abrasives, they supported the abrasive surface on the counter [5,7].This could increase the frictional force and result in more wear volume loss.But the excellent wear resistance of filled composites has been attributed to the Jute fibres which were structurally reactive with epoxy, resulting in the establishment of high strength polymer surface at the interface that may prevent wear loss [12,22].This can result in increased wear resistance.But the abrasion effect was severe up to 50 m of abrading distance.But later, due to clogging of the abrasive paper, down trend starts after 75 m up to 100 m.Here the abrasive paper was full of wear debris, broken fibers and clogged grains.This will reduce the effective area of interaction.The synergy of jute and banana, as well as wear debris from the matrix, has been dragged on to the abrasive surface, decreasing the effectiveness of abrasive grain penetration.
Further, the Ratner-Lancaster factor 'σε' is more for EP8 and EP16 composites respectively (table 4).Therefore, the abrasion wear resistance is directly proportional to (σε) [24,37].Hence, EP16 composites have higher wear resistance.However, as the rank of grit number was lowered, the effect of penetration was significantly reduced.
The wear volume loss was significantly impaired at the higher rank of grit, 600 Grit, and a stable value of wear loss was observed.At this condition, there was a transformation of abrasive wear to adhesive wear resulting in lower wear volume loss [23].Due to their efficient interaction with the abrasion load, the fine abrasive grains failed to abrade the hybrid fibres.Hence, less wear volume loss [4,5].The smooth and partial polymer film was developed on the abrasion surface filling the gap between the abrasive grains.This process is called clogging.This might lowered the wear loss of EP16 composites.EP16 composites exhibit the stronger abrasion wear resistance than other filled ones.However, low abrasion wear resistance has been observed as a result of higher loading of hybrid fibers following EP16 composites.
The EP24 and EP32 composites have shown a poor reaction.This may be due to the higher loading of natural fibers.Further, poor abrasion resistance exhibited by EP24 and EP32 composites may be due to their inferior mechanical properties, which would have controlled the wear loss.The inclusion of a higher percentage of fibers decreases the wear resistance by increasing the number of non-resin zones across the entire surface [25,35].Wear resistance may be lowered by the formation of cracks and loss of ductility by the stress concentration over non-resin zones.Additionally, for both EP24 and EP32 composites, the hardness and 'Hσε' factor were poor in fiber-filled composites, which may lowered the resistance to abrasive wear.Ratner [31] demonstrated that 'σε' factor directly correlates with the abrasion wear resistance of fiber filled composites.As a result, EP32 composites have less abrasion resistance.The abrasive action by the abrasive grains under 180 grit was supported by the broken fibers, ploughed worn debris and fatigue.Significant contact stresses were produced at the point of interaction when these abrasive particles were mixed together and rubbed against the polymer's surface.These have the ability to dig out the fibers from the soft polymer surface and cause a significant volumetric loss [31].But the abrasion wear behaviour of fiber filled composites having superior mechanical properties will retained their resistance even after 75 m of abrading distance.This could be possible due to ineffectiveness of abrasive grains due to over abrading of the abrasive paper.The investigated results are in good agreement with the work of others [37].
Figure 3(b) shows the 'Ks' of long jute and banana fibre reinforced epoxy composites under the impact of various SiC grit abrasive particles.It was seen from the representation that 'Ks' of composites under examination decreases as the rank of grit number increases.Under the effect of 180 grit, the Ks value of virgin epoxy (EP) was 57 ×10 −3 mm 3 N −1 -m −1 .When the impact of 600 grit on the neat epoxy (EP) was examined, it was noticed that decrease in wear rate of 27 ×10 −3 mm 3 / N-m which is around 53% decrease over 180 grit.The severity of the sharp abrasive grains increases the wear rate, however, decreases as the rank of grit number increases.Similar observations were noticed with other fiber filled composites.When compared to EP composites, it was found that the variation in wear rate between 180 and 600 grits was quite noticeable.Results revealed that the specific wear rates for EP8 and EP16 composites were 32 ×10 −3 to 11.5 × 10 −3 mm 3 N −1 -m −1 and 35 × 10 −3 to 14 × 10 −3 mm 3 N −1 -m −1 , respectively.Additionally, EP24 and EP32 composites, respectively, have demonstrated Ks of 48 × 10 −3 to 23 × 10 −3 mm 3 N −1 -m −1 and 40 × 10 −3 to 19 × 10 −3 mm 3 N −1 -m −1 over the range of examined grit geometry.
The considerable change in high wear rate was caused by the grits action of ploughing and crushing action, whereas the lesser wear rate was caused by finer size particles, decreased abrasivity and sensitivity [27,28].If we look at wear loss under the influence of 400 and 600 grit, we can see that both the situations have been stabilized in terms of wear loss.The surface of the composites was not possible to fracture by the abrasive particles which were smaller in sizes.Further, it was observed that under the action of finer grain size and smaller geometry of 600 Grit, the specific wear rate was independent of grit size.Therefore, stabilization of the wear loss has been occurred at these conditions.Because of their superior Ratner -Lancaster factor, EP16 composites showed a    effect of these abrasive grains was clearly observed as a result of deep penetrated soft matrix.The extensive plastic deformation has been caused which results in broad and deep wear tracks.The wear debris subjected to microcuttting is noticed on the surface.The repeated wear tracks are noticed which are results of impact of large abrasives with severe penetration at the wear junction.This caused a significant wear volume loss during abrasion.The abrasion effect of 180 grit abrasive on the worn surface of EP8 composites is demonstrated in the figure 5(b).However, due to the presence of natural fibres, mild and shallow wear tracks are observed on the worn surface of EP8 composites.The adhesion of the fibres with the matrix seemed to be good.These small and micro ploughed wear tracks are due to the combined effect of both banana and jute fibers which were effectively interacting with the epoxy.Here, the combination of crushed fibres and abrasive fillers results in microploughing actions which are noticed on the surface.Although the non-fiber zone was heavily strained, crack growth was prevented at fibre reinforced junctions.The wear debris due to micro actions was observed on the surface.The high toughened banana fibre when rub against the abrasive particles, the wear debris of banana fibre gets agglomerated at the interaction junction and made the counter surface partially abrasive.The deep ploughing has been prevented due to the presence of these jute and banana fibres.Therefore, wear loss has been prevented.
The SEM image of EP16 composites, however, shows a ductile and extremely shallow surface (figure 5(c)).Here the excellent adhesion of fibres with the matrix was observed.Here the fibres were ploughed along the matrix due to heavy abrasion action and their impressions were seen through deformation.The fibres were not broken down, crushed, ploughed, or micro-cutting in this instance.But the synergy of the banana and jute fibres led to the plastic deformation that was visible.In the figure, good fibre and matrix interaction is clearly demonstrated.Additionally, both fibres and the matrix adhesive strength allowed them to withstand the abrasion load during abrasion [22,35].The high compatibility between the fibres and matrix is exhibited by the homogeneous polymer surface.Furthermore, the pulverised particles behave as fillers rather than abrasives when the banana fibres are crushed under abrasion pressure.The polymer film will become stronger as a result, improving wear resistance.
Figures 6(a) and (b) depicts the SEM images of the worn surface morphology of EP24 and EP32 composites when they have been exposed to 10 N and 180 Grit SiC abrasives.The abraded surface of EP24 composites is shown in figure 6 (a).The figure shows the numerous cracks have been developed as a result of non-resin zones.More stress concentration zones caused the easier crack propagation.On the surface, there are also deep, wide worn tracks to be noticed.There were clumps of wear debris all across the contact zones.Due to loose packing of fibres in matrix, inappropriate rubbing results in transverse cracks.This has led to high wear volume loss compared to other filled composites.But the effect of the same on EP32 composite is shown in the SEM image (figure 6(b)).Because both the interacting surfaces were abrasive, EP32 composites exhibit the compatible behaviour.The blunt surface is caused by the high frictional force from the abrasive nature of surface and large sized abrasive particles.When banana fibre is crushed with abrasive particles, long uniform patches are produced [25,36].Due to uneven matrix association, deep plastic deformation is noticed.This has been experienced in the presence of hybrid fibers.Large deep wear tracks are seen as result of deep penetration.The presence of non-resin zones leads to heavier cracks across the surface.Therefore, less wear resistance has been exhibited by EP32 composites than other composites.It was observed from the surface morphology that microcutting, fatigue, micro-ploughing, and fibre pulverization were some of the failure mechanisms.

Specific wear rate as a function of mechanical properties
Some mechanical properties have a significant impact on the abrasive wear behavior of epoxy composites reinforced with natural fiber.The tensile strength (σ), percentage elongation (ε), hardness (H) and fracture energy (σε) are some of the mechanical properties which are influencing the wear behaviour of natural composites under two body abrasive wear mode.The main purpose of reinforcing fibers in to polymers is to increases the strength by the expense of its ductility.The two body abrasion wear behavior of fiber filled composites has been defined by the abrasive wear models.They postulated that abrasion wear resistance purely depends on the factors H, 'σε' and 'Hσε' [32,33].The tribological losses under the influence of room temperature have been defined by these factors.They stated that wear resistance has been correlated to specific wear rate based on the aforementioned factors which are responsible for the promotion of abrasion wear resistance.The specific wear rate as a function of some of the mechanical properties under a specific condition is shown in the figure 7(a)-(c).It is proved from the research bench that 'Ks' of composites investigated is inversely varies as the function of 'σε' from the postulates of Ratner et al [23].According to Yamaguchi's research, volumetric loss is a linear function of the product of load and the distance [37].Horst Czichos looked into how rupture stress affects the amount of abrasive wear [39].All of the epoxy-based composites that were tested during investigation adhered to the aforesaid ideas based on the abrasion wear models.Figure 7 (a)-(c) shows how the specific wear rate varies depending on a few mechanical characteristics.Nearly a linear relationship between the wear rate and mechanical parameters has been found from the abrasive wear response of all the composites examined.The wear rate which is shown in figure 7(a) is a function of rupture stress and rupture strain.It was established that EP16 composites displayed superior wear resistance and better rupture stress [30].
EP16 composites showed that the volumetric loss varied inversely with its rupture stress.For EP16 composites compared to all other materials, the factor 'σε' is better which is promoting factor for increasing the abrasion wear resistance [23].Furthermore, the Yamaguchi factor (PD), which is the result of product of load and the abrading distance, directly affects the volumetric loss of natural composites.It has been established that the wear rate for EP16 composites is proportionate to 'σε' which will have high abrasion wear resistance.But Ks of these composite was lowered because of lesser 1/σε and 1/ Hσε (figures 7(b) and (c)).But the specific wear rate of other filled composites, EP8, EP24, EP32 composites followed the same trends as that of EP16 composites.For neat EP, lesser 'σε' and higher 1/σε and 1/ Hσε which have led to exhibit high specific wear rate and least wear resistance.As a result, the abrasion wear behaviour of epoxy-based natural composites matches the models of abrasion wear.Further, the experiments have demonstrated that the composite materials with a higher volume fraction of fibers have poorer abrasion wear resistance [31,34].The similar finding was noticed among EP24 and EP32 composites.On the other hand, the abrasion wear resistance of PSU/SGF composite was increased when 30 weight percent of short glass fiber was reinforced to the base polymer PSU [24].In supporting to this, EP16 composites has exhibited the better wear resistance.This is in good agreement with the work of others [25,32,33,38].

Conclusion
The investigation into the impact of grit number and their particle size on the abrasion wear behaviour of epoxybased natural composites led to some significant findings.Long jute and banana hybrid fiber reinforced epoxy natural composites have the optimum abrasion wear response in controlling the wear loss due to abrasion.The 180 grit abrasion particles have shown increased wear volume loss, while 600 SiC grit has shown poorer response.Neat epoxy composites exhibit the poor abrasion wear resistance.EP24 and EP32 composites respond with least wear resistance among filled composites whereas EP16 composites exhibit the better wear resistance.It was observed that wear was abrasive at 180 grit but later it was transferred to adhesive at lower rank of grit.This is due to the coarse and higher grain size of 180 grit and fine and smaller grain size of 600 grit.At lower fine grain size of abrasives, the wear volume loss is independent of grit size.The failure mechanisms observed were microcutting, microploughing and pulverization of fibers.

Figure 1 .
Figure 1.Experimental set up used for processing composites: (a) Resin block with fibers, (b) Marking pattern as per ASTM dimensions on the fabricated plate and (c) ASTM specimens for different tests.

Figure 2 .
Figure 2. Experimental set up used for two body abrasive wear test (ASTM G99): (a) Specimen dimension along with pin and counter surface dimensions and (b) Schematic diagram of Pin on disc machine.

Figure 3 .
Figure 3. Two body abrasive wear behaviour of epoxy-based jute-banana natural composites under the effect of varying Grit: (a) Wear volume and (b) Specific wear rate.

2 .
56 × 10 −5 5.57 × 10 −5 better wear rate[31].The sequence of the abrasive wear resistance was EP16 > EP8 > EP32 > EP24 > EP.This demonstrated that natural fibres could exhibit wear resistance up to a predetermined volume fraction.The orientation and compatibility of EP 32 and EP 24 composites are shown in figure4.Figures5(a)-(c) shows the SEM image of the worn surface of neat epoxy under the impact of 180 grit SiC abrasive particles under the applied abrasion load of 10 N over a distance of 100 m at a speed of 1 m s −1 .Figure5(a) shows the worn surface of neat epoxy (EP) under the action of 180 Grit abrasives.The deep penetrated and wide wear tracks are observed on the surface.This is due to large sized abrasive particles.The

Figure 5 .
Figure 5. SEM picture of the abraded surfaces under the action 180 SiC Grit at a load of 10 N through 100 m: (a) EP composites, (b) EP8 Composites and (c) EP16 composites.

Figure 4 .
Figure 4. SEM image showing the orientation and compatibility of long fibers with matrix: (a) EP32 composites and (b) EP 24 composites.

Figure 6 .
Figure 6.SEM picture of the abraded surfaces under the action of 180 SiC Grit at a load of 10 N through 100 m: (a) EP24 composites and (c) EP32 composites.

Table 1 .
Information on the materials used in the manufacture of composites.

Table 2 .
Formulations of natural composites used for processing in weight fraction percentage.

Table 3 .
Density details of the developed composites.

Table 4 .
Factors responsible for the promotion of abrasion wear resistance.