EFFECT OF INGREDIENTS ON MECHANICAL AND TRIBOLOGICAL CHARACTERISTICS OF ... · EFFECT OF INGREDIENTS ON MECHANICAL AND TRIBOLOGICAL CHARACTERISTICS OF DIFFERENT BRAKE LINER MATERIALS

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Int. J. Mech. Eng. & Rob. Res. 2012 M P Natarajan et al., 2012

EFFECT OF INGREDIENTS ON MECHANICALAND TRIBOLOGICAL CHARACTERISTICS OF

DIFFERENT BRAKE LINER MATERIALSM P Natarajan1*, B Rajmohan2 and S Devarajulu3

*Corresponding Author: M P Natarajan,[email protected]

Asbestos possesses properties that are ideally suitable for use as a friction material in automotiveand a number of other applications. Animal and human studies carried out since the early 1900shave established that asbestos is carcinogenic and that exposure to especially asbestos dustcauses a large number of diseases. The search is, therefore, still on to find suitable substitutesfor asbestos. A brake lining containing 14 ingredients was investigated to study the effect ofingredients on various aspects of friction properties. The composite was developed for a non-asbestos organic based friction material for an automotive brake system and contained typicalingredients for commercial brake friction materials. Two types of friction materials with differentcombinations were developed: (1) flyash range (10%-60%), and (2) without flyash based frictionmaterials were investigated to study the effect of ingredients on the friction characteristics andwear. The main focus on the average normal coefficient, hot coefficient (Fade and recovery),wear loss, mechanical, as the function of the relative amount of the ingredient. The results alsoshowed that the friction coefficient of fly-ash was better in the range of 0.35 to 0.48 whencompared barites based brake linings and asbestos based brake linings. The materials such aspotassium titanate (terraces), wollastonite, friction dust powder have strongly influence on frictioncoefficient. Wear resistance of the friction material was strongly affected by the relative amountsof ceramic wool, rockwool, calcium hydroxide, and zircon. The presence of glass fiber, twaronfiber, has increased the strength of the friction material. All these samples were tested on chasetype friction tester at automobile ancillary unit.

Keywords: Flyash, Braking lining material, Chase type friction tester, Mechanical, Friction,Wear

INTRODUCTIONFlyash is a by-product of thermal powerstations. Much of the flyash is presently treated

ISSN 2278 – 0149 www.ijmerr.comVol. 1, No. 2, July 2012

© 2012 IJMERR. All Rights Reserved

Int. J. Mech. Eng. & Rob. Res. 2012

1 Department of Mechanical Engineering, Jerusalem College of Engineering, Chennai, India.2 Department of Production Technology, Anna University, Chennai, India.3 Rane Brake linings, Chennai, India.

as a waste product for uses such as land fillalthough a small quantity is utilized as fillers inconcrete, bricks and other materials.

Research Paper

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Nowadays attempts has been made to utilizeflyash in manufacturing sectors where largevolume usage of the same could be exploitedwill prove substantially beneficial in techno-commercial and environmental terms Flyashis composed of fine size particles (mean size10-30 mm), with uniform physical andengineering characteristics. Flyash possesseslow specific gravity in the range of 2-3, ascompared to ingredients used in contemporarybrake linings (Samrat and Chugh, 2007).Flyash particles are typically generated at veryhigh temperatures, i.e., 100 °C upwards.Hence, they should provide a thermally stablebulk for high-temperature environments that afriction composite experiences. Also, majorityof flyashes contain substantial amounts ofsilica, alumina, calcium sulfate and un-burntcarbon in them, which are already being usedin many of current commercial brake linings.The specific heat of flyash particles is also high(800 kJ/kg K). The successful incorporationof flyash or flyash derivatives into frictionmaterial formulations could greatly reduce thecost of the friction material, i.e., 50-60%assuming all the fillers are substituted (Samratand Chugh, 2007; and Nandan et al., 2009).Hence, incorporation of flyash would possiblycater to various functional roles whichotherwise are expected from a set of fillers asingredients. The purpose of friction brakes isto decelerate a vehicle by transforming thekinetic energy of the vehicle to heat, via frictionand dissipating that heat to the surroundings.The temperature sensitivity of friction materialshas always been a critical aspect whileensuring their smooth and reliable functioningof the brakes. High friction materials haveapplications in automotive, aerospace andindustrial brake systems. High friction

compositions are a three-elementcomposition consisting of a matrix ofpolymeric blends, reinforcing material, frictionand anti-wear material. Among the most wellknown polymeric systems known, the phenolicresins or modified phenolic resins are the wellknown thermo sets with good thermal stability.Friction materials for a brake system shouldbe designed to maintain stable and reliablefriction force at wide ranges of pressure,vehicle speed, drum temperature, humidityand others. No single material has met theperformance related criteria such as safety,noise propensity, durability and comfort undervarious braking conditions. In general, morethan 14 ingredients have been used forcommercial brake friction material toaccomplish above mentioned requirements.The friction materials have been formulatedbased on application such as light motorvehicle, light commercial vehicle and heavyduty vehicle and the ingredients comprise offillers, binders, fibers, solid lubricants andfriction modifiers and abrasive (Seong and Ho,2000; Min and Seong, 2005; and Yun and Min,2008). In this study an attempt has been madeto incorporate flyash in the brake liner for theeffective brake application for the light motorvehicle.

EXPERIMENTS

Friction Materials

Friction materials investigated in this studywere Non-Asbestos Organic (NAO) typematerials containing 14 different ingredientsas shown in the Table 1. Figure 1 showsconventional compression molding machineused for making friction material. Figure 2shows the procedure for making non asbestos

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Description (%) wt Composition %

Flyash 10-60

Filles 5-15

Friction Modifiers 15-25

Fibers 5-15

Binder 15

Lubricant 3-9

Table 1: Material Compositionfor Flyash Based Brake Liner

Figure 1: Compression Molding Machinewith a Steel Die

friction material. The ingredients in the frictionmaterial comprise binder resin, reinforcingfibers, friction modifiers, solid lubricants asgraphite (Kato, 2000). These ingredients wereweighed in given proportions, blended well,molded in a steel die and then heat treatmentprocess was carried out with the givenparameters. The each quantity of ingredientswas measured in the electronic scale andpoured into the mixer for mixing. The mixingtime was 15 min. After mixing, the mixture wastaken out of the mixer and required quantity ofmixture of 220 gm was measured and kept inthe die for pressing. The die was preheatedto 145 °C and pressure of 160 kg/cm2 wasapplied over a powder for a molding time of6 min (Table 2). The Friction material sampleof size 105 mm 130 mm 30 mm was made.

Figure 2: Procedure for Making NonAsbestos Organic Brake Lining

Mixing - 15 min

PreformPressure = 108 Kg/cm2

PressingPressure = 160 Kg/cm2

Temperature = 140 °C

Post CuringTemperature = 140 °C-150° C

Time = 8-12 hrs

Finishing

Specimen Preparation

TestingHardness, Friction and Wear

(Chase Type)

SEM, EDX

Thermal AnalysisTGA/DSC

Comparing the Results

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Asbestos Fiber Based FrictionalMaterial

The brake is an important safety device inmachines. The friction material is an essentialpart in brake and clutch devices. Different typesof brake materials are used in differentmachines Traditionally, these friction materialscontain chrysotile asbestos fiber as one of themajor constituents to impart the desiredcharacteristics. There is an importantdistinction to be made between serpentineand amphibole asbestos due to differencesin their chemical composition and their degreeof potency as a health hazard when inhaled.However asbestos and all commercial formsof asbestos (including chrysotile asbestos) areknown to be human carcinogens based onsufficient evidence of carcinogenicity in human.The materials that are used for automotivebrake lining applications, in particular, arebased on asbestos, and are used incombination with a number of otheringredients. Asbestos is a cheap and easilyavailable raw material. It is used extensivelyas lagging material, insulation material, rawmaterial for making corrugated sheet and aslining material (Sampath, 2006). It is also usedas reinforcement in the form of fiber, for makingcomposite material. Due to its good thermalstability and high L/D ratio, it is the mostprominent candidate for use as friction material

where thermal stability is important criteria.Asbestos became increasingly popular amongmanufacturers and builders in the late 19thcentury because of its sound absorption,average tensile strength, and its resistance toheat, electrical and chemical damage. It wasused in such applications as electricalinsulation for hotplate wiring and in buildinginsulation. Asbestos materials becomedangerous when a product’s integrity iscompromised due to external agents like heat,water, weathering and aging and fibers arereleased in to the environment. The fiberscontinue to break in to smaller and smallerparticles. The asbestos fibers are having20 to 500 micron length and 0.5 to 50 microndiameter. The small size and lightweight of thefiber allow them to remain airborne for anextended period after initial release. The riskof asbestos-related disease increases withheavier exposure to asbestos and longerexposure time. Asbestos had a fewengineering characteristics that made it verydesirable for inclusion in brake linings.Asbestos is thermally stable up to 500 °C, ithelps regenerate friction surface during use, itinsulates thermally, it is strong and flexible and,mostly, it is available cheap. Since the ban onasbestos, researchers have struggled to comeup with an equally efficient alternative

Flyash Based Frictional Material

The combustion of powdered coal in thermalpower plants produces flyash.The hightemperature of burning coal turns the clayminerals present in the coal powder into fusedfine particles mainly comprising aluminiumsilicate. Flyash produced thus possesses bothceramic and pozzolanic properties. Flyashmaterial solidifies while suspended in the

Parameter/Level Level 1

Pressure (Kg/cm2) 160

Temperature °C 140

Time (min) 4-6

Curing Temperature °C 155

Curing Time hrs 8-12

Table 2: Process Parameters

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exhaust gases and is collected by electrostaticprecipitators or filter bags. Since the particlessolidify while suspended in the exhaust gases,flyash particles are generally spherical in shapeand range in size from 0.5 µm to100 µm.Flyash possesses low specific gravityin the range of 2-3, as compared to ingredientsused in contemporary brake linings (Samratand Chugh, 2007). Flyash particles are typicallygenerated at very high temperatures, i.e.,1000 1C upwards. Hence, they should providea thermally stable bulk for high-temperatureenvironments that a friction compositeexperiences. The specific heat of flyashparticles is also high (800 kJ/kg K). Thesuccessful incorporation of flyash or flyashderivatives into friction material formulationscould greatly reduce the cost of the frictionmaterial, i.e., 50-60% assuming all the fillersare substituted (Nandan et al., 2009). Also,majority of flyashes contain substantialamounts of silica, alumina, calcium sulfate andunburnt carbon in them, which are alreadybeing used in many of current commercialbrake linings. Much of the flyash is presentlytreated as a waste product for uses such asland fill although a small quantity is utilized asfillers in concrete and other materials. Attemptsto utilize flyash in manufacturing sectors wherelarge volume usage of the same could beexploited will prove substantially beneficial intechno-commercial and environmental terms.Hence, incorporation of flyash would possiblycater to various functional roles whichotherwise are expected from a set of fillers asingredients. In this study an attempt has beenmade to incorporate flyash in the brake linerfor the effective brake application for the lightmotor vehicle.

Measurement of Friction and WearCharacteristics

Friction and wear tests were conducted usinga Chase-type friction tester with grey cast ironas the counterpart with a 280 mm diameterand a hardness of 210 HB, according SAEJ661test procedure. Figure 3 shows theflyash based friction material used testingpurpose.

Measurement of PhysicalProperties

Hardness, Porosity, tensile strength, wascarried out in accordance with the ASTMD638. Rockwell hardness tester with a ballindenter was used for measuring the hardnessof the brake pads machined out of the frictioncomposites. Tensile specimen has a constantrectangular 115 mm 25 mm 14 mm.

RESULTS AND DISCUSSIONEffect of Ingredients on PhysicalProperties

Physical properties hardness, porosity andtensile strength of the friction materialspecimens were measured from flyashbased composites and barites basedcomposites. The mechanical propertystudies were carried out to find out the

Figure 3: Frictional Material Usedfor Testing Purpose

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suitability of the composites for brake liningapplications. The presence of fibers in thephenolic matrix improves the hardness andtensile, this is expected, since the hard fibersreinforce the soft resin matrix.

The hardness, tensile strengths are theparameters that contribute significantly to thefrictional behavior of the composites andthese composites were found to exhibit goodmechanical properties. Figures 4, 5, 6 and 7

Figure 4: Samples vs Hardness of Flyash with Different Percentage of MolybdenumDisulphide Based Friction Material Molded at Temperature 140 °C, Time 4 min,

Pressure 160 kg/cm2

Figure 5: Samples vs Hardness of Flyash with Different Percentage of MolybdenumDisulphide Based Friction Material Moulded at Temperature 140 °C, Time 6 min,

Pressure 160 kg/cm2

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exhibits correlation among the hardness offlyash and barites based friction materialunder constant temperature and constantpressure for the molding of time 4 min and6 min. Figures 8 and 9 shows that the strengthof flyash based friction materials exhibit lowdue to increase of percentage of filler materials

and low percentage of fibers. The figure clearlyindicates that the specimens with highhardness tend to exhibit low porosity. The lowtensile strengths of the composites areattributed to the high filler content and thefibers being short in length. The Figures 10and 11 shows the tensile strength of barites

Figure 6: Samples vs Hardness of Barites (Without Flyash) with 9%, 6% and 3%Molybdenum Disulphide Based Friction Material Moulded at Temperature 140 °C,

Time 4 min, Pressure 160 kg/cm2

Figure 7: Samples vs Hardness of Barites (Without Flyash) with Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,


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based friction material were higher due toaddition of twaron 1080 (aramid fiber), glassfiber which increases the strength of thecomposite.

Figure 8: Samples vs Tensile Strength of Flyash with Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,


Figure 9: Samples vs Tensile Strength of Flyash with Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,


The high hardness from the increase ofphenolic resin is due to the fact that the binderresin is a thermosetting polymer showing highstrength after curing. On the other hand,

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films. Cashew particles also reduced thehardness since this polymeric material doesnot play a particular role for the enhancementof strength of a composite. The presence ofpotassium titanate particular powder,

potassium titanate and cashew have contraryeffects on hardness. This is because thepotassium titanate is in the shape of fineparticulate. However, the potassium titanateplays a crucial role in the formation of friction

Figure 10: Samples vs Tensile Strength of Barites (Without Flyash) Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,


Figure 11: Samples vs Tensile Strength of Barites (Without Flyash) with Differenentof Molybdenum Disulphide Based Friction Material Moulded at Temperature 140 °C,

Time 6min, Pressure 160 kg/cm2

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wollastonite, phenolic resin increases inhardness of composite decreases the porosityof the composite. Porosity was increased withE-glass fiber, ceramic wool, rock wool andcashew dust powder, suggesting that these

ingredients did not flow during hot molding asshown in the Figures 12 and 13. Phenolic resinreduced porosity since the resin ran and filledthe pores during hot molding. The Figure 12shows that friction material was molded with

Figure 12: Samples vs Porosity of Barites (Without Flyash) with Different Percentageof Molybdenum Disulphide Based Friction Material Moulded at Temperature 140 °C,


Figure 13: Samples vs Porosity of Barites (Without Flyash) Different Percentageof Molybdenum Disulphide Based Friction Material Moulded at Temperature 140 °C,


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molding time 4 min, since molding time wasinsufficient for the resin to flow uniformlythrough out the friction material therebyincrease in porosity of the friction material.Figure 13 shows that increase in molding from4 min to 6 min had significant decrease inporosity and increase in tensile strength sincefills the porous holes in the friction material.

Effect of Ingredients on Frictionand Wear Characteristics

A study of the literature pertaining to wear/failure mechanisms of friction materialsreveals that there are at least four or moredifferent failure modes operating duringbraking: adhesive wear, abrasive wear,chemical wear, fatigue wear, thermoinstability,and microcracks (Ho, 1977; Liblisch andRhee, 1977; Talib et al., 1977; Azhari andTalib, 1998; and Vaziri et al., 1988). The rateof wear and the coefficient of friction offriction materials are very important

parameters for selection, since they decidethe suitability of the materials for brake liningapplications. It is the fibers that add to thewear resistance and the coefficient of friction.When the fibers are removed from the matrixby pull-out or abrasion. Even though manyresearchers have worked on the wearmechanisms in friction materials, still not muchis known as to what happens exactly in thematerial process zone of the brake system. Itis proposed that third body layers develop(Kato, 2000; and Filip et al., 2002). Theselayers have compositions different from thoseof the mating parts. Many researcherspointed out that the formation of a friction filmby wear debris compaction plays animportant role in stabilizing the coefficient offriction (Rhee and Ludema, 1978). The baritesbased and flyash based friction material weretested in the chase type friction test rig andthe average of coefficient of friction of normal

(a) Samples vs Average COF of Barites (Without Flyash)

Figure 14: Samples vs Average COF of Barites (Without Flyash) with DifferentPercentage of Molybdenum Disulphide Based Friction Material Moulded

at Temperature 140 °C, Time 4 min, Pressure 160 kg/cm2

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mu, Hot mu and wear of these compositeswere measured. The phenolic resin,wollastonoite and cashew increase thecoefficient of friction and potassium titanatezircon, and rubber decrease the frictioncoefficient. The Figures 14 and 15 shows thecoefficient of friction of barites (without flyash)

molded at different time of 4 min and 6 minunder uniform molding temperature andpressure. The Figures 16 and 17 shows thatthe coefficient of friction of flyash basedfriction materials were lower when compareto non flyash based friction material due tohigher amount of fillers and solid lubricants.

(b) Samples vs Average COF of Barites (Without Flyash)

Figure 14 (Cont.)

(c) Samples vs Average COF of Barites (Without Flyash)

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(a) Samples vs Average COF of Barites

Figure 15: Samples vs Average COF of Barites (Without Flyash) with DifferentPercentage of Molybdenum Disulphide Based Friction Material Molded

at Temperature 140 °C, Time 6 min, Pressure 160 kg/cm2

(b) Samples vs Average COF of Barites

(c) Samples vs Average COF of Barites

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(a) Coefficient of Friction vs Samples

Figure 16: Coefficient of Friction vs Samples of Flyash with Different Percentageof Molybdenum Disulphide Based Friction Molded at Temperature 140 °C, Time 4 min,

Pressure 160 Kg/cm2

(b) Coefficient of Friction vs Samples

(c) Coefficient of Friction vs Samples

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(a) Coefficient of Friction vs Samples

Figure 17: Coefficient of Friction vs Samples of Flyash with 9%, 6% and 3%Molybdenum Disulphide Based Friction Molded at Temperature 140 °C, Time 6 min,

Pressure 160 Kg/cm2

(b) Coefficient of Friction vs Samples

(c) Coefficient of Friction vs Samples

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The change of the coefficient of friction isclosely related to the hardness andmorphological feature of each ingredient.Therefore, the ingredients with high hardnesssuch as phenolic resin, and cashew increasethe coefficient of friction due to abrasive actionagainst the cast iron brake drum. The COFincreases relative to the amount of cashewdust, wollastonite, barites added to thesamples. From the Figure 15 indicates thatincrease in molding time from 4 min to 6 minhad significantly improved in friction coefficient.Wear of barites (without flyash) based frictionmaterial lower due to addition of potassiumtitanate, wollasnoite, to the samples.

Alternately, the increase in addition of otherfiller ingredients vermiculite, mica can resultin low COF. Figures 18 and 19 shows thewear of flyash based friction material moldedat different time of 4 min and 6 min. The wearwas higher n due to insufficient molding timeand increase in percentage of fillers such as

flyash, vermiculite, mica, hydrated limepowder in friction material FM-1, FM-2, FM-3, FM-4, FM-5 and FM 6 when compared towear of the Barites based frictional materialB-1, B-2, B-3, B-4 and B-5 usage ofpotassium titanate (terraces), Twaron 1080(Aramid Fiber) in the composite, increasesthe coefficient of friction and generally not inusage due to high cost.

It may viable to be used in the heavy vehiclebrake lineras shown in Figures 20 and 21.From the figure it can seen that lower amountof molybdenum disulphide shows better resultswhen the higher amount of molybdenumdisulphide. The increase in percentages ofmolybdenum disulphide from 3% to 9%reduces the hardness of friction material andincreases wear of the friction material. Thelowering of the friction level due to zircon isalso attributed to the morphological effect. Ingeneral, zircon particles are used to eithercontrol the friction level or clean the pyrolized

Figure18: Samples vs Wear of Flyash with Different Percentage of MolybdenumDisulphide Based Friction Material Moulded at Temperature 140 °C, Time 4 min,

Pressure 160 kg/cm2

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friction film. Coarse zircon (Yuning andGraz¡yna, 2008) particles are normally usedto control the friction level and fine zircon flouris used to remove the friction film. However,zircon can improve negative wear rate caused

by either gas release or thermal expansion ofthe nonmetallic friction materials. The wear rateof barites(without flyash) friction materials withzircon is larger than that of without zircon asshown in the Figures 20 and 21.

Figure 19: Samples vs Wear of Flyash with Different Percentage of MolybdenumDisulphide Based Friction Material Moulded at Temperature 140 °C, Time 6 min,

Pressure 160 kg/cm2

Figure 20: Samples vs Wear of Barites (Without Flyash) with Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,


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Figure 22 shows the composite containingflyash 60% with abrasive, fillers, fibers and

friction modifiers such as cashew dust powders,potassium titanate (terraces) and wollastonite.

Figure 21: Samples vs Wear of Barites (Without Flyash) with Different Percentageof Molybdenum Disulphide Based Friction Material Molded at Temperature 140 °C,

The Figure 23 shows the compositecontaining abrasive, fillers, fibers and frictionmodifiers such as cashew dust powders,potassium titanate (terraces) and wollastonite.

Figure 24 shows the EDX of FM-1 samplewith different material composition used formaking friction material. The presence ofsilicon, ferrous and oxides in the flyash

Figure 22: SEM Image of FM-6

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potassium titanate, wollastonite and Bariumsulphate in the material composition that hasbeen highly influenced to increase thecoefficient of friction and wear to decrease.

Figure 25 shows the EDX of B-1 (withoutflyash) sample with different materialcomposition used for making friction material.

Since the percentage of fillers has increasedto a higher amount and to maintain thecoefficient of friction to an optimum level. Theothers materials such as , E- glass fiber, twaron1080 (Aramid fiber) barium sulfate andpotassium titanate, zircon that are added tothe friction material.

Figure 23: SEM Image of B-1

Figure 24: EDX of FM-1

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Figure 25: EDX of B-1

Figures 26 and 27 the coefficient of frictionkeeps on changing when the number of brakeapplications was increased, this is due towhen drum temperature was increasedbeyond 250 °C the morphological changesoccurs in each ingredients and it was closely

related to the hardness, therefore, theingredients with low melting point degraded

and lose its bits bonding strength as a resultthe coefficient of friction decreases.

Figure 28 the coefficient of friction changeswhen the number of brake applications wasincreased, this is due to morphologicalfeature of each ingredients and closelyrelated to the hardness. Therefore, theingredients with high hardness such as

Figure 26: Number of Brake Application vs Coefficient of Friction of FM-1

0 10 20 30 40 50 60 70 80 90 100

Apps.

1.0

0.8

0.6

0.4

0.2

0.0

Fri

ctio

n

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modified phenolic resin, and cashew increasethe coefficient of friction due to abrasiveaction against the cast iron brake drum.

ACKNOWLEDGMENTAuthors gratefully acknowledge the support ofJai Brakes, Chennai and Rane Brake liningsLimited, Chennai, India for their help in makingfriction materials and conducting friction andwear test.

CONCLUSION• The increase in percentage of flyash

reduces coefficient of friction and also andthe weight of brake liner and it is suitablefor light motor vehicle.

• In the flyash based frictional material, theCOF were moderate and wear losses werehigh. However in the case of non flyashfrictional material, it was observed that the

Figure 27: Number of Brake Application vs Coefficient of Friction of FM-6

0 10 20 30 40 50 60 70 80 90 100

Apps.

1.0

0.8

0.6

0.4

0.2

0.0

Fri

ctio

n

Figure 28: Number of Brake Application vs Coefficient of Friction of B-1

0 10 20 30 40 50 60 70 80 90 100

Apps.

1.0

0.8

0.6

0.4

0.0

Fri

ctio

n

0.2

156


COF were too high and the wear losseswere minimum. The wear resistance andcoefficient of friction was significantlyimproved by addition of Twaron 1080 Fiber,Wollastonite and ceramic wool.

• The presence of potassium titanateparticular powder, wollastonite, phenolicresin, and zircon increases in hardness ofcomposite and decreases the porosity ofthe composite. The hardness has stronginfluence on porosity which reduces thewear of the friction material.

• Increases in percentage of rubber powder,vermiculite and cashew friction dust powderreduce the hardness of the sample andincreases the porosity of the samples.Increase in molding time 4 min to 6 min hasimproved in performance of friction material.

• It was observed that the tensile strength offlyash friction material was lower than thebarites friction material. The low tensilestrengths of the composites are attributedto the high filler content and low fiber contentin the friction material also due to short inlength of fiber.

• Addition of abrasive powder to the sampleF2, F4 and F6 increase hardness of thefriction material. The usage of potassiumtitanate (terraces), Twaron 1080 (AramidFiber) in the composite, increases thecoefficient of friction and generally not inusage due to high cost. It may viable to beused in the heavy vehicle brake liner.

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3. Filip P, Weiss Z and Rafaja D (2002),“On Fr ict ion Layer Format ion inPolymer Matrix Composite Materialsfor Brake Applications”, Wear, Vol. 252,pp. 189-198.

4. Ho T L (1977), “Proceedings of theInternational Conference on Wear ofMaterials”, pp. 70-76, St. Louis, MO, USA.

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EFFECT OF INGREDIENTS ON MECHANICAL AND TRIBOLOGICAL CHARACTERISTICS OF ... · EFFECT OF INGREDIENTS ON MECHANICAL AND TRIBOLOGICAL CHARACTERISTICS OF DIFFERENT BRAKE LINER MATERIALS