IJREAS Volume 2, Issue 5 (May 2012) ISSN: 2249-3905...

IJREAS Volume 2, Issue 5 (May 2012) ISSN: 2249-3905

International Journal of Research in Engineering & Applied Sciences 51

http://www.euroasiapub.org

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF FA-SBR

HYBRID COMPOSITES

Gope P. C.**

Verma Deepak*

Singh V.K.**

Sharma R. K*

Maheshwari M.K*

ABSTRACT

Composite material is the combination of two or more materials, which possess much

superior properties than any of the other individual material. In the present investigation a

Fly Ash (FA) - Styrene Butadiene Rubber (SBR) hybrid composite with Epoxy Resin (ER) as

parent material is developed. The FA percentage for the developed material is varied as 1 wt.

%, 2 wt. %, and 3 wt. %.Experimental results explored that with the increase in % of FA,

density of the material increases but further addition of FA and SBR it decreases.It has also

been found that the tensile strength of the hybrid composite material decreases with the

increase of FA content. Also the wear rate of the neat ER is very high. But with the addition

of FA wear rate of the composite is decreased initially but further addition of FA, increased

the wear rate. The microstructure of hybrid composite material is studied by using Scanning

Electron Microscope (SEM). The SEM demonstrated that the FA and SBR particles are

uniformly distributed over the matrix. It has also been found that Hybrid composite material

with higher FA content exhibit higher hardness.

Keywords: FA, SBR, ER, SEM, Hardness, tensile strength, wear rate.

*College of Engineering Roorkee, Roorkee, Uttarakhand

**Department of Mech. Engg., College of Technology, G. B. Pant University of Agri. &

Tech., Pantnagar




1. INTRODUCTION

The term composite originally arose in engineering, where two or more materials are

combined to rectify some short-coming of a particular useful component. Composite

represents a material system consisting of several phases of which at least one is a solid phase

with macroscopic perceivable boundaries and which makes it possible to obtain new

properties or a combination of properties not attainable by any of its components separately

or by their sum. The properties of composite materials depends upon the degree of

inhomogeneity, density of constituents, method of fabrication, orientation of fibers in case of

the fiber reinforced composites etc. Properties such as strength and toughness of composite

materials are not as well understood as the simpler elastic properties because in many cases

the modes of failure under a given system of external load are not predictable in advance.

Sombatsompop et al (2006) suggested that the tensile and flexural moduli of the composites

increased with increasing fly ash content while the effect became opposite for tensile, flexural

and impact strengths, and tensile strain at break. Ramakrishna et al (2006) prepared Granite

powder filled epoxy and polybutylene terephthalate (PBT) toughened epoxy composites. the

variation of the mechanical properties such as tensile, flexural, compressive strengths and

impact with filler content was evaluated. Alam et al (2006) attempted tofind out sustainable

use of fly ash generated from Barapukoria Power Plant. This is used as an admixture with

Special Cement in 5%, 10% and 15% proportion. Laboratory test for different parameters

such as compressive strength, workability, flexural strength, splitting tensile strength of such

mixtures are carried out to find out optimum content. Mahendra et al (2007) showed in his

investigation that an Al–4.5% Cu alloy was used as the matrix and fly ash as the filler

material. The composite was tested for fluidity, hardness, density, mechanical properties,

impact strength, dry sliding wear, slurry erosive wear, and corrosion. Microstructure

examination was done using a scanning electron microscope to obtain the distribution of fly

ash in the aluminium matrix. Prashanth et al (2007) studied that Aluminium Matrix

Composites (AMCs) refer to the class of light weight high performance Aluminium centric

material systems. Mechanical properties such as sliding wear, hardness and micro structural

analysis have been studied. Kamali et al (2007) evaluated the abrasion resistance of high

volume fly ash (HVFA) concretes made with 35, 45, 55, and 65% of cement replacement in

terms of its relation with compressive strength. Test results indicated that abrasion resistance

of concrete having cement replacement up to 35 percent was comparable to the normal

concrete mix without fly ash. Siddique et al (2008) carried out the effects of addition of




natural san fibres on the fracture toughness and impact strength of high-volume fly ash

concrete. Tests were performed for compressive strength, fracture toughness, and impact

strength. Satapathy et al (2008) showed thatcoatings of fly ash (an industrial waste) mixed

with illmenite (a low grade ore mineral) have been deposited on mild steel and copper

substrates using conventional atmospheric plasma spray technique. Micro-hardness

measurement, phase composition analysis, coating porosity measurement, and surface and

interface morphology are studied to characterize the coatings. Wichianbut et al (2005)

showed that tensile strength, elongation at break, tear resistance and abrasion resistance

decreased but hardness increased with increasing lignite FA loading. In the present

investigation a FA-SBR hybrid composite with ER as parent material is developed. The FA

percentages have been varied as 1 Wt. %, 2 Wt. %, and 3 Wt. % and SBR percentage is also

varied by .25 Wt. % and .5 Wt. % and determined the mechanical properties of the developed

composite.

NOMENCLATURE

CY230 Epoxy resin

HY951 Hardener

SBR Styrene butadiene rubber

FA Fly Ash

FCFA F class fly Ash

NDT Non-destructive test

DWT Disc wear tester

WT./WT. Weight to weight

SEM Scanning electron microscope

Ef Modulus of elasticity of filled composite

E0 Modulus of elasticity of unfilled composite

σu Ultimate Tensile Strength of filled composite

C0 0 wt. % FA and 0 wt. % rubber

C1 1wt. % FA filled epoxy composite

C2 2 wt. % FA filled epoxy composite

C3 3 wt. % FA filled epoxy composite

C4 1 wt. % FA and 0.25 wt. % rubber filled epoxy composite









2. DEVELOPMENT OF HYBRID COMPOSITE

The matrix system consists of ER (CY230) and corresponding hardener (HY951) supplied by

M/s CIBATUL Limited, India. Two types of fillers namely FA and SBR have been used. FA

is supplied from Century Paper and Pulp Industry Limited, Lal Kuan (India). FCFA consists

of high percentage of silica (52 Wt. %), alumina (26.20 Wt. %), and various compositions as

shown in Table 2.1. SBR is used as a secondary reinforcement.

Table 2.1 Compositions of Fly Ash

Composition Percentage

Silica 52.50

Alumina 26.20

Fe2O3 6.50

Titanium 1.28

CaO 1.12

Potassium Oxide 0.96

Mg and MgO 0.29

Na2O 0.29

Sulphates 0.34

Phosphates 0.05

Unburnt Coal 9.16

The primary reinforcing FA particles have been added at desired concentration (1%, 2%, and

3% wt /wt) in the ER and stirred for 20 minutes to ensure proper mixing of the materials. The

mixed material (FA and ER) is heated in the oven up to 100°C and mainta ined the same

temperature for one hour by keeping it in the oven itself. Then the mixed material (FA and

ER) is taken out from the oven and cooled to 45°C and hardener was added in 8% wt/wt

because of which a highly viscous solution has been obtained. This solution is properly

mixed by mechanical stirrer until its temperature came down to 40°C and poured into

different moulds. In similar way SBR is used as a secondary reinforcing element. A solvent

(NN Dimethyl Formamide) is used to make a SBR solution and then it is mixed mechanically

by stirrer. The mixed material (FA, SBR, and ER) is heated in the oven up to 100°C and

maintained the same temperature for one hour by keeping it in the oven itself. Then the

mixed material is taken out from the oven and cooled to 45°C and hardener was added in 8%

wt/wt because of which a highly viscous solution has been obtained. This solution is properly




mixed by mechanical stirrer until its temperature came down to 40°C and poured into vertical

mould box (perpex sheet) as shown in figure1.

3. TESTING METHODS

To determine density of developed composites with different concentrations, exactly one cm

cubes have been prepared and weighted in Digital Electronic Balance (DEB) which is having

least count of 0.0001gm. Tensile tests have been conducted by using tensile testing machine

(ADMET – 100KN) as shown in figure 2.Wear behavior were studied with the help of a pin

on Disc Wear Tester under constant load of 2 bar (108.18 N) and three different speeds 232

rpm, 322 rpm and 422 rpm. Configuration and geometry of specimen is shown in figure 3 and

4. The Rockwell hardness of the developed composite materials is carried on the P.S.I

Hardness testing machine (rubber and polymer) on C scale as shown in figure 5. The ball

indenter ½” (12.70 mm) diameter is selected as specified for polymer-polymer composites.

The ball indenters are generally made of hardened tool steel or tungsten carbide. In Rockwell

hardness test an indenter is first seated firmly in the material being tested by application of

minor load 10 kilograms. The scanning electron micrograph study generally performed by

Scanning Electron Microscope (SEM) which uses electron to form an image with high

resolution or magnification. The images are obtained through microscope investigation with

LEO435V6.




4. RESULTS AND DISCUSSION:

4.1. Density

Densities of different composites have been determined by DEB and the results are enlisted

in Table 4.1.




Table 4.1. Density of FA and SBR hybrid composite materials

Composition Density (Kg/m3 ) ×103

C0 1.1603

C1 1.3380

C2 1.3302

C3 1.2579

C4 1.3010

C5 1.1105

C6 1.1974

C7 1.1271

C8 1.3049

C9 1.2160

Above results explore the fact that increase in weight percent of FA particles in the solution

increases the density of composite up to certain extent but further addition of FA particles

decreases the density composite. This is due to the FA particles which are having some

hollow spherical particles called cenospheres, reduces the density of the composites as their

weight percentage increases in the composite. Addition of SBR has also been decreases the

density of composite as compare to composite containing FA only.

4.2. Tensile strength

Materials, which exhibit the largest strengths during tensile testing, have the lowest impact

values. Tensile modulus is an indication of the relative stiffness of the material, and can be

determined from the stress strain diagram. As the pull of the material is continued until it

breaks, a complete tensile profile is obtained. A curve will result showing how it reacts to the

forces being applied. The point of failure is of much interest and is typically called its

Ultimate Tensile Strength (UTS) on the chart. UTS (σu), modulus of elasticity (E) and yield

stress (σy)of the various developed composite materials namely C0, C1, C2, C3, C4, C5, C6, C7,

C8, and C9 have been found and the results are enlisted in Table 4.2.

Table 4.2. σu , E, and σy of developed composite materials

Composite Type σu (MPa) E (MPa) σy (MPa) % reduction of σu in

comparison with C0

C0 50.00 309.00 4.21 --

C1 35.18 575.95 9.89 29.64

C2 33.49 540.20 10.31 33.02

C3 32.14 514.97 8.91 35.72




C4 28.69 443.84 9.26 42.62

C5 27.42 444.64 8.22 45.16

C6 33.40 474.67 9.02 47.20 C7 18.36 339.19 7.53 63.28

C8 27.58 414.58 7.15 44.84

C9 31.33 476.42 10.31 47.34

From the above results it can be observed that the tensile strength of the FA filled epoxy

composites and FA-SBR hybrid composites decreases with increasing FA percentage (by

weight percent) in the matrix. In comparison with the tensile strength of neat epoxy (C 0),

tensile strengths of other developed composites had been reduced as shown Table 2. The

variation in σu, E, and σyof the various developed composite materials are shown in figure 6 –

8. From figure 6 UTS of FA - SBR hybrid composite is being reduced continuously up to 2

wt. % FA then it becomes almost constant for higher percentages of FA and so it may be

concluded that UTS is significant up to 2wt. % of FA composite. Figure 7 shows that

modulus of elasticity of the composites, first increases up to 1wt. % of FA then slightly

decreases and becomes almost constant for 2 wt. % and 3 wt. % FA composites. This is

because of the addition of FA into the rubber compounds resulted increase of filler network,

which restricted the movement of rubber molecules during dynamic deformation. This gives

rise to a higher elastic modulus of the composite. Hence modulus of elasticity of hybrid

composite is significant for 1wt. % FA composite. Figure 8shows that yield stress

continuously increases up to 1 wt. % FA composites then becomes almost constant. So yield

stress is significant for 1wt% hybrid composite. The stress - strain diagrams of different

developed composites are shown in figure 9-11.




4.3. Wear Rate

Wear behavior of FA filled epoxy composites and FA – SBR hybrid composite were studied

with the help of a pin on disc wear tester under constant load of 2 bar (108.18 N) and three

different speeds 232 rpm, 322 rpm and 422 rpm for different fractions of time. Observations

are listed in table 4.3(a), 4.3(b) and 4.3(c).

TABLE 4.3(a)

AT 232 RPM 0 SEC 30 SEC 60 SEC 90 SEC 120 SEC 150 SEC

C0 NA 56.93 70.93 78.01 84.81 NA

C1 NA 46.22 50.82 54.72 56.63 NA

C2 NA 51.15 56.94 58.14 63 NA

C3 NA 44.72 45.80 46.49 48.01 NA

C4 NA 47.31 50.11 53.84 61.41 NA

C5 NA 48.56 51.96 55.01 64.56 NA

C6 NA 46.76 51.82 53.62 60.40 NA

C7 NA 48.84 53.69 50.60 61.53 NA

C8 NA 46.21 48.56 52.68 56.38 NA

C9 NA 48.01 49.97 53.68 59.48 NA

TABLE 4.3(b)

AT 322 RPM 0 SEC 30 SEC 60 SEC 90 SEC 120 SEC 150 SEC

C0 NA 70.61 84.47 92.71 NA NA

C1 NA 46.63 48.15 56.63 59.48 NA

C2 NA 47.87 48.29 50.11 58.13 NA

C3 NA 45.94 46.49 47.59 50.11 NA




C4 NA 48.01 52.10 53.03 66.16 NA

C5 NA 48.99 53.55 56.19 67.77 NA

C6 NA 47.31 52.39 55.89 63.23 NA

C7 NA 49.01 54.46 57.38 66.77 NA

C8 NA 46.76 50.11 52.02 59.18 NA

C9 NA 46.21 50.82 54.28 60.86 NA

TABLE 4.3(c)

AT 422 RPM 0 SEC 30 SEC 60 SEC 90 SEC 120 SEC

C0 NA 72.55 86.90 93.06 NA

C1 NA 48.84 51.10 65.94 NA

C2 NA 45.53 49.12 61.40 NA

C3 NA 44.86 52,68 59.97 NA

C4 NA 50.82 52.97 67.08 NA

C5 NA 48.84 54.86 70.55 NA

C6 NA 48.15 51.67 64.41 NA

C7 NA 47.59 53.26 65.38 NA

C8 NA 47.67 49.42 56.79 NA

C9 NA 47.04 54.28 64.46 NA

Figure 12 – 14 shows the variation of wear rate with time (sec) for different FA – SBR hybrid

composites. Fig shows that initially wear rate is continuously increasing then become almost

constant and further increases in the different intervals of time. Figure 15 – 17 shows the

variation of wear rate with different speeds (232 rpm, 322 rpm and 422 rpm) for different FA

– SBR hybrid composites. Fig. shows that wear rate of hybrid composites are continuously

increasing by increasing the disc speeds.All the three phases are active in case of C1, C2 and

C3 FA filled composites. The presence of FA particles within the matrix resin also resists the

wear rate to a significant extent. In case of C1 and C2 composites; due to stronger

filler/matrix interaction, debonding at the interface was minimum. Hence most of the energy

was expended in material wear (both matrix and FA). Whereas by increasing the FA in C3

composites there is not so much good interaction between FA particle and matrix material as

compared to C1 and C2 composites; hence a part of the energy was expended in resin/filler

debonding at the interface and the rest was used for material wear and removal resulting a

lower wear loss.




4.4. Hardness

Hardness of a material is one of the major important mechanical properties. It may be defined

as the property of material by virtue of which it is able to resist abrasion, indentation (or

penetration) and scratching by harder body. The hardness of the composite material increases

by increasing the fly ash content.

Table 4.4 Hardness of Styrene butadiene rubber fly ash hybrid composite




S.NO C1 C2 C3 C4 C5 C6 C7 C8 C9

1. 122.55 124.54 126.61 120.66 119.24 121.98 121.16 122.61 121.55

2. 122.41 124.37 126.89 120.57 120.36 122.61 122.57 123.74 122.05

3. 122.45 124.63 127.21 120.45 120.01 122.54 122.21 123.66 122.01

4. 122.33 124.73 127.55 120.45 120.45 122.07 122.34 123.51 122.55

5. 122.52 124.40 127.45 120.54 120.39 122.50 122.45 123.71 122.45

MEAN 122.45 124.53 127.14 120.53 120.09 122.34 122.14 123.44 122.12

S.D .0876 .1520 .3913 .0884 .5052 .2918 .5670 .4756 .3986

4.5. Microstructure

The microstructure of FA and SBR hybrid composite material was investigated by using

Scanning Electron Microscope (SEM). The SEM analysis shows that FA particles and SBR

particles are uniformly dispersed in to the matrix. By using SEM it can be analyzed that there

is any fracture or defect in the material or not. Figure 1-10 shows microstructure of different

FA reinforced composites material and FA and styrene butadiene hybrid composite material

at various magnification ranges.

Figure 18 shows the SEM analysis of the neat epoxy resin and hardener composite without

any reinforcing element.

Figure 19 shows the SEM of 1wt% FA reinforced composite at magnification × 5000. The

FA particles are uniformly dispersed and showing good interaction with the matrix material.

Figure 20 shows the SEM of 2wt% FA and 0.25 wt% rubber reinforced composite material at

magnification × 1000. From SEM analysis it is concluded that the FA particles are uniformly

dispersed in the matrix and as well as in the rubber phase. The spherical particles shown in

the figs are the FA particles generally called as the cenospheres.

Figure 21 shows the SEM of 3wt% FA and 0.25 wt% rubber reinforced composite material at

magnification × 1000. Fig shows the interaction of FA particles with the rubber phase in the

matrix material. The rubber phase and the FA particles can be easily seen in the composite by

SEM micrograph.

Figure 22 shows the SEM of 2wt% FA reinforced composite at magnification × 5000. Fig

shows that the FA particles are completely mixed with the matrix material.

Figure 23 shows the SEM of 3wt% FA reinforced composite at magnification × 10000. From

fig it can be shown that there is not so much good interaction of FA particles in the matrix.

Fig also shows the voids present in the composite.




Figure 24 shows the SEM of 2wt% FA and 0.5wt% rubber reinforced composite at

magnification × 5000. Fig shows the good interaction of FA particles with the rubber phase.

Figure 25 shows the SEM of fractured pin of 2wt% FA reinforced composite at magnification

× 1000. Fig shows that after fracture, FA particles sheared away from the matrix and leaving

very rough surface.

Figure 26 shows the SEM of 1wt% FA and 0.5wt% rubber reinforced composite at

magnification × 1000. From fig it can be revealed that the FA particles are uniformly

dispersed into the rubber phase.

Figure 27 shows the SEM of fractured pin of 2wt% FA and 0.5wt% rubber reinforced

composite rubber phase by fracture and leaving the voids into the matrix.




5. CONCLUSION

New composite materials have been developed by using FA and SBR and the key

observations were made as follows.

Addition of SBR lowers the density of the composite as compared to stand alone

ER,and also the addition of FA at lower percentages increases the density of




composite whereas at higher percentages decreases the density of the composite

material.

The tensile strength of the composite material decreases by increasing the FA content

in the matrix material.

The modulus of elasticity of the composite material increases by increasing the FA

content in the matrix material.

Wear rate of the hybrid composite material decreases by increasing the Fly ash

content in the matrix as compared to neat epoxy composites.

Addition of FA at lower percentages decreases the wear rate of composite where as at

higher percentages increases the wear rate of the composite material.

Increase of rubber concentration in fly ash composite results in increase in wear rate

of the hybrid composite.

SEM analysis was used to determine the micro structure of the hybrid composite

material and shows that the Fly ash and Rubber particles are uniformly distributed

over the matrix

Statistical analysis shows that Rockwell hardness of hybrid composite material

follows the normal distribution.

The hardness of the hybrid composite material increases by increasing the fly ash

content in the matrix material whereas the hardness of the composite material

decreases by increasing the rubber content in the matrix.

6. REFERENCES

[1] Prashanth T., Shekar K., Suryanarayan., Intl. Conf on Advanced Materials and

Composites ICAMC 2007, 24–27 October, CSIR, Trivandrum, India.

[2] H. V. Ramakrishna and S. K Rai, 2006, “Utilization of Granite Powder as a Filler for

Polybutylen Terepthalate Toughened ER”, Journal of Minerals & Materials

Characterization & Engineering, Vol. 5, No.1, pp 1-19.

[3] K.V. Mahandra, K. Radhakrishna, 2007, “Fabrication of Al–4.5% Cu alloy with FA

metal matrix composites and its characterization”. Materials Science-Poland, Vol. 25,

No. 1.

[4] Narongrit Sombatsompop, 2007, “Viscoelastic Properties of NBR filled with Lignite

FA”.




[5] Satapathy, Alok; Mishra, H K; Mishra, S S ;Mishra, S C; Thermal Spray Coatings Using

Industrial Waste and Ore Mineral,Bulletin of Orissa Physical Society, Volume 15,

February 2008, pp 129-134.

[6] WichianbutY., Charoenyut Dechwayukul, Lek Sikong, Wiriya Thongruang on

Mechanical Properties of Lignite Fly Ash/Natural Rubber Composites: Effects of Filter

Size, Loading and Silane Coupling Agent,Materials-2550, 10, (2005).

[7] Siddiqui, W. A., Ahmad, S., Tariq, M. I., Siddiqui, H. L. & Parvez, M. (2008). Acta

Cryst. C64, o4-o6.

[8] Rafat Siddique, William prince, Siham Kamali, Influence of Utilization of High-

Volumes of Class F Fly Ash on the Abrasion Resistance of Concrete, Leonardo

Electronic Journal of Practices and Technologies ISSN 1583-1078,10, (2007)

[9] JB Alam et al. (2006), Study of Utilization of Fly-Ash Generated from Barapukeria

Power Plant as Admixture in Manufacturing of Cement , Asian Journal of Civil

Engineering (Building and Housing) Vol. 7 No. 3.

http://dspace.nitrkl.ac.in/dspace/handle/2080/1418



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IJREAS Volume 2, Issue 5 (May 2012) ISSN: 2249-3905...

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