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Int. J. Mech. Eng. & Rob. Res. 2014 Sandesh Kamath et al., 2014

EXPERIMENTAL STUDY ON MECHANICALPROPERTIES OF RED GRANITE-EPOXY

PARTICULATE COMPOSITES

Sandesh Kamath1*, Joel D’Mello1 and S S Balakrishna1

*Corresponding Author: Sandesh Kamath, [email protected]

This paper presents a study on the red granite powder reinforced epoxy composite. Thecomposites have been fabricated by varying the granite-epoxy ratio on weight percentage basis.The compressive strength of the composite is studied by varying the epoxy content and thegrain size ratio by weight percentage using Taguchi’s orthogonal array L-27 and Analysis ofVariance (ANOVA) by assistance of Minitab 16 software. The damping behaviour is studiedusing experimental setup interfaced to LabVIEW software. The Mechanical properties areinvestigated by conducting tensile, flexural, impact, hardness and water absorption tests. Thecompression test results recorded a very good strength of 110 MPa for granite-epoxy ratio75:25 with grain size ratio 50:50. The composite shows high damping for granite-epoxy ratio80:20. The tensile, flexural and impact strengths are found to be maximum for granite-epoxyratio 50:50. Rockwell hardness test indicates highest hardness for granite-epoxy ratio 80:20.

Keywords: ANOVA, Compressive strength, Damping ratio, Epoxy, Red granite

INTRODUCTIONThe structural materials used in precisionmachines need to possess high strength aswell as good static and dynamic stiffness.Studies on the mechanical properties ofgranite-epoxy composites are reported in theliterature (Rama Krishna et al., 2005;Ramakrishna et al., 2005; Shetty RavindraRama and Rai, 2008; and Deepak et al.,2013). These composites have been reported

ISSN 2278 – 0149 www.ijmerr.comVol. 3, No. 4, October 2014

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Int. J. Mech. Eng. & Rob. Res. 2014

1 Department of Mechanical Engineering, Sahyadri College of Engineering & Management, Mangalore, Karnataka, India.

to be used as structural materials of precisionmachines due to its high strength, stiffness andmost importantly high vibration dampingcharacteristics (Selvakumar and Mohanram,2012). The materials specified for machinestructures must exhibit better modulus ofelasticity, yield strength, good mechanicalproperties such as high compressive, flexural,tensile strength, toughness and wearresistance (Antonio Piratelli-Filho and

Research Paper

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Flaminio Levy-Neto, 2010). The traditionalmaterials used for machine tool structures likecast iron and steel have high stiffness and goodmechanical properties, but at high speeds theytend to produce positional errors which mayaffect the accuracy and surface finish of themanufactured products (Antonio Piratelli Filhoand Flaminio Levy -Neto, 2010; andSelvakumar et al., 2012). Recent researchsuggests the use of composite materials forprecision machine structures. The studies ondamping of epoxy-granite composite arereported (Deepak et al., 2013; Antonio Piratelli-Filho and Flaminio Levy-Neto, 2010; SyathAbuthakeer et al., 2011; Selvakumar andMohanram, 2012; and Selvakumaret al., 2012).Damping of materials for machine structures isstudied using half power bandwidth method(Dai Gil Lee et al., 2004; Jung Do Suh and DaiGil Lee, 2008; Sung-Kyum Cho et al., 2011;Syath Abuthakeer et al., 2011; Niehues et al.,2012; and Selvakumar et al., 2012). RamaKrishna et al. (2005) carried out study onmechanical properties of granite-epoxycomposites. Antonio Piratelli-Filho and FlaminioLevy-Neto (2010) presented study concerningthe behaviour of particulate composite beamsbased on granite powder and epoxy and carriedout damping test. Antonio Piratelli-Filho andFrank Shimabukuro (2008) conductedcompression strength characterization ongranite-epoxy composites using design ofexperiments.

The present study on the red granite powderreinforced epoxy composites is an attempt tounderstand the static and dynamic behaviour.The composite is been developed with varyinggranite-epoxy ratio by weight percentageaccording to ASTM. A detailed study on the

compressive strength of composite is carriedout by varying the epoxy content and grain sizeratio by weight percentage using Analysis ofVariance and Taguchi’s orthogonal array(Philip Ross, 1996). The damping capacity ofthe composite is studied using experimentalsetup and LabVIEW software. The mechanicalproperties are studied by conducting tensile,f lexural, impact, hardness and waterabsorption tests by varying the granite-epoxyratio by weight percentage.

EXPERIMENTAL PROCEDUREMaterialsThe composite material is prepared byreinforcing red granite particles in epoxy resinLAPOX-12. The red granite slabs obtainedlocally are crushed and sieved. The resin usedis LAPOX-12 (3202) which is a liquid ofmedium viscosity along with hardener K-6.Hardener K-6 is a low-viscosity roomtemperature curing liquid. It gives a short potlife and rapid cure at normal ambienttemperature. The mixing ratio of resin tohardener is 10:1. The granite powder obtainedafter crushing is sieved using Sieving Machine.Different grain sizes are obtained from sievingprocess. The obtained granite grain sizeswere 53 µm to 74 µm, 75 µm to 105 µm, 106µm to 149 µm, 150 µm to 211 µm, 212 µm to299 µm, 300 µm to 424 µm meshes.

Sample PreparationTeflon moulds were prepared for the fabricationof composite specimens. The cavities forcompression, tension, bending, impact andhardness are engraved as per ASTM byvarious machining operations. The compositesamples were fabricated in the moulds atroom temperature by varying the granite-epoxy

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ratio by weight percentage. Small and largegrain sizes of red granite particulates weremixed in different proportions to improvecompactness and reduce porosity. Thespecimens were allowed to cure for 24 hoursin the mould at room temperature. Afterremoval from the mould the specimens werekept in electrically controlled oven at 60 ºC for4 hours to accelerate the curing process andthen left for 7 days at room temperature forcomplete curing.

Compression TestFor compression test ASTM D 695 is followed.The compression test was conducted on F.I.Emake universal testing machine of 40 kNcapacity, interfaced to FIE software to recordthe data. The influence of change in epoxycontent and grain size ratio of granite on thecompressive strength of composite isinvestigated using Taguchi’s orthogonal arrayand Analysis of Variance (ANOVA). Table 1shows the factors and the levels used for thestudy. Details of the grain size mix arehighlighted in Table 2. Taguchi’s orthogonalarray L-27 is used for two factors with threelevels and experiments are conducted. In each

case 3 specimens were fabricated, tested andthe results are reported.

Damping TestThe damping test is conducted usingexperimental setup interfaced to LabVIEWsoftware on fabricated beam type specimensof dimensions 200 mm x 20 mm x 20 mm. 50%of the grain sizes of 53 µm-74 µm, 75 µm-105µm, 106 µm-149 µm and 50% of 425 µm-599µm were used by weight to achievecompactness. The vibration response of thespecimens was obtained using impact testing,where an impact hammer was used to slightlyknock the specimen which is fixed on one endin cantilever manner. The resulting vibrationwas measured using a an accelerometer ofsensitivity 101.9 mv/g. The experimental setupconsisted of an impact hammer, anaccelerometer; signal conditioner, LabVIEWsoftware and data acquisition. The vibrationsignals are conditioned and displayed as afrequency spectrum through LabVIEWsoftware. The frequency spectrum is used toanalyze the fundamental frequencies and todetermine the damping ratio and logarithmicdecrement.

Flexural, Tensile, Impact,Hardness and Water AbsorptionTestsThe flexural, tensile, impact and hardness testsare carried out on granite-epoxy specimensprepared of ratio’s 50:50, 60:40, 70:30 and80:20 by weight percentage to investigate themechanical properties of the composite. Thegrain sizes 53 µm-74 µm, 75 µm-105 µm and106 µm-149 µm were used in equalproportions for the fabrication of composites.In each case 3 specimens were fabricated,tested and the results are reported.

Control Factors Level 1 Level 2 Level 3

Epoxy Content % 15 20 25

Grain Size Ratio % 50-50 60-40 70-30

Table 1: Control Factors and Levels Used

50-50 50% 50%

60-40 60% 40%

70-30 70% 30%

Table 2: Grain Size Mix for Different GrainSize Ratios

Grain Size Ratioby Weight

PercentageGrain Size:

75 µm-105 µmGrain Size:

300 µm-424 µm

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Flexural TestASTM D 790 is followed for flexural test. Thethree point bending test was conducted onInstron 3366 machine of capacity 10 KN, inwhich data was recorded with computerinterface. The strain rate of 1.5 mm/min wasset.

Tensile TestASTM D 638 is followed for tension test. Thetest was conducted on Instron 3366 machineof capacity 10 KN, in which data was recordedwith computer interface. The strain rate of 1.5mm/min was set.

Impact TestImpact strength was determined using the Izod-Charpy pendulum impact tester. The notchedspecimens according to ASTM E 23 wereprepared and Charpy test is conducted.

Hardness TestThe hardness of the composite was measuredusing Rockwell hardness testing machinereferring B-scale. The major and minor loadsapplied were 100 Kgf and 10 Kgf respectively.

Water Absorption TestThe composites were fabricated accordingto ASTM D 570-99. The compositespecimens were weighed before immersingin water. The specimens are immersed inwater for 15 days at room temperature tomeasure water absorption. Then specimenswere removed, cleaned with a cloth andweighed again. In each case 3 specimenswere fabricated. The percentage change inweight is determined as:

100%

WeightInitial

WeightInitialWeightFinalWeightinChange

RESULTS AND DISCUSSIONCompressive TestThe obtained compression test results areshown in Table 3.Taguchi method stresses onthe importance of studying the responsevariable using the signal-to-noise (S/N) ratio,resulting in minimization of qualitycharacteristic variation due to uncontrollableparameter. The compressive strength wasconsidered as the quality characteristic withthe concept of “the larger-the-better”. The S/Nratio is given by Equation (1).

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11log10/yn

NS ...(1)

where n is the number of measurements in atrial/row, in this case, n = 1 and y is themeasured value in a run/row. A higher S/N ratioindicates better performance of the response

Figure 1: Experimental Setupfor Damping Test

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variable. The high S/N ratio of 40.82 for 25%epoxy content with 50-50 grain ratio in Table 3indicates highest compressive strength.

Main effects plot for SN ratios shown inFigure 2a highlights that compressive strengthincreases with increase in epoxy content. Highcompressive strength is obtained for 25%epoxy content with 50-50 grain size ratio. Main

effects plot also shows that 50-50 grain sizeratio gives high compressive strengthcompared to grain size ratios 60-40 and 70-30. The interaction plot in Figure 2b shows that,grain size ratio 50-50 produces highcompressive strength for all epoxy content.There is a uniform mixture of fine and coarsegrains in 50-50 grain ratio which results in high

1. 15 50-50 77 37.72

2. 15 50-50 68 36.65

3. 15 50-50 71 37.02

4. 15 60-40 64 36.12

5. 15 60-40 59 35.41

6. 15 60-40 67 36.52

7. 15 70-30 49 33.80

8. 15 70-30 45 33.06

9. 15 70-30 46 33.25

10. 20 50-50 85 38.58

11. 20 50-50 87 38.79

12. 20 50-50 85 38.58

13. 20 60-40 77 37.72

14. 20 60-40 78 37.84

15. 20 60-40 81 38.16

16. 20 70-30 81 38.16

17. 20 70-30 68 36.65

18. 20 70-30 77 37.72

19. 25 50-50 101 40.08

20. 25 50-50 110 40.82

21. 25 50-50 98 39.82

22. 25 60-40 81 38.16

23. 25 60-40 88 38.88

24. 25 60-40 81 38.16

25. 25 70-30 95 39.55

26. 25 70-30 89 38.98

27. 25 70-30 92 39.27

Table 3. Compression Test Results

S. No. Epoxy Content byWeight Percentage

Granite Grain Size Ratioby Weight Percentage

Compressive Strengthin MPa Signal to Noise Ratio

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compressive strength and 25% epoxy contentprovides good wetting and bonding of graniteparticles.

Table 4 highlights the results of ANOVA forCompression Strength, in order to find the

significant factors which contribute tocompressive strength and their interactions.The P and F values report the significancelevel. P-value of 0.000 indicates that both epoxycontent and grain ratios are the significantfactors as compared to the interaction termwith P value of 0.001. The last column showsthe percentage contribution of each of theterms. It can be seen that epoxy content has acontribution of 69.56%, whereas grain ratiohas an influence of 17.53%, and the interactionhas contribution of 8.28%. Therefore epoxycontent is the most significant factor.

Damping TestThe magnitude versus frequency data isobtained from the damping test. The half-power bandwidth method is used to find outdamping ratio (), which is given by theequation

Source DOF Seq SS Adj SS Adj MS F P Percentage (%)

Epoxy Content 2 4700.22 4700.22 2350.11 135.58 0.000 69.56

Grain Ratio 2 1184.89 1184.89 592.44 34.18 0.000 17.53

Epoxy Content*Grain Ratio 4 559.56 559.56 139.89 8.07 0.001 8.28

Error 18 312.00 312.00 17.33 4.61

Total 26 6756.67 100

Note: DOF = Degrees of Freedom, Seq SS = Sequential Sum of Squares, Adj SS = Adjusted Sum of Squares, Adj MS = Adjusted MeanSquares, P = Percentage of Contribution.

Table 4. ANOVA for Compressive Strength

Figure 2: (a) Main Effects Plot for SNRatios, (b) Interaction Plot for SN Ratios

252015

41

40

39

38

37

36

35

34

33

EpoxyContent

SNra

tios

50-5060-4070-30

RatioGr ain

Interaction Plot for SN ratiosData Means

Signal-to-noise: Larger is better

252015

39

38

37

36

3570-3060-4050-50

Epoxy Content

Me

ano

fSN

rati

os

GrainRatio

Main Effects Plot for SN ratiosData Means

Signal-to-noise: Larger is better

85:15 0.02427 0.1525 200

80:20 0.0397 0.249 185

75:25 0.0171 0.10746 199

Pure Granite 0.0354 0.222 268

Neat Epoxy 0.03911 0.2459 114

Table 5: Damping Test Results

Granite-EpoxyRatio by Weight

Percentage

DampingRatio

LogarithmicDecrement

NaturalFrequency

Hz

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nfff

212 ...(2)

where is the damping ratio, fn represents thefundamental frequency and f = f2 – f1 is thebandwidth corresponding to half-power points.Logarithmic decrement () is found out byusing mathematical expression

21

2

...(3)

Table 5 shows the results of damping test.The red granite-epoxy ratio 80:20 showshighest damping ratio of 0.0397. The variationin damping with granite-epoxy ratio is shownin Figure 3.

Flexural TestThe variation in average ultimate flexuralstrength with granite-epoxy ratio is shown inFigure 4. The variation in flexural modulus withgranite-epoxy ratio is shown in Figure 5. Thethree point bending test shows high averagestrength of 50.43 MPa for granite-epoxy ratio50:50. The flexural strength decreases withincrease in granite particle content beyond50%. The flexural modulus increases withincrease in granite particle content andmaximum value of 13.57 GPa is obtained forratio 80:20. The decrease in ultimate bendingstrength may be due to improper wetting ofthe granite particles as the granite contentincreases.

Tensile TestThe variation in average ultimate tensilestrength with granite-epoxy ratio is shown inFigure 6. The variation in modulus ofelasticity with granite-epoxy ratio is shownin Figure 7. The high average tensilestrength of 28.22 MPa is observed forgranite-epoxy ratio 50:50. The tensilestrength decreases with increase in graniteparticle content beyond 50%. The modulus

Figure 3: Variation in Damping Ratiowith Granite-Epoxy Ratio

Figure 4: Variation in Flexural Strengthwith Granite-Epoxy Ratio

Figure 5: Variation in Flexural Moduluswith Granite-Epoxy Ratio

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of elasticity increases with the increase ingranite particle content and maximum valueof 6.04 GPa is obtained for ratio 80:20. Thedecrease in ultimate tensile strength may bedue to improper wetting of the graniteparticles at higher granite content.

Impact TestThe variation in impact strength with granite-epoxy ratio is shown in Figure 8.The highimpact strength of 50.33 kJ/m2 is obtainedfor granite-epoxy ratio 50:50. The impactstrength decreases with increase in graniteparticle content beyond 50%. The decrease

in strength at higher percentage of granitemay be due to improper wetting of graniteparticles.

Hardness TestThe hardness increases with increase ingranite particle content as shown in Figure 9.The high value of hardness of 78 RHN isobtained for granite-epoxy Ratio 80:20. Theincrease in hardness is due to the rigid graniteparticles.

Figure 6: Variation in Tensile Strengthwith Granite-Epoxy Ratio

Figure 7: Variation in Modulus of Elasticitywith Granite-Epoxy Ratio

Figure 8: Variation in Impact Strengthwith Granite-Epoxy Ratio

Figure 9: Variation in Hardness withGranite-Epoxy Ratio

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Water Absorption TestVariation in percentage change in weight withgranite-epoxy ratio is shown in Figure 10. Themaximum average change in weight of0.088% is obtained for ratio 50:50.

CONCLUSIONThe compressive strength is studied usingANOVA and found to be high for granite-epoxy ratio 75:25 with grain size ratio 50:50by weight percentage. It was noted that forall epoxy content, the grain size ratio 50:50shows high compressive strength. Theanalysis of variance shows that epoxycontent is the most significant factor whichcontributes to compressive strength. Thedamping test results show that thecomposite has high vibrations dampingcapacity and is a promising material forprecision machine tool structures. Theresults of mechanical tests on compositespecimens with granite-epoxy ratio 50:50 byweight percentage shows highest flexural,tensile and impact strength. The hardnesstest indicates highest result for granite-epoxyratio 80:20. The composite shows good

Figure 10: Variation in Percentage Changein Weight with Granite-Epoxy Ratio

resistance to water absorption and thechange in weight is negligible.

REFERENCES1. Antonio Piratelli-Filho and Frank

Shimabukuro (2008), “Characterization ofCompression Strength of Granite-EpoxyComposites Using Design ofExperiments”, Materials Research,Vol. 11, No. 4, pp. 399-404.

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3. Dai Gil Lee, Jung Do Suh, Hak Sung Kimand Jong Min Kim (2004), “Design andManufacture of Composite High SpeedMachine Tool Structures”, CompositesScience and Technology, Vol. 64,pp. 1523-1530.

4. Deepak D Ubale, Ajit P Patil and Kailas VGurav (2013), “Experimental Investigationof Material Properties of Epoxy Granite”,International Journal of Mechanical andProduction Engineering, Vol. 1, No. 3,ISSN: 2320-2092.

5. Jung Do Suh and Dai Gil Lee (2008),“Design and Manufacture of HybridPolymer Concrete Bed for High-SpeedCNC Milling Machine”, Springer ScienceBusiness Media, B.V., Vol. 4, pp. 113-121, DOI: 10.1007/s10999-007-9033-3.

6. Niehues K, Schwarz S and Zaeh M F(2012), “Reliable Material Damping RatioDetermination in Machine ToolStructures”, German Academic Societyfor Production Engineering (WGP),

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8. Rama Krishna H V, Padma Priya S, RaiS K and Varadarajulu A (2005), “Tensile,Impact, and Chemical ResistanceProperties of Granite Powder-EpoxyComposites”, Journal of ReinforcedPlastics and Composites, Vol. 24, p. 451.

9. Ramakrishna H V, Padma Priya S, Rai SK and Varadarajulu A (2005), “Studies onTensile and Flexural Properties of EpoxyToughened with PMMA/Granite Powderand Epoxy Toughened with PMMA/Fly AshComposites”, Journal of ReinforcedPlastics and Composites, Vol. 24, p. 1269.

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11. Selvakumar A, Ganesan K andMohanram P V (2012), “Dynamic Analysison Fabricated Mineral Cast Lathe Bed”,Journal of Engineering Manufacture.

12. Shetty Ravindra Rama and Rai S K(2008), “Tensile, Flexural, Density andVoid Content Studies on Granite PowderFilled Hydroxyl Terminated PolyurethaneToughened Epoxy Composites”, Journalof Reinforced Plastics and Composites,DOI: 10.1177/0731684408088891.

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