Research Article Properties of Graphene Oxide/Epoxy Resin Compositesdownloads.hindawi.com/journals/jnm/2014/696859.pdf · 2019-07-31 · e dynamic mechanical properties are conducted

Research ArticleProperties of Graphene OxideEpoxy Resin Composites

Jijun Tang Haijun Zhou Yunxia Liang Xinlan Shi Xin Yang and Jiaoxia Zhang

School of Materials Science and Engineering Jiangsu University of Science and Technology Zhenjiang 212003 China

Correspondence should be addressed to Haijun Zhou zhjjx163com and Jiaoxia Zhang myzjx0359163com

Received 19 July 2014 Accepted 14 September 2014 Published 6 November 2014

Academic Editor Xiao-Miao Feng

Copyright copy 2014 Jijun Tang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The graphene oxide (GO) was obtained by pressurized oxidation method using natural graphite as raw materials Then theGOepoxy resin composites were prepared by casting The mechanical and damping properties of composites were studied Asa result the impact intensity of GOepoxy resin composites was prominently improved with the content of the graphene oxideincreasing The glass transition temperature decreased and the damping capacity is improved

1 Introduction

In the narrow sense graphene refers to the single sheet ofgraphite just 0335 nm thick with the carbon atoms arrangedin a honeycomb lattice It can be seen as infinite aromaticmolecules sp2 hybridized carbonsrsquo bond length is only about142 A Broadly speaking graphite with less than 10 layerscan be called graphene Graphene is the basic structuralunit of carbon materials like carbon nanotubes graphitefullerene and so forth [1 2] It has become a research hotspotof materials science and coacervation physics in physicsresearch and practical application since it was discovered in2004 due to its excellent physical and chemical properties[3] But the interaction between pure graphene and othermedia is weak and there are strong van der Waals forcesbetween graphene sheets which make graphene prone toaggregate thus it is difficult to give full scope to its superiorperformance Graphene oxide has similar structure withgraphene hydroxyl and epoxy are located on the basal planeof graphene oxide carbonyl and carboxyl mainly in the edgeof the graphene oxide and these characteristics give grapheneoxide satisfactory composite capability and improve thedispersion of graphene oxide in the matrix resin [4 5] Epoxyresins are used in a variety of applications because of theirproperties such as thermal stability mechanical responselow density and electrical resistance but low tenacity anddestruction resistant ability restrict its use Liang et al [6]dispersed graphene in the epoxy resin to prepare the com-posite material The research shows that the electromagnetic

obstacle resistance effect of the prepared material signifi-cantly improved when the quality ratio of graphene andepoxy resin was 3 20 Bortz et al [7] prepared the compositematerials with functional graphene dispersed in the epoxyresin and the mechanical properties of the material aregreatly improved In the present work graphene oxide withgood compatibly was used to increase the toughness Theresult shows that graphene oxide can significantly improvethe toughness of epoxy resin matrix composites

2 Experimental Method

21 Materials Natural graphite (CP ignition residue le 015granularity le 30 120583m) was provided by Sinopharm ChemicalReagent Co Ltd

Hydrochloric acid (36ndash38) and concentrated sulfuricacid (98) were obtained from Xirsquoan San Pu Fine ChemicalPlant

Potassium permanganate (KMnO4 AR) and sodium ni-

trate (NaNO3 AR) were purchased from Shanghai Su Yi

Chemical Reagent Co LtdThe epoxy resin E-51 and curing agents were used for this

investigation The epoxy resin E-51 obtained fromWuxi BlueStar resin factory is the diglycidyl ether of bisphenol A resinwith an average epoxy value Ev = 051100 g Methyltetrahy-drophthalic anhydride (MeTHPA) as the curing agent wasproduced by Pu Yang Huicheng Electronic material Co Ltd

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 696859 5 pageshttpdxdoiorg1011552014696859

2 Journal of Nanomaterials

22 The Preparation of Graphene Oxide The graphene oxidewas obtained by pressurized oxidation [8] Put a certainamount of NaNO

3 natural graphite and concentrated sulfu-

ric acid (mass ratio is 1 1 50) into the hydrothermal reactoradd KMnO

4slowly under ice water and tighten the kettle

quickly Freeze for 2 h under 0∘C and place it in the ovenfor 25 h under 110∘C After it cools open the kettle pourit into deionized water mix it to dilute and add properamount of H

2O2 HCl to wash The water suspension is

centrifuged centrifuge 5min under 8000 rpm and discard thesupernatant Dialyze the underlayer deposition for three daysin the dialysis bag and then dry it in the oven under 80∘CUltrasonically disperse the dried solid for 30min in deionizedwater at a concentration of 2mgmL and make it becomeuniformly dispersed liquid which is namely graphene oxideaqueous solutionThe aqueous solution is dried the dispersedliquid in the oven under 80∘C grind to obtain the grapheneoxide

23 Preparation of GOEpoxy Resin Composites The graphe-ne oxide was added to the epoxy resin at 80∘C in order tolower the viscosity of the epoxy resin Filler (weight fractionsranging from 0wt to 1 wt) was dispersed in the epoxyresin and was sonicated for 30min After cooling to roomtemperature the hardener was added to the homogenousmixture and was compounded for another 10min Themixture was then taken into a preheated glass mold coatedwith the mold release agent The mold enclosed mixture wasdegassed at 80∘C under vacuum for 10min to remove bub-bles The mixture was cured at 80∘C1 h + 120∘C3 h +140∘C3 h to complete the crosslink reaction After beingcured completely the samples were incised according torelevant standard

24 Measurements and Characterizations The impact testswere performed at room temperature using an impact tester(XCJ-400) according to ASTM-D256 The sample size is80mm times 10mm times 4mm The flexural properties were mea-sured using a universal testingmachine under the three-pointloading scheme (ASTM-D790) The sample size is 80mm times15mm times 4mm Ten specimens of each composite were testedand themean values and standard deviations were computed

Dynamic mechanical analysis (DMA) was performedwith a DMAQ800 dynamic analyser at a heating rate of5∘Cminminus1 Samples were heated from 25∘C to 200∘C at a fixedfrequency of 1Hz

Scanning electron microscope (SEM) examinations wereobserved on the JMS-6480 instrument (Japanrsquos electronics)SEM at 50 kVThe specimens were coated with gold vapor tomake them conducting

3 Results and Discussion

Impact strength is the ratio of the energy absorbed and theoriginal cross-sectional area of the sample in the impactdamage process which can be used to evaluate impact resis-tance ofmaterial or judgematerialrsquos brittleness and toughnessand thus impact strength also known as impact toughness

00 02 04 06 0820

10

30

40

50

60

70

80

Impa

ct in

tens

ity (Jmiddotm

2)

GO content (wt)

Figure 1The effects of the graphene oxide with different content onthe impact strength of the epoxy resin composites

Figure 1 shows the effects of the graphene oxide with differentcontent on the impact strength of the epoxy resin compositesThe figure shows that while the impact strength of pureepoxy resin is 2866 kJm2 the content of graphene oxide is01 wt 02 wt 05 wt and 1 wt and the impact strengthof epoxy resin compositematerial is 5634 kJm2 6216 kJm27907 kJm2 and 5059 kJm2 that increase up to 97 117176 and 77 respectively which indicates that graphiteoxide can significantly improve the toughness of epoxy resinWith the increase of graphite content the impact strengthfirst increases and then decreases When the content ofgraphene oxide is 05 the improvement of the impactstrength is up to the best namely 176 Since there are lotsof oxygen-containing functional groups graphene oxide hasgood compatibility with epoxy resin and well dispersibilityin epoxy resin The large specific surface area of grapheneoxide and the high mechanical strength of the pleat onits surface greatly enhance the toughness of epoxy resincompositematerialThe impact strength increases with loweramplitude when the graphene oxide content is 1 wt whichprobably due to the dispersibility of graphene oxide in epoxyresin decreases with the increase of graphene oxide contentagglomeration and stress concentration appears thus theimpact strength decreases

The flexural modulus the ratio of bending stresses andthe deformation caused by bending refer to the ability ofantibending deformation of material in elastic limit Theflexural strength is the maximum stress a material can bearunder the specific deflection or the bending load when mate-rial breaks Figure 2 gives the effects of the graphene oxidewith different content on the flexural strength and flexuralmodulus of the epoxy resin composites As seen in thefigure the flexural modulus of pure epoxy resin is 3033MPaWhen the content of graphene oxide is 01 wt 02 wtthe flexural modulus has little difference with that of pureepoxy But while the content increases to 05 the flexuralmodulus is minimum which further prove that grapheneoxide improves the toughness of epoxy resin compositesThe bending strength of pure epoxy resin is 11433MPa

Journal of Nanomaterials 3

00 02 04 06 08 100

20

40

60

80

100

120

140

Bending intensity

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Bending modulus

Bend

ing

mod

ulus

(MPa

)

Bend

ing

inte

nsity

(MPa

)

GO content (wt)

Figure 2 The effects of the graphene oxide with different contenton the flexural strength and flexural modulus of the epoxy resincomposites

60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

E998400

(MPa

)

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO

Figure 3The relationship between the temperature and the storagemodulus of graphene oxideepoxy resin composite material

When graphene oxide content is 01 wt 02 wt 05 wtand 1 wt the bending strength of epoxy resin compositesis 106382MPa 101351MPa 11307MPa and 6025MPa anddecreases to 70 114 10 and 473 respectively Thisindicates that graphene oxide does not make the strength ofepoxy resin decrease significantly while increasing its tough-ness The toughness is best when the content of grapheneoxide is 01 wt but bending strength decreases only 10The toughness and rigidity of epoxy resin based compositeare worse than pure epoxy resin matrix when the content ofgraphene oxide is 1 wt due to uneven dispersion

The dynamic mechanical properties are conducted inorder to study the effect of graphene oxide content on therigidity and damping properties of epoxy resin based com-posite Figure 3 gives the relationship between the tempera-ture and the storage modulus of graphene oxideepoxy resincomposites It can be seen fromFigure 3 that low temperature

60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

Temperature (∘C)

E998400

(MPa

)

05wt GO

01wt GO

1wt GO

0wt GO

Figure 4 The relationship between the temperature and the lossmodulus of graphene oxideepoxy resin composites

zone corresponds to the glassy state of the polymer so thestorage modulus is very high at this region and decreasesslowly with the increase of the temperature when the polymerchain segments are frozen Deformation is mainly causedby the bending of the chemical bond in the polymer chainand the corresponding mechanical strengths reach the bestat the low temperature Free segments begin tomove with theincreases of the temperature and the excess energy dissipatesinto heat In a certain temperature range this change reachesthe maximum the storage modulus decreases rapidly andthis temperature range is the glass transition region Inthe transition zone mechanical strength significantly andrapidly decreases When the temperature is higher than thetransition point thematerial mainly shows the viscoelasticitybecause molecular chain can move freely therefore thestorage modulus representing rigidity and elasticity is nothigh Before reaching the glass transition temperature thereis slight decrease of storage modulus entirely with increase ofthe content of graphene oxide which confirms the decreaseof the bending strength mentioned above While the flexiblegraphene oxide improves the toughness of the composite therigidity decreases slightly at the same time due to the networkrelaxation Besides the glass transition temperature of thecomposites decreases because of the bad thermal stability ofgraphene oxide containing oxygen functional groups

The loss modulus on behalf of the viscidity of materialin the viscoelasticity reflects the energy consumption whichconvert to heat energy during the deformation ofmaterial [9]FromFigure 4 it can be known that before the glass transitiontemperature pure epoxy resin matrix mainly shows theelasticity of the material thus the loss modulus is small andchanges a little With temperature increasing free segmentsbegin to move and the excess energy dissipates into heat Thetransition reaches biggest in the glass transition temperaturezone and the loss factor curve appears the peak When thetemperature is higher than Tg the polymer is in the highelastic state segments can move and slide freely and theinternal friction and the loss modulus decrease After addingthe graphene oxide the loss modulus of the composites is


60 80 100 120 140 160

00

01

02

03

04

05

06

07

08

Tand

120575

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO

Figure 5 The relationship between the temperature and the lossfactor of graphene oxideepoxy resin composites

small relatively before reaching the glass transition temper-ature and increases slightly with increasing temperature Theloss modulus rises sharply and reaches the peak at the glasstransition temperature In addition since the addition ofgraphene oxidemakes themolecular chain network structurerelax the glass transition temperature moves to the lowertemperature region

Figure 5 shows the relationship between the temperatureof graphene oxideepoxy resin composite material and theloss factor The loss factor Tand 120575 is the ratio value of theloss modulus 11986410158401015840 and the storage modulus 1198641015840 Figure 5 showsthat the glass transition temperature of pure epoxy resincorresponding to the loss factor peak value is 140∘C andloss factor is 065 The glass transition temperature movesto the lower temperature zone and the loss factor increaseswith the addition of graphene oxide When the content ofgraphene oxide is 05 the loss factor Tand 120575 reaches thebiggest namely 072 and the glass transition temperature isthe lowest This indicates that while increasing the toughnessof epoxy resin graphene oxide could transform the appliedmechanical energy into other forms of energy promptly andthus improve the damping property of epoxy resinWhen thecontent is 1 wt the damping performance get bad and themechanical properties decrease which probably causes by thepoor dispersion of graphene oxide

Figure 6 is the impact fracture morphology of the GOepoxy resin composites Figure 6(a) shows the typical brittlefracture of pure epoxy resin whose section is neat andthe crack appears smooth river pattern zones while inFigure 6(b) the impact sections of GOepoxy resin com-posites are irregular in size and there are more failuresurfaces The epoxy groups of graphene oxide make split-phase graphene oxide and the matrix have excellent inter-face compatibility When the system loaded homogeneouslydispersed graphene oxide in the composites could initiateand terminate cracks under the stress The system consumeslots of energy In the morphology of fracture impact andcleavage fracture surfaces are rough the failure surfaces aremore energy consumption is larger and the appearance of

(a)

(b)

Figure 6The SEM images of the surface appearance of the abrasionof (a) pure epoxy resin composites and (b) GOepoxy resin compos-ites

ductile failure indicates the achievement of the purpose oftoughening

4 Conclusion

The graphene oxide was obtained by pressurized oxidationmethod and the polymerization GOepoxy resin compositeswere successfully prepared by casting Graphene oxide sig-nificantly enhances the toughness of the composites while itdoes not decrease the strength of the composites obviously Asthe graphene oxide content is 05 wt the impact intensity ofthe composites reaches the largest value by 176 comparedwith pure epoxy resin matrix and the damping capacity isobviously improved

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper


Acknowledgments

The authors greatly acknowledge the Special Fund forBasic Scientific Research of Central College JiangsuProvincial Cooperative Innovation Fund of China (Grantno BY2012178) and National Natural Science Foundation(51402132)

References

[1] K S Novoselov A K Geim S V Morozov et al ldquoElectric fieldin atomically thin carbon filmsrdquo Science vol 306 no 5696 pp666ndash669 2004

[2] M Hirata T Gotou S Horiuchi M Fujiwara and M OhbaldquoThin-filmparticles of graphite oxide 1 high-yield synthesis andflexibility of the particlesrdquoCarbon vol 42 no 14 pp 2929ndash29372004

[3] Q-H Yang W Lu Y-G Yang and M-Z Wang ldquoFree two-dimensional carbon crystal-single-layer graphenerdquoXinxing TanCailiao New Carbon Materials vol 23 no 2 pp 97ndash103 2008

[4] S Stankovich D A Dikin R D Piner et al ldquoSynthesis of gra-phene-based nanosheets via chemical reduction of exfoliatedgraphite oxiderdquo Carbon vol 45 no 7 pp 1558ndash1565 2007

[5] R van Noorden ldquoMoving towards a graphene worldrdquo Naturevol 442 no 7100 pp 228ndash229 2006

[6] J Liang YWang Y Huang et al ldquoElectromagnetic interferenceshielding of grapheneepoxy compositesrdquo Carbon vol 47 no 3pp 922ndash925 2009

[7] D R Bortz E G Heras and I Martin-Gullon ldquoImpressive fa-tigue life and fracture toughness improvements in grapheneoxideepoxy compositesrdquo Macromolecules vol 45 no 1 pp238ndash245 2012

[8] C Bao L Song W Xing et al ldquoPreparation of graphene bypressurized oxidation and multiplex reduction and its polymernanocomposites by masterbatch-based melt blendingrdquo Journalof Materials Chemistry vol 22 no 13 pp 6088ndash6096 2012

[9] Y-P Zheng J-X Zhang Y-H Xu F Dai and B Wang ldquoMois-ture absorption mechanism of epoxy resin matrices throughpositron annihilation techniquerdquo Polymeric Materials Scienceand Engineering vol 25 no 8 pp 110ndash113 2009

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Advances in

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Nano

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Journal ofNanomaterials


22 The Preparation of Graphene Oxide The graphene oxidewas obtained by pressurized oxidation [8] Put a certainamount of NaNO

3 natural graphite and concentrated sulfu-

ric acid (mass ratio is 1 1 50) into the hydrothermal reactoradd KMnO

4slowly under ice water and tighten the kettle

quickly Freeze for 2 h under 0∘C and place it in the ovenfor 25 h under 110∘C After it cools open the kettle pourit into deionized water mix it to dilute and add properamount of H

2O2 HCl to wash The water suspension is

centrifuged centrifuge 5min under 8000 rpm and discard thesupernatant Dialyze the underlayer deposition for three daysin the dialysis bag and then dry it in the oven under 80∘CUltrasonically disperse the dried solid for 30min in deionizedwater at a concentration of 2mgmL and make it becomeuniformly dispersed liquid which is namely graphene oxideaqueous solutionThe aqueous solution is dried the dispersedliquid in the oven under 80∘C grind to obtain the grapheneoxide

23 Preparation of GOEpoxy Resin Composites The graphe-ne oxide was added to the epoxy resin at 80∘C in order tolower the viscosity of the epoxy resin Filler (weight fractionsranging from 0wt to 1 wt) was dispersed in the epoxyresin and was sonicated for 30min After cooling to roomtemperature the hardener was added to the homogenousmixture and was compounded for another 10min Themixture was then taken into a preheated glass mold coatedwith the mold release agent The mold enclosed mixture wasdegassed at 80∘C under vacuum for 10min to remove bub-bles The mixture was cured at 80∘C1 h + 120∘C3 h +140∘C3 h to complete the crosslink reaction After beingcured completely the samples were incised according torelevant standard

24 Measurements and Characterizations The impact testswere performed at room temperature using an impact tester(XCJ-400) according to ASTM-D256 The sample size is80mm times 10mm times 4mm The flexural properties were mea-sured using a universal testingmachine under the three-pointloading scheme (ASTM-D790) The sample size is 80mm times15mm times 4mm Ten specimens of each composite were testedand themean values and standard deviations were computed

Dynamic mechanical analysis (DMA) was performedwith a DMAQ800 dynamic analyser at a heating rate of5∘Cminminus1 Samples were heated from 25∘C to 200∘C at a fixedfrequency of 1Hz

Scanning electron microscope (SEM) examinations wereobserved on the JMS-6480 instrument (Japanrsquos electronics)SEM at 50 kVThe specimens were coated with gold vapor tomake them conducting

3 Results and Discussion

Impact strength is the ratio of the energy absorbed and theoriginal cross-sectional area of the sample in the impactdamage process which can be used to evaluate impact resis-tance ofmaterial or judgematerialrsquos brittleness and toughnessand thus impact strength also known as impact toughness

00 02 04 06 0820

10

30

40

50

60

70

80

Impa

ct in

tens

ity (Jmiddotm

2)

GO content (wt)

Figure 1The effects of the graphene oxide with different content onthe impact strength of the epoxy resin composites

Figure 1 shows the effects of the graphene oxide with differentcontent on the impact strength of the epoxy resin compositesThe figure shows that while the impact strength of pureepoxy resin is 2866 kJm2 the content of graphene oxide is01 wt 02 wt 05 wt and 1 wt and the impact strengthof epoxy resin compositematerial is 5634 kJm2 6216 kJm27907 kJm2 and 5059 kJm2 that increase up to 97 117176 and 77 respectively which indicates that graphiteoxide can significantly improve the toughness of epoxy resinWith the increase of graphite content the impact strengthfirst increases and then decreases When the content ofgraphene oxide is 05 the improvement of the impactstrength is up to the best namely 176 Since there are lotsof oxygen-containing functional groups graphene oxide hasgood compatibility with epoxy resin and well dispersibilityin epoxy resin The large specific surface area of grapheneoxide and the high mechanical strength of the pleat onits surface greatly enhance the toughness of epoxy resincompositematerialThe impact strength increases with loweramplitude when the graphene oxide content is 1 wt whichprobably due to the dispersibility of graphene oxide in epoxyresin decreases with the increase of graphene oxide contentagglomeration and stress concentration appears thus theimpact strength decreases

The flexural modulus the ratio of bending stresses andthe deformation caused by bending refer to the ability ofantibending deformation of material in elastic limit Theflexural strength is the maximum stress a material can bearunder the specific deflection or the bending load when mate-rial breaks Figure 2 gives the effects of the graphene oxidewith different content on the flexural strength and flexuralmodulus of the epoxy resin composites As seen in thefigure the flexural modulus of pure epoxy resin is 3033MPaWhen the content of graphene oxide is 01 wt 02 wtthe flexural modulus has little difference with that of pureepoxy But while the content increases to 05 the flexuralmodulus is minimum which further prove that grapheneoxide improves the toughness of epoxy resin compositesThe bending strength of pure epoxy resin is 11433MPa


00 02 04 06 08 100

20

40

60

80

100

120

140

Bending intensity

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Bending modulus

Bend

ing

mod

ulus

(MPa

)

Bend

ing

inte

nsity

(MPa

)

GO content (wt)


60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

E998400

(MPa

)

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO




60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

Temperature (∘C)

E998400

(MPa

)

05wt GO

01wt GO

1wt GO

0wt GO





60 80 100 120 140 160

00

01

02

03

04

05

06

07

08

Tand

120575

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO





(a)

(b)



4 Conclusion





Acknowledgments


References

















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




00 02 04 06 08 100

20

40

60

80

100

120

140

Bending intensity

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Bending modulus

Bend

ing

mod

ulus

(MPa

)

Bend

ing

inte

nsity

(MPa

)

GO content (wt)


60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

E998400

(MPa

)

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO




60 80 100 120 140 160

0

500

1000

1500

2000

2500

3000

3500

Temperature (∘C)

E998400

(MPa

)

05wt GO

01wt GO

1wt GO

0wt GO





60 80 100 120 140 160

00

01

02

03

04

05

06

07

08

Tand

120575

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO





(a)

(b)



4 Conclusion





Acknowledgments


References

















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




60 80 100 120 140 160

00

01

02

03

04

05

06

07

08

Tand

120575

Temperature (∘C)

05wt GO

01wt GO

1wt GO0wt GO





(a)

(b)



4 Conclusion





Acknowledgments


References

















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Acknowledgments


References

















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Properties of Graphene Oxide/Epoxy Resin Compositesdownloads.hindawi.com/journals/jnm/2014/696859.pdf · 2019-07-31 · e dynamic mechanical properties are conducted

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