SPECIAL ISSUE - ORIGINAL ARTICLE

Experimental analysis on tensile properties of FRPwith nano clay

S. Sundaram & R. Nagalingam & R. Satheesh Raja

Received: 5 February 2008 /Accepted: 17 September 2008# Springer-Verlag London Limited 2008

Abstract The field of fiber-reinforced plastic (FRP) nano-composites is stimulating both fundamental and appliedresearch because these nanoscale materials often exhibitmechanical, physical, and chemical properties that aredramatically different from conventional microcomposites.A large number of nanoparticles, layered fibers, andpolymeric whiskers are being used for the preparation ofnanocomposites. Since the Toyota research group’s pioneer-ing work on nylon 6/layered silicate nanocomposites,polymer nanocomposites containing layered silicates haveattracted much attention. These nanocomposites can exhibitincreased modulus, decreased thermal expansion coefficient,increased solvent resistance, and enhanced ionic conductivityas compared to the polymer alone. Here, we have preparedFRP with nanocomposites in the combination of polyesterresin, E-glass fiber, and nano-montmorillonite (nano clay).The mechanical properties of the nanocomposites werestudied. It results in increase of tensile strength, percentelongation and yield strength, moderate increase in Poissonratio, and reduced area.

Keywords Nanocomposites . Montmorillonite . FRP

1 Introduction

The dreams beyond human imagination have almostbecome a reality and the unreachable is reached. We areentering into the gateway of next generation “nanotechage”, where smaller and shorter things will play a big role.In this, nanotechnology is a hybrid science combiningengineering, information technology, chemistry, and biolo-gy. The goal of nanotechnology is to manipulate atomsindividually at nanoscale dimensions and processing ofseparation, consolidation, and deformation of materials byone atom or one molecule which includes many techniquesused to create structures at a size scale below 100 nm.Nanotechnology is the design, characterization, production,and application of structures, devices, and systems bycontrolling shape and size at the nanoscale. One nanometeris eight to ten atoms span. The human hair is approximately70,000 to 80,000 nm thick. Nanotechnology has been put topractical use for a wide range of applications, includingstain-resistant paints. There is no single field of nanotech-nology. “Nanotechnology is the understanding and controlof matter at dimensions of roughly 1 to 100 nm, whereunique phenomena enable novel applications”. The dreamof a near perfect future will come true with these smartmaterials. Nanotechnology is all set to prove that there areno limits for technological developments and it is going tomake our life easier than before. Though nanotechnology isat its infant stage, the lead time for it maturing intotechnology can be expected in the next 10–15 years. Thescope range and potential applications of this technologycould not be defined. Nanotechnology will find itsapplication in energy, medicine, electronics, computing,security and material sciences, etc.

Int J Adv Manuf TechnolDOI 10.1007/s00170-008-1868-8

S. SundaramDepartment of Manufacturing Engineering, Annamalai University,Annamalai Nagar, Tamil Nadu 608 002, India

R. Nagalingam (*) :R. Satheesh RajaDepartment of Mechanical Engineering,Jayamatha Engineering College,Kanyakumari Dist, Tamil Nadu 629 301, Indiae-mail: nagu_7835@rediffmail.com

“Building things, atom by atom, molecule by molecule”is nanotechnology. Put differently, it is a ‘bottom-up’manufacturing approach in which machines and mecha-nisms are built with nanoscale dimensions to build thingson small scales. In this, one has to manipulate atomsindividually but the real challenge is to place the atomsprecisely where we wish on a structure.

2 Literature review

Blending molten polymer and inorganic clays can resultin a class of new materials, in which nanoscale clayparticles, generally layered silicates, are molecularlydispersed within the polymeric matrix. Such polymer–clay nanocomposites exhibit dramatic increase in severalproperties, including mechanical strength, heat resistance,and a decrease in gas permeability when compared to thepolymeric matrix alone. The montmorillonite inorganicclay consists of stacked silicate sheets, each approxi-mately 200 nm long and 1 nm thick. The spacingbetween each sheet (gallery) is also of the order of 1 nmand this quantity is clearly smaller than the averageradius of gyration of any conventional polymer. There-fore, entropy generally constitutes a large barrier thatprevents the polymer from penetrating these galleries andbecoming an intercalated material. Then, determine thefactors that control the macroscopic phase behavior ofthe mixture. Finally, the properties of the polymer–claynanocomposites commonly depend on the structure ofthe material [1]. Nanoparticles are presently considered tobe high-potential filler materials for the improvement ofmechanical and physical polymer properties. The nano-metric size leading to huge specific surface areas of up tomore than 1,000 m2/g and their unique properties (of atleast some of these nanoparticles) have caused intensiveresearch activities in the fields of natural and engineering

sciences. Candidates in the collectivity of nanoparticleswith a high potential for the enhancement of mechanicaland physical properties of polymers are carbon nanotubes[2–4]. Their mechanical properties [5–8], a high aspectratio, high Young’s modulus, and tensile strength, incombination with an electrical and thermal conductivitymake them interesting materials for use as nanofillers inpolymers and open up new perspectives for multi-functional materials, e.g., conductive polymers withimproved mechanical performance. A nano-modificationof the epoxy matrix leads to novel fiber-reinforced plastics(FRPs) with enhanced matrix-dominated mechanicalproperties and an anisotropic electrical conductivity. Inorder to efficiently exploit the potential of nanoparticles,an appropriate dispersion and sufficient amounts of nano-modified epoxy are required. Both requirements can befulfilled by the application of the introduced calanderingmethod to manufacture the nanotube/epoxy suspension.The nanocomposites, reinforced with carbon nanotubes,exhibit an improved mechanical performance. Especiallyan influence of the CNTs on the fracture toughness couldbe observed [9]. Synthesis and characterization of inorganic–organic hybrid materials have received more and moreconsiderable attention. Inorganic–organic hybrid materialscan combine remarkable properties of inorganic phase andorganic polymer. Epoxy resins are widely used in a large scaleas packaging materials, laminates, and adhesives in the fieldof electric and electronic industries owing to an exceptionalcombination of properties such as toughness, adhesion, andchemical resistance. However, waterproof, thermal, andmechanical properties are not sufficient to meet the require-ment of advanced electronics.Many efforts have beenmade toimprove properties of epoxy resins. They had been modified

Table 1 Combination of specimens

Specimen Combinations Proportion % Weight (g)

A PR 75 1,125FR 25 375

B PR 70 1,050FR 30 450

C PR 70 1,050FR 25 375NP 5 75

D PR 70 1,050FR 20 300NP 10 150

PR polyester resin, FR fiber, NP nanopowder

0

10

20

30

40

50

60

70

80

90

100

A B C DSpecimens

UT

S

Fig. 1 UTS for various specimens

Int J Adv Manuf Technol

with carboxyl-terminated acrylonitrile-buta-diene, amine-terminated butadiene acrylonitrile, functionally terminatedacrylates, poly (phenylene oxide), and alkylene oxides toimprove their mechanical properties and with silicone toimprove thermal properties. Nano-TiO2, nano-ZnO, andnano-SiO2 were dispersed in epoxy resin to improve bothmechanical and thermal properties for their large specificsurface area. Modification of nano-SiO2 in epoxy resin-basedcomposite was more effective than that of standard SiO2 fortensile properties and impact properties due to large specificsurface area and active groups on surfaces of nano-SiO2

particles. Similar behavior has been shown for the toughness

of epoxy resin-based composite with nano-SiO2 and standardSiO2 in SEM images [10].

3 Preparation of material

Prepare molding box with the required size and use waxpolish and polyvinyl alcohol which acts as a releasingagent. Apply the mixture of nanopowder and polyesterresin over the emulsion fiber mat of 300 μm thickness.

0

2

4

6

8

10

12

14

A B C DSpecimens

% E

long

atio

n

Fig. 2 Elongation for various specimens

0

1

2

3

4

5

6

7

8

A B C DSpecimens

Yie

ld S

tren

gth

Fig. 3 Yield strength for various specimens

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

A B C DSpecimens

Pois

son

Rat

io

Fig. 4 Poisson ratio for various specimens

0

1

2

3

4

5

6

7

A B C DSpecimens

% R

educ

tion

in A

rea

Fig. 5 Percent reduction in area for various specimens

Int J Adv Manuf Technol

4 Test procedure

Tensile tests measure the force required to break a specimenand the extent to which the specimen stretches or elongatesto that breaking point. Tensile tests produce a stress–displacement diagram and load–displacement diagram,which is used to determine tensile modulus. The data isoften used to specify a material, to design parts to withstandapplication force, and as a quality control check of materials.ASTM D 638 specimens are placed in the grips of theuniversal testingmachine (UTM) at a specified grip separationand pulled until failed at test speed of 50 mm/min formeasuring strength and elongation.

5 Results and discussions

Table 1 shows various combinations of polyester resin,fiber, and nanopowder (montmorillonite) in wt.%. Speci-mens A and B were prepared in the combination of PR andFR only. Specimens C and D were prepared by optimizingthe PR and changing the wt.% of fiber and nanopowder.These molded specimens were prepared as per ASTM D638 and tested in computerized UTM in 50 mm/min atroom temperature.

Figure 1 illustrates the plots of ultimate tensile strength(UTS) in N/mm2 versus specimens of various combinations.It can be seen that specimen A yielded 63 N/mm2 for 5 wt.%increment of FR and B yielded UTS in 57 N/mm2 inaddition of 5 wt.% of FR, reducing almost 10% of UTS forthe increment of 5% in fiber due to improper bondingstrength between FR and PR. Specimen C yielded 95 N/mm2

for the 5 wt.% increment of NP. Almost 50% UTS increaseddue to better bonding strength between FR, PR, and NP.Specimen D yielded 53 N/mm2 for the 10 wt.% increment ofNP; it can reduce 50% of UTS.

Figure 2 illustrates the plots of % elongation versusspecimens of various combinations. It can be seen thatspecimen A elongated 8.6%, B elongated 7.6% (addition of5 wt.% of fiber), C elongated 9.1% (addition of 5 wt.% ofNP), and D elongate 12.5% (addition of 10 wt.% of NP).The increment of 5 wt.% of FR reduced the elongation 1%.Increment of 5% of NP increased the elongation 0.5% and10 wt.% of increment of NP gives 3.9% increment ofelongation.

Figure 3 illustrates the plots of yield strength in N/mm2

versus different specimens. For 5 wt.% increment of FR,specimen A yielded 7.142 N/mm2 and B yielded7.045 N/mm2. For the addition of 5 wt.% of NP, specimen Cyielded 7.245 N/mm2 and specimen D yielded 5.227 N/mm2.It shows that addition of NP will slightly increase the yield

strength. When NP is added in this FRP polymer, it canincrease the plasticity of the material.

Figure 4 illustrates the plots of Poisson ratio versusdifferent specimens. By addition of 5 wt.% of FR, specimenA has 0.058 Poisson ratio and in specimen B, the Poissonratio is increased to 0.171. Addition of 5 wt.% of NP inspecimen C can increase the Poisson ratio to 0.110 and inspecimen D to 0.088. This result shows a moderate value ofPoisson ratio for specimen C.

Figure 5 illustrates the plots of % reduction in areaversus different specimens. It can be seen that, for 5 wt.%increment of FR, specimen A reduces 1.258% reduction inarea and B reduces 5.92%. For the addition of 5 wt.% ofNP, specimen C reduced 3.115%. For the addition of 10 wt.% of NP, specimen D reduced 3.18%. Specimen C has alow reduction in area due to the addition of 5 wt.% of NP.Addition of 5 wt.% of NP gives a lesser value of reductionin area due to the proper bonding between nanopowder andpolymer. Specimen A has the lowest reduction in area dueto more quantity of polyester resin.

6 Conclusion

In this study, the tensile behavior of an experimentallyproduced nano-FRP in various combinations was investi-gated at room temperature in 0.833 strain rates. The resultsare summarized as follows. The nano-FRP has sufficientlyhigh ultimate tensile strength and 50% improvement ofUTS at 5 wt.% increment of nanopowder. Elongationincreases with the addition of nanopowder 0.5 wt.%;improvement in elongation was observed with the additionof 5% NP. Moreover, 3.9% improvement in elongation wasobserved with the addition of 10% NP. Yield strengthincreases into 7.24 N/mm2 with the addition of 5% NP.Poisson ratio moderately increases with an addition ofnanopowder wt.%. A 50% improvement in Poisson ratiowas observed at 5 wt.% increment of nanopowder.Reduction in area greatly reduced to 3.115 with the additionof 5% NP. The five parameters of this study which canpredict the influences of nanoparticle in FRP are greatlyincreasing UTS, % elongation and yield strength, moderateincrease in Poisson ratio, and reduction in area.

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