Strength Characterization of E-glass Fiber Reinforced Epoxy Composites with Filler Materials

doi:10.4236/jmmce.2013.16054

Paper Menu >>

Journal Menu >>

Journal of Minerals and Materials Characterization and Engineering, 2013, 1, 353-357

Published Online November 2013 (http://www.scirp.org/journal/jmmce)

http://dx.doi.org/10.4236/jmmce.2013.16054

Open Access JMMCE

Strength Characterization of E-glass Fiber Reinforced

Epoxy Composites with Filler Materials

K. Devendra1, T. Rangaswamy2

1Department of Mechanical Engineering, SKSVMACET, Laxmeshwar, India

2Department of Mechanical Engineering, Government Engineering College (GEC), Hassan, India

Email: [email protected]

Received September 2, 2013; revised October 17, 2013; accepted October 28, 2013

License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

In this research work, an investigation was made on the mechanical properties of E-glass fiber reinforced epoxy com-

posites filled by various filler materials. Composites filled with varying concentrations of fly ash, aluminum oxide

(Al2O3), magnesium hydroxide (Mg(OH)2) and hematite powder were fabricated by standard method and the mechani-

cal properties such as ultimate tensile strength, impact strength and hardness of the fabricated composites were studied.

The test results show that composites filled by 10% volume Mg(OH)2 exhibited maximum ultimate tensile strength and

hardness. Fly ash filled composites exhibited maximum impact strength.

Keywords: Composites; Fillers; Mechanical; Properties; Strength

1. Introduction

Polymers have replaced many of the conventional met-

als/materials in various applications. This is possible be-

cause of the advantages such as ease of processing, pro-

ductivity, cost reduction, etc. offered by polymers over

conventional materials. In most of these applications, the

properties of polymers are modified by using fibers to

suit the high strength/high modulus requirements. The

high performance of continuous fiber (e.g. carbon fiber,

glass fiber) reinforced polymer matrix composites is well

known and documented [1]. Among the thermosetting

polymers, epoxy resins are the most widely used for

high-performance applications, such as matrices for fiber

reinforced composites, coatings, structural adhesives and

other engineering applications. Epoxy resins are charac-

terized by excellent mechanical and thermal properties,

high chemical and corrosion resistance, low shrinkage on

curing and the ability to be processed under a variety of

conditions [2]. However, these composites have some

disadvantages related to the matrix dominated properties

which often limit their wide applications. In the industry,

the addition of filler materials to a polymer is a common

practice. This improves not only stiffness, toughness,

hardness, heat distortion temperature, and mold shrink-

age, but also reduces the processing cost significantly. In

fact, more than 50% of all produced polymers are in one

way or another filled with inorganic fillers to achieve the

desired properties [3]. Mechanical properties of fiber-

reinforced composites are depending on the properties of

the constituent materials (type, quantity, fiber distribu-

tion and orientation, void content). Beside those proper-

ties, the nature of the interfacial bonds and the mecha-

nisms of load transfer at the interphase also play an im-

portant role [4]. Nowadays specific fillers/additives are

added to enhance and modify the quality of composites

as these are found to play a major role in determining the

physical properties and mechanical behavior of the com-

posites. For many industrial applications of glass fiber re-

inforced epoxy composite, information about their me-

chanical behavior is of great importance. Therefore, in

this work, the mechanical behavior of E-glass fiber rein-

forced epoxy composites filled by varying concentration

of fly ash Al2O3, Mg (OH)2 and hematite powder has

been studied.

2. Experimentation

2.1. Materials for Composites

ARALDITE (L-12) epoxy had been used as matrix mate-

rial for reinforced composites in this experimental work.

For reinforcing epoxy matrix, E-glass fiber was used

along with hardener K-6. Fly ash, Al2O3, Mg(OH)2 and

hematite powder was used as filler materials. Fly ash was

K. DEVENDRA, T. RANGASWAMY

354

obtained from thermal power plant. Measured density of

fly ash particles was 2.0 g/cc. These micron-sized ele-

ments are consists primarily of silica (59.5%), alumina

(20.3%), Fe2O3 (6.5%), titanium (1.28%), potassium ox-

ide (0.96%), MgO (0.50%), Phosphates (0.05%), Sulfates

(0.345%) and unburned coal [5]. Most of these particles

have a gas bubble at the center. Aluminum oxide parti-

cles is a ceramic powder commonly used filler, it is also

used as an abrasive due to its hardness. Magnesium hy-

droxide is an inorganic compound and it is a white pow-

der with specific gravity of 2.36, very slightly soluble in

water; decomposing at 350˚C. Magnesium hydroxide is

attracting attention because of its performance, price, low

corrosiveness and low toxicity. Hematite is an iron oxide

with the same crystal structure as that of corundum (ru-

bies and sapphires). Usually the color varies between a

metallic grey and red. Hematite is one of the oldest

stones mined in our history.

2.2. Fabrication of Composites

The E-glass/Epoxy based composite slabs filled with

varying concentrations of (0%, 10% and 15% volume)

fly ash, aluminum oxide (Al2O3), magnesium hydroxide

(Mg(OH)2), and hematite powder were prepared. The

volume fraction of fiber, epoxy and filler materials were

determined by considering the density, specific gravity

and mass. Fabrication of the composites is done at room

temperature by hand lay-up techniques. The required

ingredients of resin, hardener, and fillers are mixed thor-

oughly in a basin and the mixture is subsequently stirred

constantly. The glass fiber positioned manually in the

open mold. Mixture so made is brushed uniformly, over

the glass plies. Entrapped air is removed manually with

squeezes or rollers to complete the laminates structure

and the composite is cured at room temperature.

2.3. Specimen Preparation

The prepared E-glass fiber reinforced epoxy composite

slabs filled by various filler materials were taken out

from the mold and then specimens of suitable dimensions

were prepared from the composite slabs for different

mechanical tests according to ASTM standards. The test

specimens were cut by slabs by using diamond tipped

cutter and different tools in the work shop. Three identi-

cal test specimens were prepared for different test. Des-

ignation and composition of prepared composite slabs are

presented in Table 1.

3. Mechanical Property Testing

Mechanical properties of composites were evaluated by

tensile, impact and hardness measurements. Tensile, im-

pact and hardness tests were carried out using Universal

testing machine, impact machine and hardness testing

Table 1. Designation and compositions of fabricated com-

posites.

Material

Designation

Glass Fiber

(Volume %)

Epoxy

(Volume %)

Filler Materials

(Volume %)

GE 50 50 Nil

GEF1 50 40 10% Fly ash

GEF2 50 35 15% Fly ash

GEA1 50 40 10% Al2O3

GEA2 50 35 15% Al2O3

GEM1 50 40 10% Mg(OH)2

GEM2 50 35 15% Mg(OH)2

GEH1 50 40 10% Hematite Powder

GEH2 50 35 15% Hematite Powder

machine respectively. Three identical samples were test-

ed for tensile strength, impact strength and hardness.

3.1. Ultimate Tensile Strength

Tensile tests were examined according to ASTM D3039

using a universal testing machine at room temperature.

Test specimens having dimension of length 250 mm,

width of 25 mm and thickness of 2.5 mm. The specimen

was loaded between two manually adjustable grips of a

60 KN computerized universal testing machine (UTM)

with an electronic extensometer. Test was repeated thrice

and the average value was taken to calculate the tensile

strength of the composites.

Details of Universal Testing Machine

Universal testing machine is a Micro Control Systems

make and model MCS-UTE60 and software used is

MCSUTE STDW2KXP. System uses add-on cards for

data acquisition with high precision and fast analog to

digital converter for pressure/Load cell processing and

rotary encoder with 0.1 or 0.01 mm for measuring cross

head displacement (RAM stroke). These cards are fitted

on to slots provided on PC’s motherboard WINDOW9X

based software is designed to fulfill nearly all the testing

requirements. MCS make electronic extensometer is used

with an extremely accurate strain sensor for measuring

the strain of the tensile samples.

3.2. Impact Strength

The Charpy impact strength was carried out on compos-

ites in accordance with ASTM E23 using impact testing

machine. The dimensions of the specimens were 10 mm

× 10 mm × 55 mm size on one side surface of the speci-

men a V-notch have been made at an angle of 45˚ with

root depth of 2 mm. Test was repeated thrice and the ave-

rage values were taken for calculating the impact strength.

3.3. Brinell Hardness Test

Brinell hardness test was conducted on the specimen

Open Access JMMCE

K. DEVENDRA, T. RANGASWAMY 355

using a standard Brinell hardness tester. A load of 250 kg

was applied on the specimen for 30 sec using 5 mm di-

ameter hard metal ball indenter and the indentation di-

ameter was measured using a microscope. The hardness

was measured at three different locations of the specimen

and the average value was calculated. The indentation

was measured and hardness was calculated using Equa-

tion (1).



BHN DDD d





(1)

where: P = Applied force (Kgf); D = Diameter of in-

denter (mm); d = Diameter of indentation (mm).

4. Results and Discussion

Results obtained from this experimental work are pre-

sented in Tables 2-4 and Figures 1-3. Mechanical prop-

erties of fiber-reinforced epoxy composites are depend-

ing on the properties of the constituent materials (type,

quantity, fiber distribution and orientation, void content).

Beside those properties, the nature of the interfacial

bonds and the mechanisms of load transfer at the inter

phase also play an important role.

4.1. Ultimate Tensile Strength

The tensile strength of the E-glass fiber reinforced epoxy

composites depends upon the strength and modulus of

Table 2. Comparison of ultimate tensile strength.

Composite materials Ultimate Tensile Strength, (MPa)

GE 450.24

GEF1 249.80

GEF2 168.80

GEA1 297.80

GEA2 257.21

GEM1 375.36

GEM2 347.20

GEH1 156.92

GEH2 182.30

Table 3. Comparison of Charpy impact strength.

Composite materials Charpy Impact Strength (J/mm2)

GE 0.2846

GEF1 0.2041

GEF2 0.1500

GEA1 0.1681

GEA2 0.1575

GEM1 0.1687

GEM2 0.1625

GEH1 0.1250

GEH2 0.1583

Table 4. Comparison of Brinell hardness numb e r.

Composite materials Hardness (BHN)

GE 57.64

GEF1 39.68

GEF2 37.11

GEA1 73.90

GEA2 82.13

GEM1 88.69

GEM2 88.10

GEH1 46.86

GEH2 54.25

Figure 1. Ultimate tensile strength for different composition

of composite materials.

Figure 2. Charpy impact strength for different composition

of composite materials.

Figure 3. Brinell hardness number for different composi-

tion of composite material.

Open Access JMMCE

K. DEVENDRA, T. RANGASWAMY

356

the fibers, strength and chemical stability of the matrix,

fiber matrix interaction and fiber length.

From the obtained results it was observed that compos-

ite filled by 10% Volume Mg(OH)2 exhibited maximum

ultimate strength of 375.36 MPa when compared with

other filled composites but lower than the un filled com-

posite [Figure 1]. This may be due to good particle dis-

persion and strong polymer/filler interface adhesion for

effective stress transfer. Composites filled by Al2O3 ex-

hibited better ultimate tensile strength compared with

composites filled by fly ash and hematite this is due to that

Al2O3 having the ceramic particles these particles distrib-

uted uniformly throughout the composites and produces

good bonding strength between polymer, filler and fiber.

But increase in addition of Mg(OH)2, Al2O3 and fly ash

content up to 15% volume to the composites the tensile

strengths is found to be less this is due to more filler ma-

terial in the composites damages matrix continuity, less

volume of fiber and more void formation in the composites.

Ultimate tensile strength increases with increase in addi-

tion of hematite to composites this may be due to im-

proved in inter facial bonding strength between filler,

matrix and fiber.

4.2. Impact Strength

Impact strength is defined as the ability of a material to

resist the fracture under stress applied at high speed. The im-

pact properties of composite materials are directly related

to overall toughness and composite fracture toughness is

affected by inter laminar and interfacial strength parameters.

From Figure 2, it is observed that composite filled by

10% volume fly ash having high impact strength when

compared with other filled composites this is due to that

good bonding strength between filler, matrix, fiber and

flexibility of the interface molecular chain resulting in

absorbs and disperses the more energy, and prevents the

cracks initiator effectively. But there was reduction in

impact resistance as the fly ash content increases which

might be because of formation of additional voids and this

void increases the crack propagation. Impact strength de-

creases when increase in addition of Al2O3 and Mg(OH)2

to composites. Typically, a polymer matrix with high

loading of fillers has less ability to absorb impact energy

this is because the fillers disturb matrix continuity and

each fillers is a site of stress concentration, which can act

as a micro crack initiator and reduces the adhesion and

energy absorption capacity of composites. Test results

show that impact strength increases with adding more

hematite powder to composites this due to improvement

of bonding strength between filler and matrix and rigidity

of filler particles absorbs the more energy.

4.3. Hardness

Hardness properties of all the composites are presented

in the Table 4.

The experimental results show that composite filled by

10% volume Mg(OH)2 exhibited maximum hardness

number of 88.69 BHN when compared with other filled

composites this due to uniform dispersion of Mg(OH)2

particles and good bonding strength between fiber and

matrix [6]. From Figure 3, it is observed that increase in

addition of Al2O3 and hematite to composites leads to

increase in hardness number this may be due to the im-

proved bond between the matrix and reinforcement, re-

duced porosity. When increasing the particle loading in

the matrix decreases the inter particle distance with re-

sults in increase of resistance to indentation. Fly ash

filled composites exhibited less hardness number this due

to weak bonding strength and more possibility of void

formation.

5. Conclusions

Based upon the test results obtained from the various

tests carried out, following conclusions were made:

1) From the obtained results, it was observed that com-

posite filled by 10% volume of Mg(OH)2 exhibited maxi-

mum ultimate strength of 375.36 MPa when compared

with other filled composites. Composites filled by Al2O3

exhibited better ultimate strength compared with com-

posites filled by fly ash and hematite. Increase in addi-

tion of Mg(OH)2, Al2O3 and fly ash to composites leads

to decrease in ultimate tensile strength.

2) Experimental results show that composites were fill-

ed by 10% volume of fly ash having high impact strength

when compared with other filled composites. Composites

filled by 10% volume Al2O3 and Mg(OH)2 exhibited good

impact strength but increase in addition of Al2O3 and

Mg(OH)2 leads to decrease in impact strength. Test re-

sults indicated that impact strength increases with adding

more hematite powder to composites.

3) The experimental results indicated that composite

filled by Mg (OH)2 exhibited maximum hardness number

88.69 BHN when compared with other filled composites.

From the results, it is observed that increase in addition

of Al2O3 and hematite to composites increases the hard-

ness of the composites. Increase in addition of fly ash to

composites leads to decrease in hardness number.

REFERENCES

[1] A. Yasmin and I. M. Daniel, “Mechanical and Thermal

Properties of Graphite Platelet/Epoxy Composites,” Poly-

mer, Vol. 45, No. 24, 2004, pp. 8211-8219.

http://dx.doi.org/10.1016/j.polymer.2004.09.054

[2] N. Hameed, P. A. Sreekumar, B. Francis, W. Yang and S.

Thomas, “Morphology, Dynamic Mechanical and Ther-

mal Studies on Poly(styrene-co-acrylonitrile) Modified

Epoxy Resin/Glass Fibre Composites,” Composites Part

Open Access JMMCE

K. DEVENDRA, T. RANGASWAMY

Open Access JMMCE

357

A, Vol. 38, No. 12, 2007, pp. 2422-2432.

http://dx.doi.org/10.1016/j.compositesa.2007.08.009

[3] R. N. Rothon, “Mineral Fillers in Thermoplastics: Filler

Manufacture and Characterization,” Advances in Polymer

Science, Vol. 139, 1999, pp. 67-107.

[4] Cs. Varga, N. Miskolczi, L. Bartha and G. Lipoczi, “Im-

proving the Mechanical Properties of Glass-Fibre-Rein-

forced Polyester Composites by Modification of Fibre

Surface,” Materials and Design, Vol. 31, 2010, pp. 185-

193.

[5] M. Single and V. Chawla, “Mechanical Properties of

Epoxy Resin-Fly Ash Composite,” Journal of Minerals

and Materials Characterization and Engineering, Vol. 9,

No. 3, 2010, pp. 199-210.

[6] R. K. Goyal, A. N. Tiwari and Y. S. Negi, “Micro Hard-

ness of PEEK/Ceramic Micro- and Nano Composites:

Correlation with Halpin-Tsai Model,” Materials Science

and Engineering, Vol. 491, No. 1-2, 2008, pp. 230-236.