Journal of Minerals and Materials Characterization and Engineering, 2013, 1, 353-357
Published Online November 2013 (
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
Received September 2, 2013; revised October 17, 2013; accepted October 28, 2013
Copyright © 2013 K. Devendra, T. Rangaswamy. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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
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-
Glass Fiber
(Volume %)
(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
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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).
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.
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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
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.
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