terials are frequently used materials now days in engineering applications.
In the present research work similar attempt is made to study the effect of
silicon di-oxide (SiO2) as filler on mechanical behaviour of glass
fiber reinforced epoxy composites, in primary and advanced applications. This
study shows that the addition of SiO2 into GFRP composites has
increased its mechanical properties. Scanning electron microscope (SEM), a
morphological analysis was carried out to observe the bonding between matrix
and reinforcement and also clearly indicates the mode of failure in the
combination of crack in matrix, fiber debonding and fiber pullout for all types
Keywords—Epoxy, Glass fiber, Silicon di-oxide (SiO2),
Mechanical properties and SEM analysis.
Glass fiber reinforced polymer matrix composites have been
extensively used in in various field such as aerospace, marine, industries,
automobiles, defense etc. a possibility that the incorporation of both
particles and fibers in polymers could provide a synergism in terms of improved
properties and performance has not been adequately explored so far. However
certain current reports suggest that by incorporating micro hard filler into
the polymer matrix of fiber reinforced composites. The current paper is to
mechanical properties and SEM studies on glass-epoxy based composites with
glass fabrics made of 360 g/m2 containing E-glass fabric of diameter
12µm. The epoxy resin was mixed with the hardener (HY 951) in the ratio of
100:12 by weight; hardener is used in curing of composites due to many
applications. The filler chosen is silicon di-oxide (SiO2) using as
a coupling agent and particle size 15-20µm. The details of mechanical
properties of constituent are selected for present work shown in Table 1.
The specimens are prepared by
hand layup process. To prepare laminates with filler, calculated amount of
epoxy resin is weighed and taken in a separate container in calculated
quantity. Once the materials are prepared for fabrication the next step is to
prepare the composite plates using hand layup procedure. This procedure is
carried out for three different compositions 0%, 5%, 7.5%, 10% of SiO2 and
glass-epoxy. The composite plates are cured at temperature of 80-900C and which is maintained at a
temperature of 800C, to improve mechanical properties of composite
plates. Composite material fabricated is machined into dimensions of length
Composition of materials for required for fabrication of composites
fabric weight (gm)
Hardener weight (gm)
weight of the plate (gm)
Fig 1: shows the hand lay-up procedure carried out for Glass epoxy
Testing of mechanical
properties of composite materials mainly depends upon the direction of fiber
oriented is different in different direction.
3.1 Tensile properties
Tensile strength is amount of material
strength to resist pull. Tensile strength is also the measurement of materials
strength when force is functional in two opposite direction.
Fig 2: Tensile tested specimens
can be used to obtain the material characteristics such as brittleness or
According to this standard the dimensions of the specimens should be 165*19*3mm,
below mentioned figure shows the dimensions of the specimen.
3.2 Flexural properties
This test comes under
destructive test method; it is also called as three point bending test. In this
test the specimens are in rectangular or circular shape and transverse bending
load is usually applied. The flexural strength gives the maximum stress within
the experienced within the material and its moment of failure. The specimen prepared and tested according
to ASTM D-790 standards. According
to this standard the dimensions of the specimen should be as of 80*8*3mm in
Fig 3: Flexural tested specimens
The felxural strength
and flexural modulus can be calculated as follows:
strength = 3FL
modulus = ML3
This test measures the resistance of the
specimens for suddendly applied loads. There are two methods to conduct the
test.The impact test specimens are cut from
the hand laid specimens that are prepared before, the specimens are to be cut
to the ASTM standards for impact testing, here in this operation the impact
testing is of two types, one is izod testing and the other is charpy testing,
the testing for this specimen is done according to the charpy testing. The specimen
is then cut from the plate of dimensions of ASTM standards of ASTM-D256, the
dimensions of this standard is 65*12.5*3mm in dimension.
Fig 4: Impact tested
Impact strength =E/t x 1000
E = Energy used to break (J)
t = Thickness (mm)
Results and Discussion
of mechanical properties
The mechanical properties such as density,
tensile strength, flexural strength, shear
strength, impact strength and elongation at break of unfilled and SiO2 filled
glass epoxy composites are listed in table 2.
4.1 Evaluation of mechanical
The mechanical properties such as density, tensile
strength, flexural strength, shear strength, impact strength and elongation at
break of unfilled and SiO2 filled glass epoxy composites are listed in
Table 2: Mechanical testing
results of composites
Tensile 0Strength (MPa)
Impact 0Strength (J)
4.2 Variation of density
Fig 5: Density variations
all density variation graphs, it is observed that the density increases by
increase in filler percentage because the density of filler (SiO2)
is greater than resin. It also observes that the
combination of Glass and epoxy shows the lesser density values than compared to
Glass epoxy with SiO2.
4.3 Tensile test results
The tensile strength of the
%SiO2 specimens are shown in above table. From the table
and graph shown above we can conclude that as the filler loading %increases, the tensile strength of the
composite increases it also follow the same trend as that of 0% SiO2 specimens. By the general observation
the tensile stress of these combinations is significantly increasing with
increase in filler loading. The Maximum
tensile strength in the current study is obtained for 10% SiO2-G-E composite and
is establish to be 263.35 MPa, which
is approximately 1.5 times that of neat
Fig 6: Tensile properties of hybrid glass/SiO2
reinforced epoxy composites
4.4 Flexural test results
The flexural strength of the composites
varies from 26.5 to 30.59 N/mm2
and 19.58 to 24.52 N/mm2 and the maximum value is obtained for composite with 10 % of Silicon di oxide (SiO2)
with G- E-SiO2. The above fig shows
that the combination of G-E-SiO2 has
maximum flexural strength and the combination of G-E has minimum flexural strength. As the filler percentage increases the flexural strength of the composites increases. The reduction of flexural strength observed due to increase in filler material and
may be change in matrix properties reduce their strength between fiber and matrix.
Fig 7: Flexural properties of hybrid glass/SiO2
reinforced epoxy composites
4.5 Impact test results
The above graph shows the impact energy observed variation in different filler loading. It is due to the strong
bonding between filler materials and fiber structure. It exhibits higher impact energy observation for the G-E-SiO2 composite
combination compared to G-E composites.
The increase of impact energy in G-J-E
is due to the strong bonding between fiber and the filler material. Compared to all the samples of the composite
measured 7.5% SiO2 filled
Galas-Epoxy composites shows advanced tensile strength followed by 5% and 10% SiO2 filled
and the least strength is unfilled
Fig 8: Impact
strength of hybrid glass/SiO2 reinforced epoxy composites
Scanning Electron Microscope (SEM)
SEM analysis is focused on evaluation of dispersion of
filler in the matrix. Normally SEM pictures are used to find uniform mixing of
filler with resin, dispersion of fillers in the matrix, evaluate the crack
formation, effect of pull out of fiber after applying load etc.
Fig 9: SEM micrographs of fr
The fracture is due to Delamination between two layers of the composite
specimens and fibre pull out (figure a) for glass epoxy sample, the fracture is
ductile brittle and can be explained by plastic deformation of the matrix after
fiber matrix debonding. The SEM micrographs shown in figure b supports this
failure mechanism because the fibres on fractured surfaces are clean, which
shows brittle fracture.
10: SEM image of hybrid 5 wt. % of SiO2 filled glass/epoxy
composites after flexural test
Figure 10 shows
the SEM characterization of the SiO2 filled G–E fractured surface
shows that the fibers are more or less covered with the matrix and SiO2
particles a qualitative indication of a greater interfacial strength.
Disorientation of transverse fibers, fiber bridging, fibers pull out, inclined
fracture of longitudinal fibers, matrix rollers, and matrix cracking is also
Fig 11: SEM image of hybrid
glass/epoxy composites after impact test
In the impact
specimen one can see the trans-laminar crack; the trans-laminar crack means
there is breakage of the specimen surface there is little formation of crack on
the surface. The fibers in the specimens are pulled out in the impact and bend
specimens. The pull out of the fibers are caused due to the weak interface
between the glass fiber and matrix. The laminates that were oriented one above
the other the laminar strengths may be decreased are as seen in the above
The fabrication and experiment of glass fiber reinforced epoxy
composites with addition of silicon di-oxide (SiO2) were
successfully carried out and the results were tabulated along with the compared
Probable replacement of some
earlier component by the fiber reinforced polymer.
Use of multiple fibers hybrid
polymer composites for enhanced properties and applications.
The glass fiber reinforced
epoxy composites shows better mechanical; properties compared to other fibers.
The morphologies of eroded
surfaces hybrid composites with filler addition as observed by SEM.
that overall erosion damage of composite is mainly due to breaking of
of fiber prevented due to good bonding between fiber and matrix.
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