1. Static and dynamic mechanical analyses of
E-glass–polyester composite used in mass
transit system
Somanath Ojha PhD
Research Scholar, Department of Mechanical Engineering, Durban
University of Technology, Durban, South Africa; Junior Research Fellow,
School for Advanced Research in Petrochemicals, Laboratory for Advanced
Research in Polymeric Materials, Central Institute of Petrochemicals
Engineering and Technology, Bhubaneswar, India
Himanshu Bisaria PhD
Project Scientist, School for Advanced Research in Petrochemicals,
Laboratory for Advanced Research in Polymeric Materials, Central Institute
of Petrochemicals Engineering and Technology, Bhubaneswar, India
(corresponding author: himanshubisaria20@gmail.com)
Smita Mohanty PhD
Principal Scientist and Director-Head, School for Advanced Research in
Petrochemicals, Laboratory for Advanced Research in Polymeric Materials,
Central Institute of Petrochemicals Engineering and Technology,
Bhubaneswar, India
Krishnan Kanny PhD
Senior Director, Department of Mechanical Engineering, Durban University
of Technology, Durban, South Africa
Composite materials have distinct properties such as a high strength-to-weight ratio, high corrosion resistance, a
high modulus-to-weight ratio and wear resistance. The potential, strong mechanical properties and lower cost of E-
glass fiber motivated the authors to carry out this work. Tensile, flexural and Izod impact tests were used in the
current study to conduct a static analysis of an E-glass-reinforced isophthalic polyester composite and an E-glass-
reinforced general-purpose (GP) or orthophthalic polyester composite. The thermal–mechanical behavior was
investigated using thermogravimetric analysis and dynamic mechanical analysis tests. Furthermore, the surface
morphology of the tested composites was examined using scanning electron microscopy (SEM). When compared
with the E-glass-reinforced GP polyester composite, the E-glass–isophthalic polyester composite demonstrated
superior flexural properties and thermal stability. However, the tensile and impact properties of the E-glass–GP
polyester composite were found to be higher than those of the E-glass–isophthalic polyester composite. SEM images
show fiber pullout, matrix cracking and fiber breakage, among other things. The loss modulus and damping values
of the E-glass-reinforced GP polyester composite were found to be greater than those of the E-glass-reinforced
isophthalic polyester composite. The current composite can be used in marine applications, particularly the hull
frame or body of the boat.
Keywords: DMA/E-glass fiber/GP resin/isophthalic resin/mechanical testing/scanning electron microscopy/TGA
Notation
Ac cross-sectional area
b width of the specimen
d thickness of the specimen
EL loss modulus
ES storage modulus
F failure load (N)
Fmax maximum force (N)
Tg glass transition temperature
tan d damping
X span length (mm)
1. Introduction
Materials science progress has resulted in numerous new and
advanced materials. One of them is composites, which are used in a
variety of design applications.1
The concept of composite materials
is not new: joining different materials to create a new material with
properties not possible with the individual constituents.2
In general,
a composite material is a combination of a continuous phase (i.e.
matrix) and reinforcement fibers, sheets or particles.3
The demand
for materials with a remarkable combination of properties has
increased in recent years. Fiber-reinforced polymer composites
(FRPCs) are a new type of composite material that uses fiber and
polymers to make a composite.4
In FRPCs, the matrix makes up a
sizable portion of the polymer composite and serves a variety of
fundamental functions, including holding the reinforcement
together, maintaining the condition of a part and transferring
applied loads to the reinforcement fibers. Glass fibers are
commonly used as reinforcing fibers in polymer matrix composites.
Glass fibers have numerous desirable properties, including low cost,
high chemical resistance, superior mechanical properties and
exceptional insulating properties. Because of their mechanical
properties and better compatibility with the polymer matrix, E-glass
fibers are the most commonly used glass fiber by plastic industries.5
Polyester resins are the most widely used resin systems, particularly
in marine applications. This resin system is used in the vast
majority of composite dinghies, yachts and workboats.6
Polyester
resins are a well-known and widely used matrix material in glass-
fiber-reinforced polymer composites used in oceanic applications.7
Polyester resins are divided into five classes based on their
structural characteristics: ortho resins, vinyl ester resins, isoresins,
bisphenol A fumarates and chlorendics. Ortho resins, also known as
1
Cite this article
Ojha S, Bisaria H, Mohanty S and Kanny K
Static and dynamic mechanical analyses of E-glass–polyester composite used in mass transit
system.
Emerging Materials Research,
https://doi.org/10.1680/jemmr.22.00092
Research Article
Paper 2200092
Received 18/05/2022; Accepted 22/11/2022
ICE Publishing: All rights reserved
Emerging Materials Research

2. general-purpose (GP) resins, are made from phthalic anhydride,
maleic anhydride (MA) or fumaric acid, as well as glycols.
Isophthalic acid, MA/fumaric acid and glycol are used to make
isophthalic resins.8
The utilization of unsaturated polyester resins
are used in vast sectors such as transportation, electrical machines
and building and roads because of advancement of mass- and
sheet-forming compounds utilizing glass fibers.8
From unsaturated
polymer resin, the typical applications of isophthalic resins are
chemical tanks, chemical pipelines, fume extractors, ducts, hoods,
bathtubs and so on, whereas the applications of orthophthalic GP
resin include automobile components, flower pots, sports safety
equipment and helmets. Glass-fiber-based polyester composites
have been the primary material used in the recreational boating
industry as hulls with the fewest assembled parts. These composites
have become popular in pleasure craft because of their high
corrosion resistance, vibration dampening, light weight, impact
resistance, low costs and ease of manufacturing, maintenance and
repair.9
Bhat et al.7
the investigated mechanical and morphological
properties of an isophthalic polyester matrix composite reinforced
with glass fiber. The authors evaluated the mechanical properties
of tensile strength, flexural strength and Barcol hardness, in
addition to carrying out a morphological test, of tensile fractured
specimens of 6, 8 and 10 mm. The tensile failure modes showed
that the strength, and hence the failure of delamination, increases
with an increase in thickness. Besides the mechanical properties,
the authors also explained the different failure modes of the
polymer matrix composite during tensile tests according to the
ASTM D 3039 standard, which depicted the failure type/failure
area/failure location. Miah et al.10
studied the mechanical
behavior and surface morphology of glass fiber–epoxy composite
affected by toughening of unsaturated polyester. The composite
samples subjected to mechanical testing of tensile strength,
compressive strength, shear, hardness and impact were prepared
by blending through the vacuum bag molding process three
different epoxy–polyester composites that had been prepared by
using ultrasonicators. The evaluated results were compared with
those of epoxy and polymers, and it was summarized that the
addition of polyester in the epoxy increases the hardness as well
as fracture toughness to values higher than those of the neat
matrix specimens. Gopinath et al.11
reinforced specimens made of
E-glass, jute and coconut fibers prepared with polyester and
epoxy resin matrices. The pre-arranged specimens were subjected
to mechanical and microstructural studies. The E-glass-reinforced
epoxy resin composites showed better mechanical properties than
the jute-fiber-reinforced composites and coconut-fiber-reinforced
composites. Sivakandhan et al.12
evaluated the mechanical
properties of natural ridge gourd fiber with polymer laminates
prepared with different combinations of fiber and resin by using
the hand layup process. With various structures of patterns
materials characteristics is observed that with different
combinations glass, ceramic fibers with ridge gourd with epoxy
resin and polyester resin laminates increases its mechanical
properties. Sivasaravanan et al.13
compared the mechanical
properties of different grades of epoxy mixed with aloe vera fibers
for fabricating composites by using the hand layup process.
Different grades of epoxy such as LY556 and GY250 were added
with the hardener HY 951 for composite fabrication. It was
observed that the tensile and flexural strengths of epoxy GY250
was better than those of epoxy LY556. Adem et al.14
performed
comparative analysis of the mechanical properties of E-
glass–epoxy composites and E-glass–polyester composites. The
shear, flexural and compressive properties of the E-glass–epoxy
composite showed an increasing pattern with strain rate; however,
the elasticity diminishes as the strain rate increases. For the E-
glass–polyester composite, the compressive and tensile strengths
increase with the strain rate and the in-plane shear and flexural
strengths show a diminishing pattern as the strain rate increases.
Scanning electron microscopy (SEM) micrographs of both epoxy
and polyester composites show fiber pullout and delamination.
Arputhabalan et al.15
performed comparative analysis of the
mechanical properties of various natural fibers such as aloe vera,
sisal, kenaf, jute and flax fibers reinforced with two different
matrices such as epoxy LY556 and GY250 polymers. A higher
elongation was noticed for the epoxy GY250 matrix with all types
of fiber reinforcement except sisal fiber as compared to that of the
epoxy LY556 matrix. Kumar et al.16
tested unidirectional (UD)
carbon-fiber-reinforced plastic samples produced by using the
resin infusion technique under a compression load. In-plane shear,
complicated fracture and through-thickness shear fracture were
identified as three types of fracture modes. Kumar et al.17
described that the fracture morphology of a UD carbon-fiber-
reinforced plastic composite grows as the crack progresses under
tensile loads, similar to the fractographic features seen in
aerospace composites that failed under tensile loads. Srinivasa
et al.18
discussed compression loading on carbon-fiber-reinforced
plastic composite laminates and conducted a fractography
research on fractured specimens using a scanning electron
microscope. Karvanis et al.19
performed a comparative study of
glass fiber polymer composites and carbon fiber polymer
composites by dynamic mechanical analysis (DMA) and
concluded that the storage modulus of the composites decreases
as the temperature rises, with the exception of a very small
increase at low temperatures for some of the compounds. The
composite with the highest storage and loss modulus had UD
glass fibers in the longitudinal direction, accounting for 34% of
the matrix. Bashir20
explained that the peak value of tan d is
lower when there are strong interfacial connections between the
filler particles and the polymeric matrix than when the polymer is
filled and there are weak interactions. Manjunath et al.21
carried
out DMA and revealed the gradual loss of dynamic modulus
properties in a polyester–epoxy composite during the transition
phase. The higher glass transition temperatures and lower tan d
values confirm the ability of the polyester–epoxy composites to
perform well at higher temperatures while resisting impact loads.
Based on these findings, it is possible to conclude that
polyethylene terephthalate–epoxy composites can be used as a
new engineering material in the design of lightweight and impact-
resistant composite structures. Swain et al.22
explained that the
2
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
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3. thermal stability of a hybrid composite was higher than that of
non-hybrid composites, as confirmed by the residue obtained in
thermogravimetric analysis (TGA). Hossain et al.23
studied the
thermal aging of an unsaturated polyester composite reinforced
with an E-glass non-woven mat. According to the experiment, the
heat treatment significantly improved the mechanical properties of
the created composite. A sample that was heated to 90°C had a
maximum tensile strength of 200.6 MPa.
According to the literature review, the majority of studies focused
on the effect of fiber content on mechanical properties, but the
effect of the matrix GP and isophthalic polyester) with E-glass
fiber is rarely studied by researchers. In this work, a comparative
study of the mechanical properties, thermal–mechanical properties
and surface morphology of an E-glass-reinforced isophthalic
polyester composite and an E-glass-reinforced GP polyester
composite was attempted. The composites were fabricated by
using the hand layup technique. In the mechanical
characterization, tensile test, flexural test and impact test of both
composites were conducted. TGA was conducted to study the
thermal–mechanical stability of the composites. A DMA test was
carried out to examine the viscoelastic properties of the
composites. The morphology of tested samples was analyzed
using SEM to study their inhomogeneity, porosity and fracture
behavior.
2. Materials and methodology
2.1 Materials
In this experimental study, the material was procured from Ruia
Chemicals Pvt. Ltd, Kolkata. E-glass fiber (chopped strand mat
450 g/m2
) as a reinforcement and isophthalic polyester and GP
polyester resins as a matrix were utilized for composite
fabrication. The physical and mechanical properties of E-glass
fiber, GP and isophthalic polyester resin are given in Table 1.
2.2 Methodology
2.2.1 Preparation of composites
The hand layup technique was used for fabricating E-glass-fiber-
reinforced GP polyester and isophthalic polyester composites.
Polyester resin was cured at 30°C for 6 h by mixing in 10%
lithium pigment followed by addition of 2 vol.% methyl ethyl
ketone peroxide (MEKP) as a catalyst and 2 vol.% cobalt octoate
as an accelerator for making the polymer matrix. The mixture was
manually stirred to disperse the resin and hardener in the matrix.
For fabricating the composites, a stainless steel frame of
dimensions 1000 mm × 500 mm was utilized with the essential
thickness. A silicon spray was utilized to work with simple
expulsion of the composite from the shape in the wake of
relieving. The composites were subjected to static compression
under a load of 50 kg for 8 h before they were taken out of the
mold. The specimens were cut using an electronic cutter from the
fabricated sheet as per the required ASTM standard. Details of
the materials used in the fabrication of composites are
summarized in Table 2. After fabrication of the composites,
mechanical tests (tensile/flexural/impact) of the fabricated
composites were carried out. All the mechanical tests were
conducted in a standard laboratory atmosphere of 23 ± 2°C and
50 ± 10% relative humidity. Five separate specimens of E-
glass–isophthalic polyester composite (S1) and E-glass–GP
polyester composite (S2) for individual tests were tested, and the
average value was utilized for analysis.
2.2.2 Tensile test
The tensile specimens were cut into rectangular cross-sections
with dimensions of 200 mm × 25 mm × 5 mm according to the
standard ASTM D 3039 and tested using an Instron 3382
universal testing machine (UTM). The test was conducted with a
span length of 110 mm and at a strain rate of 5 mm/min. Five
specimens were tested, and the tests were repeated multiple times.
Then, the average value of results was considered for analysis.
Table 2. E-glass-reinforced polyester composite fabrication
Composite designation Resin Accelerator Catalyst hardener Resin-to-hardener ratio FRP-to-resin ratio
S1 Isophthalic 2% cobalt octoate 2% MEKP 50:1 1:2.25 (seven layers)
S2 GP 2% cobalt octoate 2% MEKP 50:1 1:2.25 (seven layers)
FRP, fiber-reinforced polymer
Table 1. Properties of E-glass fiber, GP and isophthalic polyester8,24,25
Property E-glass GP polyester resin Isophthalic polyester resin
Density: g/cm3
2.58 1.12 1.14
Tensile strength: MPa 3100–3800 55 75
Flexural strength: MPa — 80 130
Tensile modulus: GPa 73 3.45 3.38
Flexural modulus: GPa — 3.45 3.59
Elongation at break: % 4.7 2.1 3.3
Compressive strength: MPa 1080 — —
Heat distortion temp.: °C — 80 90
Hardness (Barcol) — 45 40
3
Emerging Materials Research Static and dynamic mechanical analyses
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mass transit system
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4. The tensile strength or ultimate tensile strength of the samples
was determined for the maximum value of load carried before
failure by using the equation
tensile strength ¼
Fmax
Ac
1.
where Fmax is the maximum force (N) and Ac is the cross-
sectional area.
2.2.3 Flexural test
The specimens for flexural testing were prepared in dimensions of
127 mm × 12.7 mm × 5 mm according to the ASTM D 790
standard.16,26
The three-point bending test was carried out using
an Instron 3382 UTM, and the rate of the applied load was
1.30 mm/min with a span length of 100 mm. In this test, two
points supported the specimen and at a third point, a gradual load
is applied the on specimen up to the fracture point. For each
composition, the tests were repeated multiple times and their
average value was considered for analysis. The calculation of
flexural strength and modulus was carried out by using Equations
2 and 3, respectively.
flexural strength ¼
3FX
2bd2
2.
flexural modulus ¼
mX3
4bd3
3.
where F is the failure load (N); X is the span length (mm); d and
b are thickness and width of the specimen used in flexural test,
respectively; and m is the slope of the initial straight line of the
load-against-deflection graph.
2.2.4 Impact test
The impact test was conducted with an Izod impact tester (Tinius
Olsen) with dimensions of 63.5 mm × 12.7 mm × 5 mm according to
the ASTM D 256 standard.27
During the experiment, the specimen
was placed at the bottom, and when the pendulum, which had a
knife edge, was released, it struck and fractured the specimen at the
notch. The estimated energy consumed was shown on the dial
indicator, and the energy consumed was utilized in the calculation of
the impact strength. The impact strength was calculated by dividing
the impact energy by the thickness of the specimen.
2.2.5 TGA
The thermal stability of the composites was examined through a
TGA test, which were performed using a TGA Q50 device
according to ASTM E 1131.28
The TGA test was carried out on a
sample with a 15–25 mg size and put in a platinum container and
heated in the temperature range 30–800°C. The heating rate and
the rate of flow were 10°C/min and 20 ml/min, respectively, in a
nitrogen (N2) atmosphere.
2.2.6 Morphology
SEM was utilized to reveal the surface morphology of the
composites. SEM micrographs were used to inspect the bonding
and breaking of the fiber and matrix in the composite. The surface
morphology was inspected using a Zeiss JSM-5200 microscope at
×500 magnification.
2.2.7 DMA
In FRPCs, the viscoelastic behavior depends on the
reinforcement, matrix and matrix–fiber interface. For studying the
viscoelastic behavior of the E-glass-reinforced polyester
composite, the DMA test was conducted with a DMA Q800
instrument. The test was performed on samples of dimensions
50 mm ×13 mm × 3 mm as per the standard ASTM D 541829
at a
bending mode frequency of 1 Hz. The temperature was varied
from room temperature to 200°C at a heating rate of 10°C/min.
The viscoelastic properties such as loss modulus, storage modulus
and damping parameters were examined after the test.
3. Results and discussion
3.1 Tensile properties
The samples after the tensile test for the S1 and S2 composites are
shown in Figure 1. The average values of the tensile strengths and
tensile moduli of the tested samples of the S1 and S2 composites
are plotted in Figure 2. The tensile strength and tensile modulus
of the S2 composite were found to be higher than those of the S1
composite. The tensile strength and tensile modulus of the S2
composite were found to be 19 and 5% higher than those of the
S1 composite. The better tensile strength and tensile modulus of
the S2 composite can be explained due to the fact that the E-
glass-fiber-reinforced GP polyester composite, having a low
elongation, may break first and then the load is carried by the E-
glass fiber. However, the isophthalic polyester composite has high
elongation without failure of the matrix, inducing better stress
transfer from the matrix to the fibers and thus resulting in
improved mechanical properties of the S2 composite. Similar
S1
1 2 3 4 5
S2
1 2 3 4 5
(a) (b) (c)
Figure 1. Testing of tensile specimens: (a) testing machine; (b) S1
and (c) S2 composites
4
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
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5. findings were reported by Rao et al.30
from mechanical testing of
an E-glass and polyester resin composite.
The different tensile failure modes obtained for the S1 and S2
composites are given in Tables 3 and 4, respectively. The different
fracture modes and fracture locations were observed for individual
specimens of the S1 and S2 composites. In accordance with
ASTM D 3039,31
the different failure types are designated as
follows: A, angled; D, edge delamination; G, grip; L, lateral; M,
xyz (multimode); S, long splitting; and X, explosive. Meanwhile,
the failure areas are coded as follows: I, inside grip; A, at the
grip; W, <1W from the grip/tab; G, gauge; M, multiple areas; V,
various; and U, unknown. In a similar manner, the failure location
are represented as follows: R, right; L, left; B, bottom; T, top; M,
middle; V, various; and U, unknown. The probable reason for
failure of the sample at the top is the formation of a main chap,
which causes stress concentration at the top and end portions.
Most of specimens failed due to explosive failure, which mainly
occurred by delamination of the fiber and matrix. The angular
failure is due to the anisotropic behavior of the composite.
The grip and gauge are common failure areas for all types of
specimens. The reason for failure at the grip may be local damage
because of the stress concentration generated by high clamping
force.7
3.2 Flexural properties
Figure 3 shows the tested samples for the flexural test for the S1 and
S2 composites. The flexural strengths and flexural moduli of the
tested S1 and S2 composites are plotted in Figure 4. The flexural
strength and flexural modulus of the S1 composite were higher as
compared with those of the S2 composite. The flexural strength and
flexural modulus of the S1 composite were 18 and 27% higher than
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
0
20
40
60
80
100
120
140
160
180
S1 S2 Tensile
modulus:
GPa
Tensile strength
Tensile
strength:
MPa
Tensile modulus
Figure 2. Tensile strengths and tensile moduli of the S1 and S2
composites
Table 4. Details of tensile failure of E-glass–GP polyester
composites
Specimen
number
Mode of
failure
Failure
type
Failure
area
Failure
location
1 GAT Grip At the
gauge
Top
2 XGM Explosive Gauge Middle
3 AIB Angular Inside
grip
Bottom
4 XGB Explosive Gauge Bottom
5 XAM Explosive At the
gauge
Middle
Table 3. Details of tensile failure of E-glass–isophthalic polyester
composites
Specimen
number
Mode of
failure
Failure
type
Failure
area
Failure
location
1 LAB Lateral At the
gauge
Bottom
2 XGT Explosive Gauge Top
3 GAT Gauge At the
grip
Top
4 SGB Long
splitting
Gauge Middle
5 XGM Explosive Gauge Middle
S1 S2
(a) (b) (c)
Figure 3. Flexural testing of specimens: (a) testing machine; (b) S1
and (c) S2 composites
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
0
20
40
60
80
100
120
140
160
180
200
220
240
S1 S2
Flexural
strength:
MPa
Flexural
modulus:
GPa
Flexural strength
Flexural modulus
Figure 4. Flexural strengths and flexural moduli of the S1 and S2
composites
5
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
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6. those of the S2 composite. The S1 composite shows better flexural
strength and flexural modulus as compared with S2 due to the effect
of strong reinforcement with E-glass fiber and an isophthalic
polyester matrix. The reason for better flexural properties as
compared with the tensile properties can be explained due to the fact
that in a flexural test, the application of the load is at a point where
the least number of imperfections is conceivable, while in a tensile
test, the application of the load is over a longer length, a where large
number of defects is conceivable.
3.3 Impact properties
The impact test samples after experimentation are shown in
Figure 5. The impact strengths and impact energies of the S1 and
S2 composites are plotted in Figure 6. Similar to tensile
properties, the impact strength and impact energy were also found
to be maximum for the S2 composite. The impact strength of the
S2 composite is 18% higher than that of the S1 composite. The
mechanical properties of the S1 and S2 composites are compared
with those from already published works on glass and polyester
composites in Table 5.
3.4 TGA
Figure 7 shows the TGA curves of the S1 and S2 composites. The
TGA curves of the composites can be explained as having three
major regions of weight loss due to temperature rise. The initial
5% weight loss of the composites S1 and S2 occurs at relatively
low temperatures of 287 and 224°C, respectively. This weight
loss mainly occurs due to the removal of low-volatility
compounds from the fabricated composite. The major weight loss
of ~60% in S1 and ~80% in S2 occurs at a higher temperature.
The details of the TGA results of the S1 and S2 composites are
given in Table 6. The shift to a higher temperature for the S1
composite illustrates its better thermal stability than that of the S2
composite. The values and trend obtained from the TGA plots of
the S1 and S2 composites are in agreement with the work of
Gupta34
on the TGA of a jute/sisal–epoxy hybrid composite.
3.5 Morphology
SEM micrographs present the structures of the fractured surfaces
due to mechanical loading. Figures 8(a) and 8(b) show SEM
S1 S2
(a) (b) (c)
Figure 5. Izod impact testing: (a) impact machine used in impact
testing of specimens; (b) S1 and (c) S2 composites
4.0
4.4
4.8
5.2
5.6
6.0
6.4
6.8
800
840
880
920
960
1000
1040
1080
1120
S1 S2
Impact
energy:
J
Impact strength
Impact
strength:
J/m
Impact energy
Figure 6. Impact strengths and impact energies of the S1 and S2
composites
Table 5. Comparison of mechanical properties of the fabricated composites with those from published works
Fiber Matrix
Tensile
strength: MPa
Tensile
modulus: GPa
Flexural
strength: MPa
Flexural
modulus: GPa
Impact strength:
J/m
Reference
E-glass Isophthalic
polyester
117.51 3.13 323.73 — — Bhat et al.7
E-glass Vinyl ester 120 — — — — Suresh
et al.32
E-glass Polyester 28.87 2.406 102.27 6.391 — Gopinath
et al.11
Glass Polyester 118.14 2.17 — — — Rao et al.30
Mat glass Polyester 99.4 — 127.1 2.28 — Varga
et al.33
Woven
glass
Polyester 197 — 63.3 1.86 — Varga
et al.33
E-glass GP polyester 149.63 ± 5.73 1.98 ± 0.19 163.25 ± 24.95 4.584 ± 0.05 1007.006 ± 14.04 Present study
E-glass Isophthalic
polyester
125.757 ± 5.69 1.86 ± 0.24 193.02 ± 13.63 6.22 ± 0.20 877.82 ± 13.65 Present study
6
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
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7. micrographs of fractured tensile samples of the S1 and S2
composites, respectively. Due to tensile loading, fiber breakage
and matrix cracking in the S1 and S2 composites can be easily
noticed. Uneven matrix surfaces and fiber pullout can also be
clearly seen in the SEM images.
3.6 DMA
The variation in the viscoelastic properties of the S1 and S2
composites such as storage modulus (ES), loss modulus (EL) and
tan d with temperature is shown in Figures 9(a)–9(c). The storage
modulus of a material may be defined as the energy stored by it
during one cycle of oscillation. Figure 9(a) shows the effect of
temperature on the storage moduli of the S1 and S2 composites at
a 1 Hz frequency. It can be observed from the graph that the value
of ES for the S1 composite (0.2898 GPa) was higher than that of
the S2 composite (0.2816 GPa) in the glass transition region. For
both composites, the curve falls steeply with the increase in
temperature and appears to be merged after the glassy plateau
temperature, which may occur due to the softening interfacial
effect at elevated heat. The loss modulus is the amount of energy
lost in the form of heat from materials during one cycle of
oscillation. Figure 9(b) shows the effect of temperature on loss
modulus at a 1 Hz frequency for the S1 and S2 composites.
Damping (tan d) may be defined by the ratio of ES to EL. The
value of tan d demonstrates the damping properties of the
material. Figure 9(c) shows the variation in damping (tan d) with
temperature at a 1 Hz frequency for the S1 and S2 composites.
The value of Tg obtained from the loss modulus curve and
damping curve was found to be higher for the S1 composite as
compared with that of the S2 composite. The higher value of tan d
for the S2 composite signifies its better damping properties. The
valued of Tg obtained from the tan d curve was found to be higher
as compared to that from the loss modulus curve for both the S1
and S2 composites. The glass transition temperatures obtained
from the loss modulus curve and damping curve and the
corresponding peak heights are summarized in Table 7. Similar
findings were reported by Saxena and Gupta35
for the DMA a
0
20
40
60
80
100
120
0 100 200 300 400 500 600 700 800 900 1000
Weight
loss:
%
Temperature: °C
S1
S2
Figure 7. Effect of temperature on the weight losses of the S1
and S2 composites
(a) (b)
Matric
cracking
Uneven matric
surface
Matric
cracking
Fiber breakage
Fiber breakage
Fiber pullout
Fiber pullout
Fiber pullout
Mag. = ×500
20µm EHT = 5.00kV
WD = 13.49mm
Signal A = SE1
Photo no. = 1419
Date: 6 Apr 2022
Time: 10:18:06
Mag. = ×500
20µm EHT = 5.00kV
WD = 14.56mm
Signal A = SE1
Photo no. = 1417
Date: 6 Apr 2022
Time: 10:13:44
Figure 8. Surface morphology of the tested samples: (a) S1 and (b) S2 composites
Table 6. TGA of E-glass-reinforced GP and isophthalic polyester composites
Composite
Degradation temperature at 5%
weight loss: °C
Max. weight loss
rate: %/°C
Temperature at max. weight loss
rate: °C
End residual
mass: %
S1 287.78 0.9495 402.28 31.50
S2 224.07 1.0760 401.63 17.64
7
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

8. hybrid wood composite. Singh et al.36,37
also reported similar
findings for the DMA of epoxy-based nanocomposites.
4. Conclusions
In this experiment work, a comparative study of the mechanical
properties of E-glass-reinforced GP polyester and isophthalic
polyester composites was carried out. Based on the obtained
results, the following conclusions can be made.
■ The tensile strength and tensile modulus of the E-glass-
reinforced GP polyester composite were found to be higher
than those of the E-glass-reinforced isophthalic polyester
composite. The tensile strength and tensile modulus of the S2
composite were approximately 19 and 5% higher as compared
with those of the S1 composite, respectively, which shows the
strong bonding between E-glass and the GP polyester matrix.
■ The flexural properties of the S1 composite were improved as
compared with those of S2. The flexural strength and flexural
modulus of the S1 composite were enhanced by 18 and 27%
as compared with those of the S2 composite, respectively.
■ The S2 composite shows better impact strength (1007 J/m)
than the S1 composite (877 J/m).
■ TGA shows the better thermal stability of the S2 composite as
compared with that of the S1 composite.
■ The SEM micrograph of the fractured surface reveals fiber
breakage, matrix cracking and fiber pullout after the tensile test.
■ At higher temperatures, the storage moduli of the S1 and S2
composites were found to decrease because of loss in
stiffness. The value of the loss modulus as well as that of
damping was found to be high for the S1 composite. For both
the S1 and S2 composites, the value of the glass transient
temperature (Tg) obtained from the tan d curve was found to
be higher than that obtained from the loss modulus curve.
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0 25 50 75 100 125 150 175 200 225 250
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Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

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9
Emerging Materials Research Static and dynamic mechanical analyses
of E-glass–polyester composite used in
mass transit system
Ojha, Bisaria, Mohanty and Kanny
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution