S. SHABBERHUSSAIN, R. VELMURUGAN: INFLUENCE OF GRAPHENE NANOPLATELETS ON MECHANICAL AND ...
419–422
INFLUENCE OF GRAPHENE NANOPLATELETS ON
MECHANICAL AND THERMO-MECHANICAL PROPRTIES OF
GLASS/EPOXY COMPOSITES
VPLIV GRAFENSKIH NANOPLO[^IC NA MEHANSKE IN
TERMO-MEHANSKE LASTNOSTI KOMPOZITOV NA OSNOVI
STEKLA IN EPOKSIDNIH SMOL
S. Shabberhussain, R. Velmurugan
Aerospace Engineering Department, IIT Madras, Chennai, India
Prejem rokopisa – received: 2023-01-18; sprejem za objavo – accepted for publication: 2023-05-08
doi:10.17222/mit.2023.753
The current work focuses on the influence of graphene nanoplatelets (GPs) on the mechanical and thermo-mechanical properties
of unidirectional glass/epoxy (GE) composites. GE and GP-GE composites are fabricated using the hand lay-up method fol-
lowed by compression molding. Different percentages of GPs used in the fabrication of GP-GE composites are (0.1, 0.3, 0.5,
and 0.7) w/% by weight of the epoxy. Tests are conducted to experimentally evaluate the uniaxial compressive properties and the
coefficient of linear thermal expansion (CLTE) in the direction of fibers. Tests are also conducted to study the thermo-mechani-
cal properties such as storage modulus (E’) and loss modulus (E’’). The variation in the storage modulus and loss modulus is
measured from 15 °C to 125 °C, using a dynamic mechanical analyzer (DMA) while the CLTE is measured using a
dialatometer. The results indicate that the compressive as well as thermo-mechanical properties increase with the addition of
GPs up to 0.5 % and then they decrease. The addition of GPs has no effect on the CLTE of the GE composites in the fiber direc-
tion.
Keywords: graphene nanoplatelets, glass/epoxy composites, thermo-mechanical properties, compression, coefficient of thermal
expansion
V ~lanku je opisan vpliv dodatka grafenskih nanoplo{~ic (GP) na mehanske in termomehanske lastnosti usmerjenih kompozitov
na osnovi steklenih vlaken in epoksida (GE). Kompozite tipa GE in GP-GE so izdelali z ro~no tehniko nalaganja, nato je sledilo
oblikovanje pod tlakom. Izbrane koli~ine dodanih grafenskih plo{~ic v kompozitih GP-GE so bile (0,1, 0,3, 0,5 in 0,7) w/%
glede na maso epoksija. Po izdelavi kompozitov so dolo~ili njihove mehanske lastnosti (tla~no trdnosti) in koeficiente
linearnega toplotnega rastezanja (CLTE; angl.: coefficient of linear thermal expansion) v smeri vlaken. Pri testih
termomehanskih lastnosti sta bila dolo~ena tudi modul shranjevanja (E’) in modul izgub (E’’). Oba parametra so dolo~ili v
temperaturnem obmo~ju med 15 °C in 125 °C v dinami~nem mehanskem analizatorju (DMA). CLTE so dolo~ili s pomo~jo
dilatometra. Rezultati preiskav so pokazali, da se tla~ne kot tudi termomehanske lastnosti kompozitov izbolj{ujejo do dodatka
0,5 % grafenskih plo{~ic, nato pa se postopoma slab{ajo. Dodatek grafenskih plo{~ic kompozitom GE ne vpliva na CLTE v
smeri vlaken.
Klju~ne besede: grafenske nanoplo{~ice, kompoziti steklo-epoksidna smola, termomehanske lastnosti, stiskanje, koeficient
linearnega toplotnega rastezanja
1 INTRODUCTION
Fiber-reinforced polymer (FRP) composites, due to
their superior properties such as high strength-to-weight
ratio, high stiffness-to-weight ratio, corrosion resistance
and thermal resistance, have been widely used in differ-
ent industries such as aerospace, marine, construction
and automobile industries, and nuclear power plants. Ad-
ditions of various nanofillers such as carbon nanotubes
(CNTs), nanoclay and GPs tend to improve the perfor-
mance of polymer nanocomposites and fiber-reinforced
epoxy composites under different loading conditions.
Also, the properties of FRP composites are susceptible to
temperature changes.
Graphene oxide, when added to epoxy resin, im-
proved the tensile strength by 11.5 % at 0.3 % and the
flexural strength by 5.8 % at 0.5 % by weight of the ep-
oxy resin.
1
An addition of GPs of less than 0.25 % of the
volume of the epoxy resin caused better tensile modulus,
lap shear and energy release rate as compared to CNTs,
whereas CNTs were found to be effective at relatively
higher volume fractions.
2
The effect of an inclusion of
nonfunctionalized or amine-functionalized reduced
graphene oxide on the mechanical, thermal and electrical
properties of epoxy nanocomposites is reported in refer-
ence.
3
No significant difference in the performance of the
two types of nanofillers was reported. However, an incre-
ment in properties with the addition of nanofillers com-
pared to neat epoxy resin was reported. The effect of
GPs on the CTE of polyetherimide thermoplastic com-
posites is shown in reference.
4
It is reported that the GPs
are very effective in reducing the CTE in the three or-
thogonal directions. The effects of additions of GPs with
different surface areas (300, 500 and 750) m
2
/g on the
Materiali in tehnologije / Materials and technology 57 (2023) 5, 419–422 419
UDK 678.686:544.3.032.2 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 57(5)419(2023)
*Corresponding author's e-mail:
ramanv@iitm.ac.in (R. Velmurugan)

mechanical and thermal performance of mixed silicate
with different ratios of alkali silicates were studied.
5
The
GPs varied from (1, 5 and 10) w/% of the mixed silicate.
It was reported that the lap shear strength increased by
25.6 % with the addition of 10 % of GPs with a surface
area of 750 m
2
/g. It was also reported that the increase in
the surface area of the GPs changed the mixed silicate
from brittle to ductile, leading to a reduction in the hard-
ness compared to the polymer without GPs.
The polypropylene reinforced with short glass fibers
and GPs, either individually or in combination, resulted
in an increment in the mechanical and thermal perfor-
mances.
6
However, the hybrid composite with a simulta-
neous addition of both fillers performed better than the
composites with individual ones. The addition of differ-
ent nanofillers such as CNTs, GPs and the combination
of CNTs and boron nitride nanosheets or CNTs and bo-
ron nitride nanotubes were shown to improve the tensile
and the fracture performance of GE composites.
7
Ther-
mal properties of GE composites were measured experi-
mentally to study the effect of the addition of different
volume fractions of various carbon-based nanofillers
such as graphene oxide, reduced graphene oxide, GPs
and CNTs.
8
Enhancements in the thermal conductivity
by 8.8 % with 0.3 % MWCNTs, 12.6 % with 1 % GPs,
8.2 % with 2 % graphene oxide, and 4.1 % with 0.042 %
reduced graphene oxide were observed. However, with
the same volume fraction of nanofillers, the GPs resulted
in the highest improvement in the properties. Glass/vinyl
ester composites with CNTs were produced using a
high-pressure injection and the addition of 3 % nano-
fillers was shown to improve the thermal conductivity by
1.5 times.
9
It can be found in the literature that the me-
chanical, thermal and thermo-mechanical data available
on the GP-GE composites at different GPs content are
limited. In this context, the current study focuses on ex-
perimental work to investigate the impact of GPs on the
CLTE, compressive and thermomechanical properties
such storage modulus and loss modulus of GE compos-
ites.
2 EXPERIMENTAL STUDY
To experimentally evaluate the effect of an addition
of GPs on the mechanical, thermal and thermo-mechani-
cal properties, GE and GP-GE composites were fabri-
cated using the hand lay-up method followed by com-
pression molding. Commercially available epoxy LY556,
hardener Araldite HY951 and glass fibers having an area
density of 740 g/mm
2
were used for the fabrication. Four
layers of glass-fiber fabric were used for each laminate.
The GPs were procured from PlasmaChem GmbH, hav-
ing a purity of 91 %, a thickness of 1–4 nm, a width of
up to 2 μm, and a specific surface area of
700–800 m
2
/gm.
To prepare a blend of epoxy/GPs, the GPs were ini-
tially added to ethanol and sonicated for one hour. The
mixture was then transferred to a stirrer and shear mixed
at 500 min
–1
for one hour. This ensured the dispersion of
the GPs into ethanol. The epoxy resin was then added to
the ethanol/GPs mixture, which was shear mixed for 6 h
on a hot platform at 70 °C before being utilized in the
fabrication of GP-GE composites using the hand lay-up
method followed by compression molding. The thickness
of each laminate fabricated was around 3.2 mm. The
composite laminates were then cured at room tempera-
ture for 72 h before testing. Specimens of the required
dimensions for various tests were cut using a waterjet
cutting machine. The sizes of compressive, CLTE and
DMA test specimens were (142 × 14) mm, (40 × 10) mm
and (55 × 10) mm, respectively. Thermo-mechanical
tests were performed using a dynamic mechanical ana-
lyzer (DMA) from NETZSCH, Germany. Uniaxial com-
pression tests were performed using a test fixture on a
universal testing machine with a capacity of 400 kN, ac-
cording to ASTM D6641, whereas CLTE tests were per-
formed in a dialatometer.
3 RESULTS
The DMA was used to determine the storage modu-
lus (E’) and loss modulus (E’’) of the GE and GP-GE
S. SHABBERHUSSAIN, R. VELMURUGAN: INFLUENCE OF GRAPHENE NANOPLATELETS ON MECHANICAL AND ...
420 Materiali in tehnologije / Materials and technology 57 (2023) 5, 419–422
Figure 1: Storage modulus (E’) and loss modulus (E’ ’ )o fG Ea n d
GP-GE composites

composites that are given in Figures 1a and 1b. The
analysis was performed under three-point bending from
15 °C to 125 °C at a rate of 5 °C/min and a frequency of
5 Hz. It can be seen from Figure 1a that the storage
modulus increased with the addition of GPs up to 0.5 %
and then decreased with further addition. A similar be-
havior can be observed at the peak of the loss-modulus
curves shown in Figure 1b. The storage modulus of the
GP-GE composites in the pre-glass transition stage (be-
low 70 °C) is higher than that of the GE composites;
however, it is lower for the GP-GE composites in the
post-transition (beyond 80 °C) stage, with 0.1 % and
0.3 % GPs content. The storage modulus at 0.5 % GNs is
30.2 % higher than that of the GE composites at 15 °C.
The glass-transition temperature (T
g
) of the material can
be found from the E’v sT curve. The glass-transition
temperature is the temperature at which composites
change from a glassy to a rubbery phase. The T
g
of the
GE composites is found to be 70 °C. The T
g
value in-
creased with the addition of GPs from 0.1 % to 0.5 %
and then decreased. However, a slight increment in the T
g
value can be observed for the GP-GE composites com-
pared to GE composites.
The stress-strain curves for the GE and GP-GE com-
posites under a compressive load are presented in Fig-
ure 3. The compressive strength is calculated from the
peak load carried by the specimen, whereas the modulus
is obtained from the slope of the stress-strain curve. The
compressive strength and modulus of the GE and GP-GE
composites are given in Table 1. It can be observed that
the compressive strength and modulus of the composites
increase with an increase in the GPs content up to 0.5 %
and then decrease with further addition of GPs. The
compressive strength of the GE composites is found to
be 203 MPa. The strength of the GE composites in-
creases by (10.8, 18.7, 25.1 and 20.7) % with the addi-
tions of (0.1, 0.3, 0.5 and 0.7) % GPs, respectively. The
compressive modulus of the GE composites is 21.9 GPa.
The modulus of the GE composites increases by (6.4,
17.4, 28.8 and 21.5) % with the additions of (0.1, 0.3, 0.5
and 0.7) % GPs, respectively. The reduction in the com-
pressive properties at 0.7 % GPs is due to the agglomera-
tion of nanoparticles at higher contents.
Tests were performed on the dialatometer to study the
effect of the GPs content on the CLTE of the GE com-
posites in the fiber direction from room temperature to
70 °C. The size of the specimens used for measuring the
CLTE was (40 × 10) mm. The CLTE value is dominated
by the property of the glass fibers in the longitudinal di-
rection. Hence, the addition of GPs did not affect the
thermal expansion property of the GE composites in the
fiber direction. The CLTE for the GE and GP-GE com-
posites measured in the fiber direction is found to be
9×10
–6
/°C.
4 DISCUSSION
As GPs allow superior properties, the effects of dif-
ferent weight fractions of GPs on various properties such
as mechanical, thermal and thermo-mechanical proper-
ties of GE composites are analyzed in the current study.
The properties evaluated are the compressive strength,
modulus, CLTE and thermo-mechanical properties in the
flexural mode. The amounts of GPs considered in the
study are (0.1, 0.3, 0.5 and 0.7) % of the weight of the
epoxy resin. GE and GP-GE composites are fabricated
using the hand lay-up method followed by compression
molding. The variation in the storage modulus and loss
modulus is measured from 15 °C to 125 °C at a rate of
5 °C/min and a frequency of 5 Hz. Uniaxial compression
tests are carried out to measure the compressive strength
and modulus of the GE and GP-GE composites. The
CLTE of the GE composites in the fiber direction is mea-
sured by conducting tests on the dilatometer.
5 CONCLUSIONS
The effects of the incorporation of GPs on different
properties such mechanical, thermal and thermo-me-
chanical properties of the GE composites fabricated us-
ing the hand lay-up method followed by compression
molding are studied. The addition of GPs increases the
storage modulus and loss modulus of the GE composites
up to 0.5 % before decreasing. The increase in the prop-
S. SHABBERHUSSAIN, R. VELMURUGAN: INFLUENCE OF GRAPHENE NANOPLATELETS ON MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 57 (2023) 5, 419–422 421
Table 1: Compressive strength and modulus of GE and GP-GE composites
Neat 0.1 % GPs 0.3 % GPs 0.5 % GPs 0.7 % GPs
Strength (MPa) 203 ± 6.6 225 ± 9.4 241 ± 5.6 254 ± 8.5 245 ± 5.9
Modulus (GPa) 21.9 ± 0.22 23.3 ± 0.49 25.7 ± 0.78 28.2 ± 0.92 26.6 ± 0.24
Figure 2: Stress-strain curves for GE and GP-GE composites under
compression

erties is a result of a good distribution of GPs in the GE
composites. The agglomeration of GPs at higher weight
fractions resultes in a reduction in the properties. A simi-
lar behavior is observed for the strength and modulus of
the composites under compression. The addition of GPs
has no effect on the CLTE of the GE composites in the
fiber direction.
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S. SHABBERHUSSAIN, R. VELMURUGAN: INFLUENCE OF GRAPHENE NANOPLATELETS ON MECHANICAL AND ...
422 Materiali in tehnologije / Materials and technology 57 (2023) 5, 419–422