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Original Article
Mechanical performance of woven
kenaf-Kevlar hybrid composites
Journal of Reinforced Plastics
and Composites
0(0) 1–13
! The Author(s) 2014
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DOI: 10.1177/0731684414559864
jrp.sagepub.com
R Yahaya1,2, SM Sapuan1,3,4, M Jawaid3,5, Z Leman1 and
ES Zainudin1,3
Abstract
Hybrid composites offer a combination of advantages of constituent components to produce a material with determined
properties. In the present work, woven hybrid composite was prepared by hand lay-up method in laminate configuration.
Kevlar/kenaf hybrid composites were fabricated with total fibre content of 30% and the ratio of Kevlar/kenaf varies in
weight fraction of 78/22, 60/40, 50/50, 26/74, and 32/68, respectively. The Kevlar/epoxy and kenaf/epoxy were also
prepared for comparison. The mechanical properties of hybrid, kenaf/epoxy, and Kevlar/epoxy composites were tested.
Morphological properties of tensile fracture surface of hybrid composites were studied by scanning electron microscopy.
Results have established that the mechanical properties of kenaf-Kevlar hybrid composites are a function of fibre content.
The hybrid composites with Kevlar/kenaf (78/22) ratio exhibited better mechanical properties compared to other hybrid
composites. This result indicates the potential of Kevlar-kenaf hybrid composite for impact applications.
Keywords
Woven kenaf, Kevlar, hybrid composites, mechanical properties
Introduction
Fibre reinforced polymer composites have been intensively used in various industries such as aerospace,
marine, transportation, and defence because of their
advantages in terms of strength and stiffness.
Nowadays, there are trends in our society towards natures concern. Researchers also show their interest in
using nature-friendly materials in fibre reinforced polymer composites. Natural fibres reinforced polymer
materials have been used in different applications.
Fibres like pinus, sisal, flax, hibiscus sabdariffa, jute,
etc. have all been proved to be good reinforcements
in thermoset and thermoplastic matrices.1,2 Innovative
research was also conducted on other natural fibres
such as saccaharum cilliare fibres,3 pine needle,4
durian skin,5 water hyacinth fibres,6 and many more.
The use of natural fibres as renewable materials in polymer matrix composites will reduce the synthetic petroleum-based fibres, thus preserving the natural resources
and the world as a whole.7 Natural fibres have many
advantages over synthetic fibres such as biodegradable,
low weight, low cost, and acceptable properties.
Natural fibres are now considered serious alternative
to synthetic fibres for use in various fields.8,9 Thakur
and Thakur10 in their review highlighted the advantages natural fibre reinforced polymer composites
such as the easy process, eco-friendly, and environmental awareness which encourage the use of natural fibres.
The recent advances and progress in application of
lignin as bio-renewable polymers was thoroughly
reviewed in Thakur et al.11 Thakur et al.12 reviewed
1
Department of Mechanical and Manufacturing Engineering, Universiti
Putra Malaysia, Serdang, Selangor, Malaysia
2
Science and Technology Research Institute for Defence (STRIDE),
Kajang, Selangor, Malaysia
3
Laboratory of Biocomposite Technology, Institute of Tropical Forestry
and Forest Products (INTROP), Universiti Putra Malaysia, Serdang,
Selangor, Malaysia
4
Aerospace Manufacturing Research Centre (AMRC), Faculty of
Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
5
Department of Chemical Engineering, College of Engineering, King Saud
University, Riyadh, Saudi Arabia
Corresponding author:
SM Sapuan, Department of Mechanical and Manufacturing Engineering,
Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
Email: [email protected]
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the mechanical properties of raw natural fibre-polymer
matrix composites. They concluded that the natural
fibre-based polymer composite offers a number of
advantages over synthetic fibres such as glass fibre,
aramid fibres, and carbon fibre. However, the disadvantages of natural fibres as reported in Khalil et al.13
among others are low modulus, low strength, and poor
moisture resistance compared to synthetic fibre
composites.
Hybridization, a process of incorporating synthetic
fibres with that of natural fibres in order to yield a
hybrid composite with a comparable strength, stiffness,
strength-to-weight ratio, impact resistance, and other
physical and mechanical properties. This type of
hybridization will lead to benefits like reduction of synthetic fibres consumption, less process energy, and concurrently materialised green initiative towards a better
environment. In synthetic–natural fibres hybrid composites, most of the research works aim to reduce the
use of synthetic fibres. Among the research in synthetic–natural fibres hybrid is oil palm/glass,13 pineapple/glass,14 sisal/carbon,15 jute/glass,16 sisal/glass,17
kenaf/glass,18 and sugar palm/glass.19
Properties of kenaf hybrid composites depend on
many factors such as type of fibres (fibre structure–
single fibre, long fibre, random non-woven or woven
structure).20 Based on literature study, only limited studies are available in woven fabric composites. Zhang
et al.21 studied the tensile behaviour of carbon-glass/
epoxy hybrid composites. Gujjala et al.16 studied the
mechanical properties of woven jute–glass hybrid-reinforced epoxy composite. Pothan et al.22 investigated the
tensile and flexural behaviour of woven sisal fabric/
polyester textile composites effect of weaving pattern.
It was found that the matt type of woven composite has
better mechanical properties than plain and twill types
due to resin permeability. Khan et al.23 studied the
mechanical properties of woven jute fabric reinforced
poly(l-lactic acid) composites. It was reported that
woven jute structure exhibited excellent mechanical
behaviour under tensile, flexural, and impact loadings
compared to non-woven composite. This result was
related to the fibre interlocking in weaving structure
that increases the strength of the composites and the
fibres attached together tightly in weaved structure.
Physical and mechanical properties of hybrid composite determine the effectiveness of hybridization. Jawaid
et al.24 studied the mechanical (tensile, flexural, impact)
and physical (hardness, water absorption, and thickness swelling) properties of oil palm empty fruit
bunch/glass hybrid reinforced polyester composites.
The study shows that the hybrid composites exhibited
good properties compared to the EFB/polyester composites. Mechanical property analysis of woven treated/
untreated woven jute and glass fabric was carried out
by Ahmed et al.25 Amico et al.26 investigated the effect
of stacking sequence on mechanical properties of sisal/
glass fibre composites and found that the flexural properties of the hybrid composite increases when sisal fibre
is stacked between glass fibre layers. Khanam et al.15
carried out experiment on the physical properties of
sisal–polypropylene. Properties studied in the work
are tensile, flexural, and chemical resistance of the composite. Saw et al.27 studied the effect of jute fibre
hybridization and different layering pattern on the
physical, mechanical, and thermal properties of jute/
bagasse hybrid fibre-reinforced epoxy novolac composites. They conclude that jute–bagasse hybrid fibre-reinforced epoxy novolac composites could find potential
applications as high-performance engineering materials. Romanzini et al.28 studied the influence of fibre
content on the mechanical and dynamic mechanical
properties of glass/ramie polymer composites.
Ramesh et al.29 studied the mechanical properties of
sisal-jute-glass fibre reinforced polyester composites.
The results indicate that the incorporation of sisaljute fibre improve the properties of the composites.
Generally, researchers studied on kenaf composites
because it is sustainable and is increasingly being
considered as reinforcements for polymer matrix composites.30 The research among others are hybrid kenaf/
glass reinforced epoxy composite for passenger car
bumper beam,18 kenaf glass fibre reinforced polypropylene composites, Kenaf/fibrefrax hybrid phenol-formaldehyde,31 kenaf-glass fibres reinforced unsaturated
polyester hybrid composite,32 kenaf/PALF-reinforced
HDPE composite,33 and rubber toughened polyester/
kenaf composite.34 Limited research involved woven
kenaf for examples in Dan-mallam et al.35 and Hani
et al.36 Even though research on the usage of natural
fibre is widely explored, the usage of natural fibres
kenaf in the woven form has not been studied to a
great extent. In this study, fabrics obtained from
kenaf yarn and commercially available Kevlar-129 has
been used as hybrid composite in epoxy resin. The performance of kenaf-Kevlar hybrid composite and the
effect of fibre weight fraction composites were
evaluated.
Materials and methods
Materials
The woven kenaf fabric was produced by handloom
weaving process using kenaf yarns. The properties of
kenaf yarn and woven fabrics are as tabulated in
Table 1. The chemical composition of fibres used are
cellulose 62.6%; hemicellulose 16.8%; lignin 7.83%;
and ash 1.66%. The aramid fibre used in this study is
Kevlar129, chemical composition of which is poly
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para-phenyleneterephthalamide (PPTA), also known as
para-aramid. The polymerization of poly (p-phenylene
terephthalate) involves the reaction of an aromatic diamine (p-phenylene diamine) and an aromatic diacid
chloride (terephthaloyl chloride in an amide solvent
as shown in Figure 1).37
The properties of Kevlar is as shown in Table 2. The
matrixes are D.E.R.331 liquid epoxy resin with a density of 1.08 g/m3. The resin was cured using joint amine
type (905-3S). Non-silicone mould release agent formula 700-A supplied by Aerosol Specialist Sdn Bhd
used prior to fabrication processes. Figure 2 shows
the fabric used for kenaf-Kevlar hybrid laminated
composite.
Fabrication of hybrid composites
Hand-lay-up method was adopted to fabricate laminates of Kevlar 129 and woven kenaf in epoxy resin.
Woven kenaf and Kevlar fabric were hand lay-up
with the epoxy matrix by mixing epoxy resin (DER
331) and amine hardener in the ratio of 2:1
(Figure 3). Two thick mild steel plates are used as a
mould (20 20 cm2) in the fabrication process. All the
Table 1. Properties of woven kenaf.
Properties
Woven kenaf
Yarn breaking load (N)
Fabric tensile strength (MPa)
Fabric elongation at break (%)
Fabric thickness (mm)
144.3
9.88
15.37
2.878
mould surface was sprayed with a mould release agent
to prevent adhesion of composites to the mould after
curing and also to ensure smooth sample surface. For
each hybrid composites, the volume ratio of matrix of
fibre was kept approximately 70:30. The composites
were prepared by hand lay-up method in laminate configuration. Kevlar/kenaf hybrid composites were fabricated with total fibre content of 30%. The ratios of
Kevlar to kenaf woven were varied to get a range of
hybrid ratio of pure Kevlar to a mixture of Kevlar and
kenaf, to pure kenaf. As shown in Table 3, the ratio
Kevlar/kenaf weight (%) are H1 (78/22), H2 (63/47),
H3 (50/50), H4 (26/74), and H5 (32/68). Composites
were cured by applying compression pressure using
dead weights on the top of the mould and cured at
room temperature for 24 hours. After curing the laminated composites were cut into required size for physical and mechanical characterization.
After fabrication the density hybrid laminates were
measured using the densimeter MD-200 S, Mirage,
Table 2. Properties of Kevlar fabric.38
Properties
Kevlar 129
Fibre diameter (m)
Fibre density (g/cm3)
Tensile strength (GPa)
Tensile modulus (GPa)
Elongation at break (%)
Fabric density (per cm)
Fabric weight (g/m2)
Thickness (mm)
12
1.43
3.4
99
3.3
8.5
190
0.3
Figure 1. Synthesis of PPTA.
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Figure 2. Woven kenaf and Kevlar fabric.
Figure 3. Configuration of composite samples.
Table 3. Composition and designation of the composites.
Weight of fibres, %
Total fibre
Sample
Thickness (mm)
Kevlar
Kenaf
Weight fraction, %
Volume fraction, %
H1
H2
H3
H4
H5
All kenaf
All Kevlar
5.62
9.50
6.28
11.00
7.78
5.13
2.70
78
63
50
26
32
0
100
22
37
50
74
68
100
0
35.2
37.6
34.6
36.6
34.7
39.3
36.2
29.0
31.4
28.7
30.7
28.9
33.4
29.9
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according to the ASTM D792 standards. The void content was determined from the theoretical and the
experimental density of the composites through equations (1) and (2)
tester. Five un-notched samples of dimension
80 mm 10 mm respective thickness from each composition were tested. The energy needed to break the
samples and composite toughness can be analysed.
theorethical experimental
100%
theorethical
ð1Þ
SEM study. In order to study the morphological feature
of the fibre-matrix interface due to mechanical testing
the surfaces of the samples were examined using a scanning electron microscope (SEM; LEO 1430 VPSEM,
Carl Zeiss, Germany).
Void contents ð%Þ ¼
where
theorethical ¼ wf
f
1
þ wmm
ð2Þ
where Wf is the fibre weight fraction, Wm is the matrix
weight fraction, f is the fibre density, and m is the
matrix density.
Experimental procedure
Tensile test. Tensile test was conducted to determine the
stress–strain behaviour of the Kevlar-kenaf hybrid
laminated composite. The test was carried out using
Instron 33R 4484 testing machine based on ASTM D
3039 on plates with a size of 250 mm 25 mm sample
thickness for each composite. The samples were carefully cut from the laminate using wheel saw and finished to the accurate size. A standard head
displacement at a speed of 5 mm/min was applied.
For each sample, three specimens were tested and average results were obtained.
Flexural test. The flexural test was conducted from
3-point loading using Instron 33R 4484 testing machine
according to ASTM D 790. The rectangular samples of
dimension 200 mm 10 mm were cut from the laminates using circular saw. The tests were conducted at a
crosshead displacement rate of 2 mm/min and the span
to depth ratio was 16:1. For each sample, three specimens were tested at room temperature and the average
was taken as a final result.
Results and discussion
Prior to mechanical testing, composite sample was
tested for void content based on theoretical and actual
density. The density and void content of composites are
presented in Table 4. All kenaf and all Kevlar impact
properties are also reported for comparison.
The stress–strain curve of Kevlar/epoxy, kenaf/
epoxy, and hybrid kenaf-Kevlar hybrid composite
were plotted for the determination of ultimate tensile
strength and elastic modulus as shown in Figure 4.
Table 4. Density and void content of the composites.
Samples
Density (g/cm3)
Void content (%)
H1
H2
H3
H4
H5
All Kenaf
All Kevlar
1.13
1.12
1.03
1.01
0.88
1.13
1.14
3.15
4.38
5.02
12.98
25.67
15.62
4.55
Interlaminar shear test. The test was performed following
ASTM 2344 to determine the interlaminar shear
strength of the composites. Samples of 10-mm length
and square cross section are loaded under three-point
bending at the rate of 2 mm/min. The apparent interlaminar shear strength of composites was determined
from ILSS specimens that were tested with a support
span/specimen thickness ratio of 5:1.
Impact test. The test samples are prepared and tested
according to the ASTM D256. The Charpy test was
performed on five samples using a pendulum impact
Figure 4. Stress–strain curves for kenaf/epoxy, Kevlar/epoxy,
and kenaf-Kevlar hybrid composites.
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The strength of woven kenaf used in this study is as
shown in Table 1. The properties of Kevlar fabric were
taken from literature as stated accordingly. Tensile
properties of the woven kenaf/epoxy, Kevlar epoxy,
and Kevlar-kenaf hybrid composites tested are shown
in Figure 5. It was observed from Figure 5 that the
sample H1 showed a higher tensile strength and modulus; 202 MPa and 3.4 GPa, respectively, compared to
other hybrid samples. This is because this sample contained a higher percentage of Kevlar, which are stronger and stiffer than kenaf fibres. Generally, the tensile
strength and modulus of elasticity of composite
decreased as the Kevlar fibre volume fraction decreased
in sample H1 to H3. The tensile strength at break of the
kenaf/epoxy sample scored around 16 MPa. By adding
about 15% w/w of Kevlar as in sample H3, the strength
of the composite increased up to 100 MPa. Additional
more kenaf content in samples H4 and H5 reduced the
tensile properties of the hybrid composites. The
increases in Kevlar content in sample H1 and H2
increased the tensile properties of hybrid composite
up to 202 MPa. Compared to H3, there are 10% and
20% reduction of kenaf content in H2 and H1 which
results in 49% and 100% increase in tensile strength,
respectively. An increase of 10% and 20% of kenaf in
H5 and H4 reduce about 50% of hybrid composite
tensile strength. Similar trend is observed in tensile
modulus.
The tensile strain at break shows that kenaf/epoxy
break at 5.78% strain. The strain values for hybrid
composites increased with the increase in Kevlar content in samples H1 and H2, while the value decreases as
more kenaf fibres are added except in sample H4. The
tensile modulus of composites also improved with
Kevlar fibre volume increase in samples H1 and H2.
Additional kenaf volume fraction in H4 and H5 compared to sample H3 did not improve the tensile properties of hybrid composite. This may be due to the
presence of voids as both the tensile strength and
modulus decreased with increasing void content.39
The effect of kenaf fibre content on tensile strength
of hybrid composites is analysed and are shown in
Figure 6. Tensile properties of composite material are
mainly depending on fibre strength and modulus. The
experimental results clearly indicate the trend of
decrease in tensile strength and tensile modulus as the
volume percentage of kenaf increased. Tensile modulus
determines the ability of samples to resist deformation.
In this case, it shows that samples with kenaf content
less than 14.5% resist more to deformation compared
to the samples with higher kenaf content. The equal
tensile strength and tensile modulus is achieved at the
kenaf content of approximately 14.5%. Thickness of
samples also influenced the tensile properties of composites. The increase in thickness of laminates tends to
decrease the tensile strength. The laminated specimens
with lesser thickness lead to more ultimate tensile
strength irrespective of fibre orientations.34 The tensile
properties of woven kenaf/epoxy composite in this
study are 16.46 MPa and 500.1 MPa, respectively.
Flexural test was conducted to determine the capability of a material to withstand the bending before
reaching the breaking point. The flexural load-extension curves for various hybrid composites, kenaf/epoxy,
Figure 5. Tensile properties of composites.
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Figure 6. The effect of kenaf content on tensile properties of hybrid composites.
Figure 7. Flexural-load extension curves of composites.
and Kevlar/epoxy composites are shown in Figure 7.
All the curves indicate non-linear behaviour with the
highest maximum load in Kevlar/epoxy composite, followed by the hybrid samples. Kenaf/epoxy is the lowest
because of flexural strength and modulus are controlled
by the strength of the extreme layers of composite.23
Figure 8 shows the results of the flexural properties
for the hybrid composite with different volume fraction
of kenaf/Kevlar compared to kenaf/epoxy and Kevlar/
epoxy composites. The results indicated that the kenaf/
epoxy composite recorded the lowest flexural strength
and modulus; 6.64 MPa and 3.27 GPa, respectively.
This figure clearly shows that the Kevlar-epoxy composites were much more rigid, and stronger, than the
kenaf-epoxy. It can be seen that H2 has the highest
flexural strength and modulus compared to other
hybrid composites. This may be the effect of higher
total fibre contents, void content, and fibre-matrix
adhesion strength in the samples. In the sample
tested, the Kevlar layers were put as outer and it
takes more stress compared to woven kenaf. Flexural
strength is a combination of the tensile and compressive
strengths which directly varies with the interlaminar
shear strength, whereas the flexural modulus is a measure of resistance of composites to bending deformation.40 The flexural strength and modulus of the
hybrid composites as a function of kenaf content are
presented in Figure 9. Similar to tensile properties,
compared to samples H3 which consist of an equal
volume percent of Kevlar and kenaf, a reduction of
10% to 20% of kenaf in samples H1 and H2 will
result in the increase in flexural strength and modulus
of about 42% to 88%. As can be seen, the flexural
properties decrease with increased kenaf content. The
flexural strength and modulus shows a higher peak at
the 11.9% and 22.6% kenaf content.
The interlaminar shear strength (ILSS) of Kevlar/
epoxy, kenaf/epoxy, and kenaf-Kevlar hybrid composites was evaluated by using short-beam techniques. The
load-extension curves of the ILSS for various laminate
configurations are presented in Figure 10. Sample
H1exhibit the highest ILSS value of 9.32 MPa.
Figure 11 shows the ILSS of hybrid composites compared to kenaf/epoxy and Kevlar/epoxy composites.
The maximum value of the ILSS for hybrid composites
is in H1 and the lowest in sample H3. Generally, hybrid
composites show higher ILSS compared to kenaf/epoxy
composites except for H3. The all-Kevlar samples have
the second highest ILSS to H1. This may have happened because the samples were thin with a very short
span. The effect of Kevlar and kenaf volume fraction is
shown in Figure 12. The ILSS of the composites
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Figure 8. The flexural properties of the hybrid composite.
Figure 9. The effect of kenaf volume fraction on the flexural properties of the hybrid composite.
increased with the Kevlar fibre incorporation in H1 and
H2 compared to H3. The similar trend occurred in H4
and H5 when the kenaf content increased. It shows that
ILSS is primarily dependent on the matrix properties
and the fibre/matrix interfacial properties rather than
the fibre properties.41 ILSS results from combination
failure modes such as fibre rupture, micro buckling,
and interlaminar shear cracking. The effects of voids
have detrimental effects on the ILSS of composite
laminates. In this study, samples H3, H4, and H5,
which contain a high void fraction, recorded lower
ILSS compared to lower voids samples. The ILSS
may be used to evaluate interface strength and may
also indirectly address fibre/matrix adhesion and void
content.42 ILSS data give information about the fibre-
matrix adhesion. By using a short beam, it is assumed
that the beam is short enough to minimize bending
stresses resulting in interlaminar shear failure by cracking along a horizontal plane between the laminates.
Figure 12 shows the changes in ILSS with kenaf
contents in hybrid composites. It is clearly shown that
ILSS reduced as the volume fraction of kenaf
increased. This is probably due to the poor interaction
between kenaf fibre-epoxy and also void content in the
composites.
Impact test was conducted to analyse the energy
absorption capability of the different samples. The
absorbed impact energy (in Joule) is the total energy
required to fracture the specimen. It is determined from
the difference in potential energy before and after the
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Figure 10. Load extension curves for ILSS of composites.
Figure 11. ILSS of laminated composite.
test. The impact strength (kJ/m2) was calculated by
dividing the recorded absorbed impact energy with
the cross-section area of the samples. Figure 13 presents
the impact properties of kenaf-Kevlar hybrid composites. All kenaf and all Kevlar impact properties are also
reported as a comparison. Results show that for all
types of composites, impact strength improves at different levels as the Kevlar fibre content increases. This
improvement was due to higher amount of highstrength fibres that can transfer the impact stress effectively.43 The impact properties of fibre composites are
highly influenced by many factors, including interfacial
bond strength, the matrix, and fibre.31 The impact failure of a composite occurs by factors such as fibre/
matrix debonding, fibre and/or matrix fracture, and
fibre pull-out. Based on the result, the Charpy impact
properties of samples H1 and H4 was higher with the
values of 34.22 J and 34.86 J, respectively. Sample H1,
as expected, showed better impact properties than H4
and H5 because of Kevlar and void content in the samples. The result indicates that the impact values for H4
and H5 are nearly similar. This may be due to the
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Figure 12. Interlaminar shear strength of composites.
Figure 13. Impact properties of composites.
sample’s thickness, fibre content, and high void content
in samples tested. Impact toughness of samples H1, H4,
and H5 are higher than Kevlar/epoxy composites, may
be due to the effect of kenaf reacts as fillers to reinforce
the epoxy matrix.44 The relationship between kenaf
fibre loading and impact strength of hybrid composites
is shown in Figure 14. Although the impact strength of
the composite shows a large scatter, there is a trend of
decrease of impact strength with increasing kenaf fibre
loading.
The tensile fracture surface of the composite is subjected to SEM examination to understand the fracture
behaviour. Figures 15 and 16 show the SEM micrograph of samples H1 and H4. Figure 14 shows the
presence of voids, fibre pull-out, which indicates poor
fibre-matrix adhesion, which resulted in poor tensile
strength of sample H4. Fracture with less or no fibre
pull out is observed in Figure 16. These observations
indicate the fibre-matrix interface determined the tensile properties of hybrid composites.
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Figure 14. The relationship between kenaf fiber loading and impact strength of hybrid composites.
Conclusions
This study focused on the evaluation of the effect of
fibre loading of Kevlar/kenaf on the mechanical properties of woven hybrid laminated composites. The
mechanical properties of hybrid composites were
found to be affected differently by the Kevlar/kenaf
weight ratios. Overall performance of Kevlar/epoxy is
superior compared to the kenaf/epoxy, which was
expected due to the poor mechanical properties of
kenaf compared to Kevlar. In all, it was shown that
the hybridization affects in intermediate mechanical
properties of composites compared to the highest
Kevlar/epoxy properties and the lowest properties of
kenaf/epoxy composite.
Figure 15. SEM micrograph of sample H1.
Acknowledgements
The authors would like to show their appreciation to
Universiti Putra Malaysia and Science and Technology
Research Institute for Defence (STRIDE) for supporting
the research activity.
Conflict of interest
None declared.
Funding
This work was supported by the Ministry of Education
Malaysia under the Research Acculturation Collaborative
Effort (RACE) Grant Scheme (Project number: RACE/F1/
TK2/UPNM/10).
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