A Study on Properties of Natural Fibres - A Review

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 10 | Oct -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1343
A STUDY ON PROPERTIES OF NATURAL FIBRES - A Review
K. Arun Kumar1 , S. Madhu Sudhanan2, K. Mahesh Kumar3, G. Ranjith Kumar4
1Assistant Professor, Mechanical Engineering, Sri Ramakrishna Engineering College, Coimbatore
2,3,4 Students, Department of Mechanical Engineering, Sri Ramakrishna Engineering college, Coimbatore
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Abstract - Growing towards the eco-friendly technology
natural fibres takes main part in the field. This study is
about discussing the properties of natural fibre and
natural fibre composites. Influence of various factors like
fibre diameter, fibre content, density, fibre size, geometry
of fibre and coupling agents towards the mechanical
properties, thermal properties and water intake properties
are presented in this study. Improvement on Surface
treatment and addition of coupling agents can improve
the property which is low. These techniques improve the
mechanical properties, thermal properties and water
absorption properties.
1. INTRODUCTION:
Over the last decades, natural fibres received
increasing attention as alternative to synthetic fibres
both from academic world and various industries. There
is a variety of different natural fibres, which can be used
as reinforcements of polymer (i.e. thermosets and
thermoplastics) composites. Four main reasons make the
natural fibres more attractive than others: i.e. specific
properties, price, biodegradability and recyclability.
Particularly, high specific and low density properties are
nice benefits. Other than this, they are renewable and
have a CO2 neutral life cycle, compare to their synthetic
competitors (i.e. carbon and glass) [1, 2].
Driven by the introduction of regulatory norms
demanding more environmental-friendly products, the
use of natural fibres as reinforcements for composites
materials has increased significantly in the last decade
[3]. Natural fibres such as flax, jute, hemp and kenaf offer
low carbon footprint and biodegradability advantages
combined with a high specific strength and stiffness at a
low-cost [4-6]. The application of natural fibres is
motivated by a combination of environmental
sustainability, cost-effectiveness, recycling and
biodegradation properties [7]. Natural fibres are used as
reinforcement in structural applications in automotive
industry. Natural fibres such as hemp and flax are used
to manufacture door panels and the roofs of cars [8].
Fibre reinforced polymer composite materials have
played an important role in a variety of applications. As a
result of the increasing environmental awareness, the
concern for environmental sustainability and the
growing global waste problem is increased year by year.
Fibre-built polymer matrix composites are finding
applications in households and industries because they
have more favourable properties such as high stiffness,
greater strength, better fatigue performance, more
corrosion resistance, low thermal expansion, low energy
consumption during manufacturing and have non-
magnetic properties. Epoxy resin and its composites
have received considerable attention over the years for
their use as structural materials at low temperature.
2. TYPES OF PLANT BASED NATURAL FIBRES:
2.1. Bast fibre
Bast fibres are usually extracted from the outer bark
of plant stems. Some examples of bast fibres are jute
(Corchorus olitorius/ Corchorus capsularis), flax (Linum
usitatissimum), abaca (Musa textilis), and kenaf
(Hibiscus cannabinus). Retting is the process through
which these bast fibres are extracted, and is
accomplished through biological or chemical
degradation of cut plant stems.
2.2 Leaf fibre
Leaf fibres are coarse and hard fibres obtained from leaf
tissues by hand scraping after beating/retting process or
mechanical extraction. Owing to the relatively high
strength, leaf fibres are typically used for the production
of ropes, fabrics, carpets and mats. Examples of leaf
fibres are sisal, caroa, henequen and pineapple.
2.3. Seed fibre
Coir fibre is a typical example of seed fibre, and it is
extracted from the coconut husk. These lightweight and
strong fibres are mainly used in the production of ropes,
mats, sacks, brush, geotextile and etc. Another set of seed
fibres are also extracted from the pod or boll of some
plant seeds. Examples are cotton and kapok.
2.4. Stalk fibre
These are fibres from plant stalks, and are typically
extracted from plants such as sugarcane, corn, eggplant,
sunflower, wood and the straw of various grain crops

such as barley, wheat, rice and etc. Pulp from some of
these fibres has been utilized in paper and paperboard
products.
2.5. Grass and other fibre crop residue
Widely available tall grasses such as ryegrass (Lolium
perenne), elephant grass (Pennisetum purpureum),
switchgrass (Panicum virgatum) and bamboo (Bambusa
vulgaris) are important sources of fibres. Fibrous crop
residues such as pulse seed coat, peanut shell, hazelnut
husk, corn husk, millet stover, and etc. can potentially be
used as fibre reinforcements in cement-based
composites.
2.6. Wood and specialty fibres
Wood fibres are sourced from a wide variety of trees.
Hence, they are in abundant supply across the world.
Wood fibres are broadly divided into two groups,
softwood and hardwood. The major difference between
these two groups is that while softwood fibres are
generally longer than hardwood fibres [9].
3. NATURAL FIBRE’S PROPERTIES:
3.1 MECHANICAL PROPERTIES:
The kenaf, jute, and hemp yarns that were to
produce the woven fabrics were prepared. The
EpoxAmite 100 series resin was selected as the polymer
matrix, and it was mixed with a hardener in a ratio of 3:1
to form the binder for the composite preparation. For
tensile testing, dog bone specimen used using a Dremel
4000 tool and it was performed using a 100 kN universal
testing machine. Results (Fig 1) indicate that the
incorporation of a high strength kenaf fibre with the jute
and hemp fibres enhanced the ability of the interwoven
hybrid composites to resist breaks and deformation
under a tensile load, in comparison with the individually
woven composites [10].
Sisal plants were prepared. Some portions of cleaned
fibres were soaked in 10 wt% NaHCO3 solution for 24 h,
120 h and 240 h at room temperature, then washed with
distilled water and dried in an oven at 40C for 24 h.
Tensile test was conducted in UTM . It is possible to
observe that the values of both Young's modulus and
tensile strength increase with increasing the treatment
time up to 120 h. After 120 h of treatment, Young's
modulus keeps increasing whereas tensile strength of
the treated fibres begun to decrease. This may be due to
degradation phenomena which occur if the treatment
time is too long [11].
Fig1-Tensile properties of various woven composites in
dry and saturated condition
Agricultural fibres retrieved after the crops
harvesting called agro fibres. Agro-fibres are bonded
with bioplastics called Agro-Plastics. Prototypes are
made for TRAshell, Plant Culture. It is bonded with a bio-
based epoxy resin through a closed molding process.
Plant culture is composed of agro-fibres compounded by
a bio-based thermoplastic matrix (PLA bioplastic). Test
was conducted on Uni-axis tensile test with the same
specimen size. The E-Modulus and tensile strength
properties are described in the Fig 2. From the figures, it
is clear that Plant Culture has shown the highest
performance in comparison to others [12].
Two natural fibres extracted from fruit (borassus) and
bast (ramie) were mechanically characterized. A
commercial grade of PCL (Capa 6500) used as matrix.
Fibres were treated in a sodium hydroxide solution
(5%w) for 4 h at room temperature. 10, 20 and 30 wt%
amounts of natural fibres were tested on a Zwick/Roell
Z010 equipped with a 200 N load cell. Results reported
that the addition of ramie fibres results in a significant
increase in both tensile strength and Young’s modulus of
the composites compared to the neat matrix. A slightly
different behaviour is presented by borassus fibres that
did not cause an improvement of the strength over that
of neat PCL (Fig 3) [13].

Fig 2- Comparison of Composite Materials- Ultimate
strength and Elastic modulus
Fully bio-based thermoplastic composites are
manufactured with bio-based polyethylene(85%) (From
sugarcane) and short fibre coming from Cortaderia
selloana (CS) wastes. Fibres were in the 1-4mm range.
Cortaderia selloana fibers treated in a 15 wt% NaOH
solution. Tensile and flexural properties of the different
samples of bio- HDPE/CS were measured with a
universal test machine with a load cell of 5 kN. From
results (Fig 4) the fibre content increases, both the
tensile and flexural modulus increase [14].
Epoxy matrix was mixed with a mechanical stirrer with
2.5, 5, 10 wt% of basalt powder respectively to the total
weight. The compositions were mixed with curing agent
Z1[tri ethylene tetramine]. The epoxy composites were
fabricated in a mold using hand layup method. Tensile
mechanical properties were measured with INSTRON
4481 universal testing machine with a load cell of 50 kN.
In all cases from results found that basalt filler
introduction led to an increase of the elasticity modulus
of the composites and a reduction of their elongation at
break. Introduction of higher amounts of the powder
may cause formation of (defects) in epoxy matrix [15].
Fig 3 - Tensile strength for composites reinforced
with borassus and ramie fibres
Fig-4 Mechanical properties of bio-HDPE/CS composites
in terms of the wt% of Cortaderia
Cement masonry blocks reinforced with
lechuguilla natural fibres, that were lightened with
polyethylene terephthalate. A concrete mix was designed
for a target compressive strength of 16 MPa at 28 days.
Masonry concrete blocks were produced for two
different fiber lengths (25 and 50 mm) and with fiber
contents of 0.25%, 0.50%, 0.75% and 1.0%. Based on the
obtained results, it was found that as the aspect ratio
decreases the compressive strength increases [16].
Natural Hemp Fibres are taken. The short length hemp
fibers treated with 5% NaOH (THF) were sandwiched in
bisphenol A-aniline based benzoxazine (BA-a) to form
the resin-fibre-resin composite. It was detected that with
increase of fiber content from 0 to 25 volume % Tensile
strength gradually increases. Addition of 25 vol % THF

doubles the Tensile Strength of composite as compared
to poly(BA-a) (Fig 6) [17].
Fig-5 Mechanical properties of composites
Fig-6 Stress strain for THF content
Basalt fiber (BF) was used to reinforce polylactide
(PLA) to obtain new composites with potential structural
or engineering applications. The tensile strength and
modulus increase with increasing BF loadings. 20 wt%
BF can increase the strength and modulus by about 30%
and 47% respectively (Fig 7) [18].
Composites with different volume fractions (30, 40
and 50 volume %) were confectioned by laying the fibres
in a steel mold and pouring liquid resin epoxy under
pressure of 3 MPa. The specimens were dried for 24 h at
room temperature and then tested in an universal
Instron tensile testing machine. From results the
presence of eucalyptus fibres did not affect the tensile
strength but increased the elastic modulus of epoxy
matrix composites. Indeed, the value of elastic modulus
increased approximately 50% for epoxy matrix
composites [19].
Sisal Fibres are taken to study the effect of the
alkalinity of pore solution on fibre degradation
metakaolin (MK) with 10 wt% (MK10) and 30 wt%
(MK30). The specimens were demolded after 24 h and
immersed in pH-saturated water at 23±2 °C for 28 days
prior to accelerated aging treatment. Stress–strain
curves obtained by uni-axial tensile testing of selected
sisal fibres. It can be seen that the tensile strength of the
embedded fiber in MK30 after 5 wetting and drying
cycles is slightly higher than that of a raw fiber. It is
caused by the removal of non-cellulosic materials and
impurities [20].
Fig-7 Stress Strain curve for PLA & PLABF
Fig-8 Stress–strain curve of tensile test on sisal fibres
Sisal fibres are prepared. Sisal fibres are treated by
Hornification, Alkali treatment, Polymer impregnation,
Hybrid treatment. The tensile tests were performed in an
electromechanical testing machine with a load cell of 1
kN. For alkali treatments the tensile strength of sisal
fiber was improved by 32%. Reason of the increment in
the tensile strength and elongation is the removal of non-
cellulosic materials and impurities. The treatment with
polymer and hybrid increased 50 % and 60 % tensile
strength (Fig 9) [21].
Natural fibre composite plates are made from hemp,
flax and jute fibres are subjected to pure compression.

Epoxy resin is used for composition. The buckling and
post-buckling responses are stable and the final
condition is reached in a predictable and stable manner
.From Fig 10 Jute have high tensile strength and Flax
have high elastic modulus. From results this natural fibre
composite sections can be used in light structural
applications such as in the residential and light
commercial markets [22].
Fig-9Influence of fibre treatments on the sisal fibre
tensile behaviour
Fig-10Stress Strain Curve for Fibre composites
Short fibres (1-4mm) from Cortaderia selloana (CS)
wastes are collected. These fibres are treated with bio-
based polyethylene compounds like maleic anhydride,
hydrophobic silane, Sodium hydroxide and alkali
treatment. Mechanical properties evaluated by impact
and tensile tests. Addition of fibre (30%weight)
increases the stiffness while Tensile strength not
affected but gradually increased. But elastic modulus
increased twice for 15-20% fibre content (Fig 11) [23].
Coir fibres are taken for alkali treatment. These
coir fibres are reinforced with epoxy [CFRE]. Then CFRE
treated with 5% weight NaOH solution for 30 min at 20
C. Mechanical properties of CFRE were determined by
tensile test on the Instron 5567 machine. Alkali
treatment improved the tensile and flexural properties.
From results found that 16.7% and 17.8% growth in
flexural and tensile strength respectively [24].
Coir fibres are taken from husk as hydrated and
dehydrated form. Tensile test was carried out on
horizontal environmental micromechanical tester (max
450g). From results (Fig 12) that dry fibres have higher
strength than the wet fibres. Fibre diameter is larger in
Wet specimen [25].
Fig -11 Tensile Properties
Fig-12 Stress Strain Curve for Dry (a) and Wet (b)
Specimen
From herbaceous plants [family-musaceae] banana
fibre is obtained. Flax fibre is obtained from family
linaceae. Epoxy and Hardener is used in the ratio of 9:1.
Fabrication process is made by sandwich method. By
hand layup method one layer of banana fibre is
sandwiched between two flax fibre layers. The result
(Fig 13) shows that hybrid composite has better
properties than other single fibre glass reinforced
composites under flexural and impact test. It is found

that the hybrid composite have high strength than the
single fibre composites [26].
Fig-13 Comparison of Break Load, Maximum Deflection
Banana fibres are obtained from plant. Polypropylene
(PP) and maleic anhydride grafted polypropylene
(MAPP) are mixed in the weight ratio of 95% and 5%
respectively. Composites are prepared in the ratio of
70:30 for PP and fibre respectively. Tensile test was
conducted on Universal Testing Machine (5kN) for five
specimens at temperature of 25°C. From results (Fig 14)
that PP/Banana yarn composite have the highest
improvement on tensile strength, which is 294% from
others [27].
Fig-14 Bar chart of Tensile strength
3.2 THERMAL PROPERTIES:
Thermal insulated materials based on natural fibres
are currently high on construction market. Hemp-based
insulated materials are taken. These samples should not
contain more than 20% of weight content. Specimen
made by bi-component bonding method (air-lay) with
the addition of 15% of polyester bi-component fibres.
From result (Fig 15) it is found that Increase in Density
will decreases the Thermal Conductivity [28].
Fig-15 Graph plotted between Thermal conductivity and
density
Coir fibres are prepared and washed in water. Then it
kept in 1.6 mol/L NaOH solution for 48 Hours.
Polypropylene(PP) is used as reagent with a density of
0.9 g/cm3. Using thermo gravimetric analysis(TGA)
thermal stability was evaluated. From results show that
the alkali treatment enhances the thermal stability of the
fibres from 324/449°C to 331/474°C,by elimination of
non-cellulosic compounds on the fibres surface(Fig 16)
[29].
Fig-16 TGA of treated and untreated coir fibres
3.3 WATER INTAKE PROPERTIES:
Jute Fibre is selected for this process. Initially fibre is
treated with 18% NaOH to increase mechanical
properties. Epoxy resin is used by hand layup technique
using compression moulding machine. Specimens are
immersed in distilled water. It is carried out 28 days.
From results NaOH treated fibre takes less moisture
content [30].
Ijuk fibres are prepared and cut about 2mm. Then
washed in water and dried in oven for 24 hours at 65°C.
Then fibres are silane treated with Vinyltrimethoxy
silane. Composite fabrication is done using roll mill
mixer. Intake proportions are found from final and initial
weights after and before immersion in water for 24 h.
From results (Fig 17) it was found that Water absorption

increases at higher fibre content and also there was less
difference in treated and untreated fibre [31].
Fig-17 Water absorption for Fibre composites
4. CONCLUSIONS:
Natural fibres and natural fibre composites can be
used in engineering applications because of their
environmental suitability and Economic. Now a days lot
of new composites are generated and technical and
economical issues are noticed. Natural fibre/ Natural
fibre reinforced epoxy composites with high durability
and effective mechanical properties were developed in
the last decade. The main challenges for the near future
are to further improve the durability and the mechanical
performance of these composites by decreasing the costs
of fabrication while developing an eco-friendly strategy.
Blending of fibres is also a better option for
improvement the mechanical and thermal stability of the
natural fibre reinforced epoxy composites. Various
treatments, various resin and various coupling agents
are used to increase the mechanical properties among
these alkali treatment and epoxy resin is widely used
and economically successful.
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