Mechanical
and water absorption behavior of continuous untreated and alkali treated Areca
palm leaf stalk fiber reinforced polymer composites.

 

1 N.Shanmugasundaram,² I.Rajendran, 3M. Jayaraj and  4I. Aravindhaguru

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1,2 Department of Mechanical Engineering, Dr.Mahalingam College of
Engineering and Technology, Pollachi-642003, Tamilnadu, India

 

3,4 Department of
Mechanical Engineering, PA College of Engineering and Technology,
Pollachi-642002, Tamilnadu, India

 

ABSTRACT

 

 

 

 

 

The continuous untreated and alkali
treated areca palm leaf stalk fiber reinforced polymer composites were
fabricated by compression mould technique. The composites were evaluated based
on mechanical properties such as tensile, flexural, impact and water absorption
behavior. The weight fraction of the fiber and matrix was fixed as 30:70 in the
composite. The mechanical property result shows that the alkali treated
continuous areca palm leaf stalk fiber composites gave good result compared to
raw continuous areca palm leaf stalk fiber composites. The fracture behavior of
raw and alkali treated areca palm leaf stalk fiber composites were analyzed by
scanning electron microscope (SEM).

 

 

 

 

 

 

Key words : Areca palm leaf stalk fiber,
Mechanical properties, Weight fraction, Scanning Electron Microscope

 

 

Introduction
 
   Eco friendly fiber composite materials are
one such competent material which replaces the usual and synthetic materials
for the light load applications where we require less weight and energy
conservation. The Global market is promptly moving towards the energy
conservation and energy reduction process. Generally the natural fibers were
frequently used to reduce the weight of the components i.e. the fibers are
reinforced with the suitable matrix. In the aspect of cost, renewable and
biodegradability, the natural plant fibers have plenty of advantages when
compare to the synthetic fibers. Several authors carried out their research in
the area of natural fibers (SathishkumarT.P, Navaneethakrishnan.P et al.2012). Investigate
the various of mechanical properties of tensile and flexural properties of randomly
distributed unsaturated

polyester resin
with sisal/carbon fibre reinforced hybrid composites with different weight
ratio fiber and compared with various natural fiber(P.Noorunnisa Khanam et
al.2010). Analysed the mechanical properties such as tensile, compressive,
flexural, impact strength and water absorption of the alkali treated
continuous Agave fibre reinforced epoxy composite (TCEC) and untreated
continuous Agave fibre reinforced epoxy composite (UTCEC) (K.Mylsamy et.al 2011). studied the effect of surface
modifications on sisal fiber properties as well as on fiber/poly (lactic
acid) (PLA) interface adhesion. (A. Orue et.al 2015)  The compared  mechanical properties were such as  tensile, flexural, and impact strengths of
roselle and sisal fibers hybrid polyester composite at dried up and wet
conditions were studied When length of the fiber

 

 

 

 

 

 

*Corresponding author: E-mail: [email protected]

2

were increased, the tensile and
flexural strength of the composite improved (Athijayamania A,
Thiruchitrambalamb M et. al 2009). Examine the manipulate of fibre morphology
of varous natural fibres on the composites physical and mechanical properties
and on the fibre breakage due to extrusion process(Kristiina Oksman et.al 2009).
Effect of properties due to
the  weaving patterns and random
orientatation on the properties of banana, kenaf and banana/kenaf
fiber-reinforced hybrid polyester composites.  The maximum increase in
mechanical strength was observed in the plain woven hybrid composites rather
than in randomly oriented composites(Alavudeen
et.al 2015). Studied the static and dynamic mechanical properties of alkali
treated continuous Palmyra Palm Leaf Stalk Fiber (PPLSF) and jute fibers
reinforced  hybrid polyester composites. Increasing jute fiber loading
showed a considerable increase in tensile and flexural properties of the hybrid
composites as compared to treated PPLSF composites(D. Shanmugam et.al 2013).
Studies on the behavior of pineapple leaf fibers treated with NaOH and modified
with two different functionalities were attempted by (Threepopnatkul et. al 2009).
Based on the above literature survey the fibers were treated with 5%NaOH
solution and the effects on mechanical and water absorption behavior  of treated continuous Areca palm leaf stalk
fiber composites were studied and the results are compared with raw continuous
Areca palm leaf stalk fiber composites.

 

Methods and Materials

 

Polyester Resin

 

The isopthallic unsaturated polyester
resin is used as a matrix to fabricate the composites. The curing agent’s
accelerator (Methyl Ethyl Ketone Peroxide) and the catalyst (Cobalt
Naphthalene) are used to cure the resin. The chemicals were procured form Covai
Seenu and Company, Coimbatore, India. The mechanical properties of isophthallic
resin are very high and water absorption property was very low compare to other
resin.

 

Extraction of fiber

 

The Areca palm leaf stalk fibers were
extracted from Areca palm leaf stalks. The required quantities of stalks were
collected and leaves were removed and dried at the sunlight for a week. After a
week the stalks were trimmed into separate pieces and immersed in the water

 

 

for four weeks and the fibers were
extracted by mechanical retting process.

 

Alkali treatment of fiber

 

The continuously untreated areca palm
leaf stalk fibers were immersed with 5% sodium hydroxide (NaOH) solution for
30min.The fibers were washed with flow water and then washed with very dilute
hydrochloric acid (HCI) continuously till the fibers were free from alkali.
Then the continuously treated areca palm leaf stalk fibers were dried at room
temperature for 2 to 3 days.

 

Fabrication of composites

 

The rectangular mild steel plate of
200x 150x10mm3 was used to fabricate the composites. The mould was assembled
with top and bottom plate. The continuous fibers were longitudinally
distributed inside the bottom plate and cover with top plate to compress the
mould for 15mintues to produce a fiber mat of 5mm thickness. The mat was taken
away from the mould and kept separate. Then the mould was cleaned and releasing
agent was applied on the mould to easy removal of composite after curing. The
matrix was prepared with adding of accelerator and catalyst in isophthallic
resin to stir continuously to ensure homogeneity. The fiber mat is placed again
in the bottom plate and the matrix was poured in the bottom die and top plate
is used to cover the bottom plate. The uniform pressure of 1ton was applied for
12 hours continuously to top and bottom plate to compress the composite. After
that the composite plate was taken away from the mould and cut into ASTM
standard size for different tests. The continuous untreated areca palm leaf
stalk fiber composites were named as UAFC for treated areca palm leaf stalk
fiber composites were named as TAFC.

 

Tensile test

 

The tensile tests of the composites
were determined according to ASTM D 638-Type I. Initially the tensile specimens
were cut from the fabricated composite plate. The test was conducted using
Instron tensile testing machine with crosshead speed of 5mm/min with gauge
length of 57mm. Five specimens were tested and average values were showed. 

 

Flexural test

 

 

The three point
bending tests of the composites were conducted according to ASTM D 790. The
size of 127 X12.7 X5mm3 was cut from the fabricated composite

 

plate. The Lloyd instrument LR with
100 KN was used to conduct the flexural strength with cross head speed of
1mm/min. Five specimens were tested and average values were calculated.

 

Impact test

 

The Izod impact
tester was used to conducted impact tests according to ASTM D 256. The size of
64X13X5mm3 was cut from fabricated composite plate. Five specimens were tested
and average values were reported.

 

Water absorption test

 

The specimens were
cut from the fabricated composite plates according to the ASTM D 570-98. The
size of the specimen was 76.2X25.4X5 mm3 used to conduct the tests. Initially
the dry specimen’s weight was noted using electronic balancing machine with
accuracy of 0.00001mg. The specimens were immersed in the distilled water and
removed from the water at regular interval of time. Then the specimens were
cleaned using issue paper to remove the excess water present on the specimen
surface and the measure the weight of the samples. The initial weight of the
dry sample to final weight of wet sample provides the percentage of water
absorbed by the composite.  

 

Scanning electron microscopy

 

The scanning
electron microscopy(SEM) model JEOL 6390 at accelerating voltage of 10 kV were
used to analyze the fracture behavior of 
continuous areca palm leaf stalk untreated and treated fiber composites
surfaces.

 

Results and discussions

 

Tensile properties

 

       The effects of alkali treatment on
tensile properties of continuous areca palm leaf stalk fiber reinforced
composites were explored. The TAFC shows better improvement in tensile strength
and tensile modulus compared to UAFC. The UAFC showed 15% increased in tensile
strength compared to neat resin. The tensile stress vs tensile curves showed (Figure
1) that the load increases to certain limit the UAFC failed due to poor bonding
between fiber and matrix. (D. Shanmugam et. al 2012).  

 

The TAFC showed
(Figure 2) around 38% and 55% improvement in tensile strength and tensile
modulus (Figure 3) compared to matrix and UAFC.

 

 
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Fig 1.Tensile stress vs tensile
strain for UAFC and TAFC

 

 

 

 

 

 

 

 

 

 

 

Fig 2.Tensile strength of UAFC and
TAFC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 3.Tensile strength
of UAFC and TAFC

 

Flexural properties

 

The
flexural strength and flexural modulus of UAFC and TAFC were shown in Figure 4
and 5. The TAFC were increased 28% and 11% of flexural strength compared to
matrix and UAFC.

4

 

 

It is interesting to observe that
the chemical bonding between the fiber and the matrix in the TAFC showed more
strength because of more shrinkage and toughness inbuilt in the composites. The
flexural modulus increased by 51% and 34% than matrix and TAFC.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 4.Flexural strength
of UAFC and TAFC 

 

This indicates that the fiber
orientation in the longitudinal direction increase the areas of contact between
fiber and matrix and improves the adhesion (Nam TH et. al 2011)

 

 

 

The impact properties of the
composites were highly correlated to adhesion strength between matrix and
reinforcement, the properties of matrix and reinforcement (Sreenivasan VS,
Ravindran D et. al 2012) The TAFC had 67% and 43% increase in impact energy
absorbed for failure which corresponds to 58% and 32% increase in impact
strength compared to matrix.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 6.Impact energy of
UAFC and TAFC

 
In the case TAFC, better interlocking
among the fiber and matrix has allowed for more energy absorption and to
stop the propagation of crack resulting in a notable improvement in impact
properties (impact strength and impact energy) compared to matrix and UAFC.
 
Water absorption properties
 
The natural fibers as
reinforcement in polymer matrix is more sensitive to water which will cause
the poor dimensional stability (Dhakal HN et. al 2001) and will
reduce the mechanical properties of the composite. Figure 8 shows the
function of water 
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 7.Impact Strength
of UAFC and TAFC

 

 

 

 

 

 

 

 

 

 

 

Fig 5. Flexural Modulus
of UAFC and TAFC

 

Impact properties

 

The surface
modification of the fiber influence the impact energy and impact strength of
the composites is shown in Figure 6 and Figure 7.

 

absorption
properties of UAFC and TAFC. The results were recorded for every 30min interval
and results shows that TAFC absorb less water compared to UAFC.

 

 

 

 

 

 

 

 

 

 

 

Fig 8.Water absorption
of UAFC and TAFC

 

The UAFC uptake
more water due to the high amount of hemicellouse, lignin and other impurities
present in the fiber. The alkali treatment removes the hemicellouse, lignin and
other impurities and leading to good mechanical bonding between fiber and matrix.
The water absorption in the composites was found to be 8%, 5% for UAFC after
180min.

 

Conclusions

 

The influence of
alkai treatments on mechanical and water absorption behaviour of continuous
areca palm leaf stalk fiber composites were experimentally determined and the
following conclusions are arrived.

 

The alkali treated
continuous areca palm leaf stalk fiber  
composites (TAFC) had an increased by 38% in tensile strength and
tensile modulus increased by 55% respectively, compared to untreated continuous
areca palm leaf stalk fiber composites (UAFC) due to better load transfer
between the fibers and matrix.

 

The alkali treated
continuous areca palm leaf stalk fiber composites (TAFC) had better flexural
and impact properties compared to untreated continuous areca palm leaf stalk
fiber composites (UAFC) which was due to better interfacial adhesion between
the fibers and matrix.

 

The alkali treated
continuous areca palm leaf stalk fiber composites (TAFC) have decreased the
amount of water absorption compared to untreated continuous areca palm leaf
stalk fiber composites (UAFC).

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