Experimental investigation and analysis of mechanical properties of injection

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME
197
EXPERIMENTAL INVESTIGATION AND ANALYSIS OF MECHANICAL
PROPERTIES OF INJECTION MOLDED JUTE AND GLASS FIBERS
REINFORCED HYBRID POLYPROPYLENE COMPOSITES
Ravishankar. R1
, Dr.K. Chandrashekara2
, Rudramurthy3
1
Dept. of Mechanical Engineering, Sri Jayachamarajendra College of Engg, Mysore, Karnataka
State, India, Pin: 570006
2
Dept. of Mechanical Engineering, Sri Jayachamarajendra College of Engg, Mysore,
Karnataka State, India, Pin: 570006
3
Dept. of Mechanical Engineering, Sri Jayachamarajendra College of Engg, Mysore,
Karnataka State, India, Pin: 570006
ABSTRACT
Preliminary studies were conducted on jute fiber reinforced polypropylene (PP) composites
to ascertain the optimum weight percent of fiber which could give maximum values for the
mechanical properties. It was found to be 40wt%. In the present investigations, effect of reinforcing
glass fibers in the optimized jute fiber reinforced PP composite is studied. The properties such as
tensile, flexural, impact and hardness with respect to randomly oriented jute and glass fiber
variations in the pp matrix are considered. Jute and glass fibers reinforced matrix composites with
different fiber contents were prepared by injection molding. Matrix content is kept as 60wt%. The
variations in jute and glass fibers by weight percentage are 40:00, 35:05, 30:10, 25:15 and 20:20. It
was found that tensile, flexural, impact and Shore-D hardness properties increased with increase in
glass fiber content. Results and discussions are made with the help of experimental data and SEM
micrographs and conclusions are presented.
Key words: Jute fiber, Glass fiber, Polypropylene, Tensile, Flexural, Impact.
1. INTRODUCTION
Fiber reinforced composites are in use in a variety of applications like, automotive interiors,
furniture, aircraft etc. Abundant use of composites in these sectors has been facilitated by
introduction of newer materials, improvement in manufacturing processes and testing methods.
Fiber-reinforced materials have higher mechanical properties and their strength-to-weight ratios are
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
AND TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 4, Issue 4, July - August (2013), pp. 197-206
© IAEME: www.iaeme.com/ijmet.asp
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superior when compared with metals and their alloys. Further, fiber reinforced plastic composite
offer other advantages like non-corrosiveness, translucency, good bonding properties, and ease of
repair. Natural fibers play an important role in developing high performing fully biodegradable
‘green’ composites which could solve environmental problems. Many researchers are of the opinion
that, these fibers offer many attractive technological and environmental qualities when used as
reinforcements in polymer composites [1-7]. Natural fibers are largely divided into two categories
depending on their origin one being plant based and the other animal based. In general, plant based
fibers like jute, coir, sisal, cotton etc are lignocellulose in nature composed of cellulose,
hemicellulose and lignin. Animal based fibers like silk and wool are composed of proteins. Also
natural fibers are low cost, abundantly available, renewable and have high specific properties.
Further, they are less abrasive to machines used to fabricate them. The mechanical properties of
natural fiber composites are much lower than those of the synthetic fiber composites and they are
hydrophobic. Synthetic fibers have very good mechanical properties, moisture repellency, but these
are difficult to recycle. To take advantage of both natural and synthetic fibers, they can be combined
in the same matrix to produce hybrid composites that take full advantage of the best properties of the
constituents [8-15]. With respect to the above considerations, in the present study, investigations are
made to evaluate the mechanical properties of the jute and glass reinforced PP matrix hybrid
composite.
2. MATERIALS AND METHODS
2.1. Materials
Thermoplastic polymer PP, used as matrix material is in the form of homopolymer pellets
supplied by Hindustan polymers, Bangalore, India. It has specific gravity of 0.90–0.91, melting
temperatures of 165–1710
C and crystallinity of 82%. White jute fiber (Corchorus capsularis) used as
reinforcing fiber was obtained from Jute Pragna Suppliers, Bangalore, India. E-Glass fibers used as
reinforcing fibers was obtained from Concord Fiber Glass industries, Bangalore, India.
2.2. Fabrication of composites and test specimens
Jute and glass fibers in the weight percent ratios of 40:00, 35:05, 30:10, 25:15 and 20:20,
were initially mixed thoroughly with PP granules. The mixtures were passed through single screw
extruder at a constant temperature of 1650
C. The extruded composites were cut into pellets using
rotary cutting pellet making machine. The test specimens were prepared from the compounded
pellets using injection molding machine as per ASTM standards.
2.3. Mechanical testing
Tensile, Flexural, Izod impact and Hardness tests were conducted. For each test and type of
composite, 4 specimens were used and the average values are presented.
2.3.1. Tensile test
Tensile tests were conducted according to ASTM D 638 using a Universal Testing Machine
(Make: Hounsfield, UK, Model: H 50 KM, Capacity: 50 KN, Jaw separation speed: 1 to 500
mm/min). The dimension of the dog bone shaped specimen was 175 mm x10 mm x 3.2 mm. Gauge
length was 50 mm.
2.3.2. Flexural test
Three-point static flexural tests were carried out according to ASTM D 790 using the same
testing machine mentioned above. The dimension of the specimens used was 125 mm x12.5 mm x
3.2 mm. Span length was 100 mm.

199
The flexural strength (1) and modulus (2) were calculated using the following equations:
Flexural strength =3PL/2bd2
(1)
Flexural modulus; E =L3
m/4bd3
(2)
Where P is the maximum applied load, L is the length of support span, m is the slope of the tangent,
b and d are the width and thickness of the specimen respectively.
2.3.3. Izod impact test
Izod impact tests were conducted on un notched composite specimens according to ASTM D256,
using pendulum impact tester (Range: 0 to 1.5 Joules). The dimension of the specimen was 65 mm x
12.5 mm x 3.2mm.
2.3.4. Shore-D hardness
Shore-D hardness tests were conducted on specimens according to ASTM D2240 using
Durometer. (Make: Techno Instrument Company, Model: SHR – Mark III, Range: 0 to 100)
2.3.5. Scanning Electron Microscopy (SEM)
Interfacial bonding, dilation of matrix, fiber pulling or fracture between the fiber and PP matrix in
the composites were examined and analyzed using Scanning Electron Microscope. The micrographs
were taken at the magnification of 500.
3. RESULTS AND DISCUSSION
3.1. Tensile properties
Variation in tensile strength with respect to addition of varying percentage by weight of glass
fiber to jute-PP composite is illustrated in the Fig.1. It could be seen that, tensile strength is
increasing with increase in percentage of glass fibers in the composite. Increase in tensile strength is
almost linear with addition of glass fiber with increment in fiber loading in steps of 5wt% up to
20wt%. Percentage increase in strength is found to be 28.67 for glass fiber loading of 20wt%. For
hybridization, addition of glass fiber with natural fiber reinforced composites, the tensile strength
increased with glass fiber loading which is in accordance with the results obtained by other
researchers [8, 9, 10, 11, 12, 13]. Reason is that, glass fiber adherence to the matrix is better when
compared to jute fiber and the interfaces between the fiber and the matrix is more (surface area of
contact). Hence, it is difficult for the prevailing forces to pull glass fibers from the matrix compared
to that of jute fiber. Also the failure of the specimen is mainly due to the fracture of the glass fiber
compared to jute fibers for which pull out of them is the main reason. The range of the tensile
strength found in the current work is 22.18–28.54 MPa.
Fig. 2 shows the variation of the tensile modulus at different glass fiber loading. Tensile
modulus is increasing with increase in glass fiber loading in accordance with the results of other
researchers [8, 9, 10, 11, 12, 13]. The percentage increase in modulus is found to be 9.1 for glass
fiber loading up to 15wt%. From 15wt% to 20wt%, increase in modulus is 15% which is significant.
This is attributed to the higher modulus of glass fiber than the jute fiber and PP matrix. Normally, the
fibers in the composite restrain the deformation of the polymer matrix, reducing the tensile strain.
During tensile loading, partially separated micro spaces are created, which obstruct stress
propagation between the fibers and matrix. As the glass fiber loading increases, the degree of
obstruction increases, which consequently increases the stiffness. Range of the tensile modulus in the
current work is found to be 1482.52–1864.66 MPa.

200
3.2. Flexural properties
Flexural strength of jute fiber composites at different weight percentages of glass fiber
loading in the composite are shown in Fig. 3. It increased with fiber loading. This is in accordance
with the findings of other researchers [8, 9, 10, 11, 12, 13]. It is found that the flexural strength
increased by 20.82% up to a glass fiber loading of 20wt%. This is due to the fact that some of the
glass fibers are fractured, some are pulled out of matrix and some are still adhering to the matrix. The
glass fibers in the portions of the matrix are getting aligned in the direction perpendicular to the
application of the load. These observations justify the increase in load bearing capacity of the
material. The range of the flexural strength obtained is 38.8–46.88 MPa.
Variation in flexural modulus of jute and glass fiber hybrid composites at different glass fiber
loading is shown in Fig. 4. Flexural modulus is increasing almost linearly upto 15wt% of glass fiber
loading. Percentage increase is 13.32 (from 5wt% to 15wt%). Further loading of glass fiber is
increasing the modulus significantly. This increase is 26%. Investigations of several other
researchers have shown the same trend [8, 9, 10, 11, 12, 13]. Since glass fiber is a high modulus
material compared to jute fiber and matrix, higher fiber concentration demands higher stress for the
same deformation. The range of the flexural modulus obtained is 2132.64–2687.4 MPa
3.3. Impact properties
Variation of Izod impact strength with jute and glass fiber composites at different glass fiber
loadings are shown in Fig.5. Impact strength of the fiber reinforced composites depends on the
nature of the fiber, polymer and fiber–matrix interfacial bonding. It could be seen that the impact
strength is increasing with increase in percentage of glass fibers in the composite. For the synthetic
fiber addition to natural fiber reinforced composites, impact strength increase with glass fiber loading
[9, 11, 13]. There is increase in impact strength by 74.26% with increase in glass fiber loading up to
20%. Impact strength in fiber reinforced composites is caused by fiber fracture and fibers pull out.
More energy is required to fracture the composite than it is required for fiber pull out. Since the
failure of the specimen is mainly by fiber fracture and due to good interfacial adhesion between glass
fiber and the matrix, strength is increasing with increase in glass fiber content. The range of the
impact strength found in the current work is 4.43–7.72 KJ/m2
.
3.4. Hardness properties
In the hardness test, hardness was found to increase with increase in the quantity of glass
fiber content as observed from figure 6. For glass fiber addition to natural fiber reinforced
composites, the hardness increased with glass fiber loading [13].This is due to decrease in flexibility
and increase in stiffness of composites as glass fibers have these charecteristics. The range of the
hardness found in the current work is 72–79.
3.5. SEM morphology
SEM micrograph of the tensile fractured surface of 20:20wt%, jute: glass fiber composite is
shown in Fig.7. It shows that failure of the specimen is mainly by glass fibers fracture, pull out of
some of the same (indicated by dark holes), and jute fiber pull out. Higher tensile forces are required
to fracture glass fibers and pulling them out from the matrix. Moreover, the micrographs are
indicating brittle fracture of glass fibers. One must also note that, jute fibers are not fractured but
they are pulled out of the matrix. Also, interfacial adhesion between glass fibers and matrix is
superior when compared with that of jute and matrix. The combined effect of fracture of most of the
glass fibers, pulling out of matrix of some of them and pulling of jute fibers which are embedded in
the regions where, fractured and glass fibers in the matrix are predominant, call for higher
magnitudes of forces to fracture the hybrid composite.

201
SEM micrograph of cracked specimen subjected to flexural test having 20wt%:20wt%, jute:
glass fiber composite is shown in fig.8. It can be clearly seen from the micrograph that, some of the
jute fibers are within the matrix and some fibers are pulled out from the matrix. One must note that
glass fibers and jute fibers are randomly distributed in the matrix prior to the test. It is clear from the
micrograph that, both glass and jute fibers are getting axially oriented when the bending load is
applied. This calls for higher magnitude of forces. Glass fibers are either pulled out or fractured.
Further, the matrix having the fibers is getting dilated forming cleavages. Cleavages also offer
resistance to the axial orientation of fibers. Owing to these reasons, during flexural studies, the
composite material has shown increasing resistance to the prevailing loads with addition of glass
fibers.
SEM micrograph of specimen of 20wt:20wt%, jute: glass fiber composite fractured surface
subjected to impact load is shown in fig 9. It could be seen that the failure is due to predominantly
glass fibers brittle fracture and jute fiber dilation and pull out. As the percentage of glass fibers
increases in the matrix, the above said reasons confirm that higher impact energy is required to fail
the hybrid composite. Superior interfacial adhesion between glass fibers and matrix and
disorientation of jute fibers from their original orientation are some of the reasons for the hybrid
composite having higher impact strength.
Fig.1 Variation of Tensile strength with Glass fiber content
Fig. 2 Variation of Tensile modulus with Glass fiber content

202
Fig. 3 Variation of Flexural strength with Glass fiber content
Fig. 4 Variation of Flexural modulus with Glass fiber content
Fig. 5 Variation of Impact Strength with Glass content

203
Fig. 6 Variation of Hardness Value with Glass fiber content
Fig.7 SEM micrograph of fractured specimen of tensile test at 20wt:20wt% Jute: glass fiber

204
Fig.8 SEM micrograph of cracked specimen of flexural at 20wt:20wt% Jute: glass fiber
Fig.9 SEM micrograph of fractured specimen of Impact test at 20wt:20wt% Jute: glass fiber

205
4. CONCLUSION
The mechanical properties such as tensile, flexural, Impact and hardness of the jute and glass
fibers reinforced hybrid composites were studied by different weight ratios of jute and glass fibers.
Tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength and hardness
of the composite were found to be increasing with increase in glass fiber content and the values were
found to be the maximum at 20:20 percentage by weight of jute and glass. The overall increase in
strength of the hybrid composite considering tensile and flexural studies is 25.31%. Percentage
increase in impact strength is 63 which is very significant. Increase in hardness is 9.7%. These
increases in properties of the studied material could make this applicable in components of
automobiles like, dash boards, seat bases, frontal and rear bumpers, aircraft interior paneling and
furniture.
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