A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
805–811
EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE
MECHANICAL PROPERTIES AND EROSIVE-WEAR BEHAVIOR
OF A WOOD-DUST-PARTICLE-REINFORCED PHENOL
FORMALDEHYDE COMPOSITE
VPLIVI DODATKA KOKOSOVIH VLAKEN
FENOL-FORMALDEHIDNEMU KOMPOZITU, OJA^ANEM Z
LESNIM PRAHOM, NA NJEGOVE MEHANSKE LASTNOSTI IN
EROZIJSKO OBRABO
Arul Sujin Jose1, Ayyanar Athijayamani2, Kalimuthu Ramanathan3,
Susaiyappan Sidhardhan4
1Lourdes Mount College of Engineering and Technology, Department of Mechanical Engineering, Kanyakumari, Tamilnadu, India
2Government College of Engineering, Department of Mechanical Engineering, Bodinayakkanur, Tamilnadu, India
3Alagappa Chettiar College of Engineering and Technology, Department of Mechanical Engineering, Karaikudi, Tamilnadu, India
4Government College of Engineering, Department of Civil Engineering, Tirunelveli, Tamilnadu, India
athimania@gmail.com
Prejem rokopisa – received: 2016-09-23; sprejem za objavo – accepted for publication: 2017-01-22
doi:10.17222/mit.2016.284
Several attempts were made to investigate the effects of various process parameters on the mechanical properties and wear
behavior of synthetic and natural cellulosic fibers and also particle-reinforced polymer composites. However, very few studies
were carried out on the effects of various process parameters on the mechanical and wear behavior of phenol formaldehyde (PF)
composites reinforced with natural cellulosic fibers and particles. Therefore, in the present study, an attempt was made to
observe the effects of various process parameters on the mechanical and wear behavior of wood-dust (WD) and coir-pith (CP)
particle-reinforced resole-type PF composites. First, the mechanical properties of a WD/PF composite were studied based on the
content of CP particles. Then, the erosive-wear behavior of the WD/PF composite was studied with respect to five different
parameters such particle content, erodent size, impact velocity, impingement angle, and standoff distance. The erosive
experiments were carried out for five different parameters based on the Taguchi experimental design (L27). The results show that
the mechanical properties of the WD/PF composite increase with an addition of CP particles. The increment in the composite
modulus was higher than that of the composite strength. The erosive test results indicate that the erosion-wear rate is affected by
the particle content, impingement angle, erodent size and impact velocity. Brittle-erosion behavior was identified on the surface
of the composite with a heavy erosive wear occurring at a 60° impingement angle.
Keywords: biowaste particles, phenol formaldehyde, composites, mechanical properties, erosive-wear resistance, Taguchi
method
Izvedenih je bilo `e kar nekaj poizkusov v zvezi z u~inki razli~nih procesnih parametrov na mehanske lastnosti in obrabo
polimernih kompozitov oja~anih s sinteti~nimi in naravnimi celuloznimi vlakni in/ali delci. Toda zelo malo raziskav je bilo
izvedenih glede vpliva razli~nih procesnih parametrov na mehanske lastnosti in obrabo fenolformaldehidnih (angl. PF)
kompozitov, oja~anih z naravnimi celuloznimi vlakni in delci. Tako je v pri~ujo~em delu predstavljen vpliv razli~nih procesnih
parametrov na mehanske lastnosti in obrabo PF kompozitov, ki so bili oja~ani z delci lesnega prahu (angl. WD) in delci kokosa
(angl. CP). Te vrste kompozitov se uporabljajo za izdelavo podplatov ~evljev. Najprej so bile dolo~ene mehanske lastnosti
WD/PF kompozitov glede na vsebnost CP delcev. Sledili so preizkusi in analize erozijske obrabe WD/PF kompozitov glede na
vsebnost (koli~ino) delcev v kompozitu, velikost, hitrost in razdaljo u~inkovanja erozijskega sredsta ter njegov vpadni kot.
Preizkusi so temeljili na analizi s Taguchijevo metodo (L27) s petimi razli~nimi parametri. Rezultati so pokazali, da se mehanske
lastnosti WD/PF kompozitov izbolj{ujejo z dodajanjem CP delcev. Povi{anje modula kompozitov je bilo ve~je od pove~anja
trdnosti kompozita. Erozijski testi ka`ejo, da je hitrost erozijske obrabe posledica vseh procesnih parametrov, to je: vsebnosti
delcev, udarnega kota, hitrosti in velikosti delcev izbranega erozijskega sredstva. Najve~ja obraba zaradi erozije je bila dose`ena
(ugotovljena) pri 60 stopinjskem vpadnem kotu abrazijskega sredstva z nastalimi po{kodbami krhkega zna~aja.
Klju~ne besede: delci bioodpadkov, fenolformaldehid, kompoziti, mehanske lastnosti, odpornost proti erozijski obrabi, Taguchi
metoda
1 INTRODUCTION
Recently, polymer composites reinforced with syn-
thetic materials have been replaced with polymer com-
posites reinforced with bio-based natural materials. The
bio-based natural materials have many advantages over
the synthetic materials like renewability, biodegrada-
bility, abundant availability, low costs, etc.1–3 In India,
particularly in the South Indian region, the biowaste
materials like wood dust, coir pith, groundnut shell,
coconut shell, cashew nut shell, etc. are abundantly
available because in that region, coconut, groundnut and
cashew nut are cultivated in large amounts. A number of
timber and oil mills are also available in the Southern
region of Tamilnadu, India. Therefore, bioparticles are
thrown away after producing useful materials and
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 805
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 67.017:620.1:620.163 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(5)805(2017)
dumped on the land of the village nearest to these in-
dustries.
Many studies have already reported on the properties
of different bio-based natural-fiber-reinforced polymer
composites in different conditions.3–7 But, only few
reports are available on the properties of polymer com-
posites filled with biowaste particles.8–11 In this investi-
gation, an attempt was made to study the mechanical and
wear behavior of PF composites reinforced with
biowaste particles (WD and CP). Mechanical properties
of wood-dust-particle-reinforced PF composites were
evaluated based on the content of coir pith. The erosive-
wear behavior of the composites was studied using five
different parameters such as particle content, erodent
size, impingement angle, impact velocity and standoff
distance. The erosive experiments were conducted as per
the Taguchi experimental design. The parameters used
for erosive-wear tests were also analyzed using an
analysis of variance with the wear rate.
2 MATERIALS AND METHODOLOGY
2.1 Materials
Wood-dust particles were collected from the Kumar
Timber and Sawmill, Karaikudi, Tamilnadu, India.
Coir-pith particles were collected from the Coir Industry,
Sozhavanthan, Tamilnadu, India. From the collected
wood-dust and CP particles, microparticles with the
average size of 800 microns were separated using a
sieving machine available in our composite laboratory.
The resole-type PF liquid resin was procured, together
with a cross-linking agent (divinylbenzene) and acidic
catalyst (hydrochloric acid), from POOJA Chemicals,
Madurai, Tamilnadu, India.
2.2 Preparation of the composites
A hardboard mold box with dimensions of 150 mm ×
150 mm × 3 mm was used to prepare the wood-dust and
coir-pith-particle composite plates using the hand lay-up
technique. Wood dust/coir pith/phenol formaldehyde
composites were fabricated at three different concentra-
tions of wood-dust and coir-pith particles, i.e., (20, 30 and
40) % mass fractions. The amount of WD particles was
maintained at a fixed level of 20 % mass fraction. Three
different amounts of CP particles (0–20 % mass frac-
tions) were hybridized with the constant amount of WD
particles, i.e., 20WD/0CP, 20WD/10CP, 20WD/20CP.
The weight percentage of WD and CP particles and
designation of the composites are given in Table 1. Prior
to the process, the particles were dried in sunlight for
12 h. The PF resin with the particles was mixed with a
mechanical stirrer at room temperature for 30 min. Then,
the cross-linking agent and acidic catalyst were also
mixed into the mixture of phenol formaldehyde/particles
and once again stirred with the mechanical stirrer for 15
min. After that, the mixture was poured into the mold
box and allowed to cure at room temperature for 48 h.
2.3 Testing composite specimens
Composite specimens were characterized using me-
chanical tests such as tensile, flexural and impact tests.
The tensile tests were conducted on an FIE universal
testing machine (UTE 40 HGFL) in accordance with
ASTM D638-10.12 The flexural tests were performed on
the same testing machine in accordance with ASTM
D790-10.13 The impact tests were carried out on an Izod
impact machine according to ISO 180.14 All the tests
were conducted at room temperature and atmospheric
pressure.
2.4 Taguchi experimental design
The erosive behavior of the WD/CP/PF composite
was studied based on the Taguchi method and analysis of
variance techniques. Experiments were performed as per
Taguchi experimental design (an orthogonal array)
because it is a systematic and efficient approach to get
the optimum range of process parameters with a good
performance. The number of experiments can be reduced
due to the constructed orthogonal array, which provides a
set of well-balanced experiments.15 The results obtained
with this experimental design are transformed into
signal-to-noise (S/N) ratios, which serve as objective
functions for the optimization of parameters and help
with the result analysis. There are three S/N ratios
available for the optimization of several static problems:
the smaller-the-better (used to minimize the response),
the nominal-the-better (used whenever an ideal quality is
equated with a particular nominal value.) and the larger-
the-better ratio (used to maximize the response). Among
these three characteristics, the minimum erosion rate
comes under the smaller-the-better characteristic, which
can be expressed as Equation (1):
S/N = –10 Log10 (1)
(the mean of the sum of squares of the measured data)
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
806 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Table 1: The weight percentage of WD and CP particles and designation of the composites
Total weight percentage
of particles in the
composites
Weight percentage of
resin
Weight percentage of
WD particles
Weight percentage of
CP particles
Designation of
composites
20 80 20 0 20WD/0CP
30 70 20 10 20WD/10CP
40 60 20 20 20WD/20CP
The five different process parameters at three levels
are used in this study to observe the erosive behavior of
the WD/CP/PF composite. Therefore, the actual number
of experiments, based on the traditional experimental
design, should be 243 (35). But, this number is reduced
to 27 experiments using the Taguchi technique. The pro-
cess parameters and their setting levels for the erosion
test of the WD/CP/PF composite are presented in Table
2. In these experiments, the following parameters are
fixed throughout the process: the type of erodent is
silica, the erodent feed rate is 10.0±1.0 g/min, the nozzle
length is 80 mm, and the nozzle diameter is 3 mm.
Table 2: The erosive process parameters with their designation and
setting levels
Process Parameters and their
designation Level I Level II Level III
Particle content: (A) wt% 20 30 40
Impact velocity: (B) m/sec 41 52 63
Impingement angle: (C) degree 30 60 90
Erodent size: (D) ìm 300 500 700
Stand-off distance: (E) mm 80 120 160
2.5 Erosion test
The erosive tests of the WD/CP/PF composite speci-
mens were conducted as shown in the schematic diagram
of the erosion process (Figure 1). The main components
of the erosion-test apparatus are the erodent feeder box,
erodent feeder nozzle, mixing chamber, nozzle of the
mixing chamber, air-flow vent, sample holder and ero-
dent collector. Dry silica sand with three different sizes
(300, 500 and 700) μm was used as the erodent in the
erosion tests. After the test, the composite samples were
taken from the apparatus and cleaned with acetone.
Then, the cleaned composite specimens were dried and
weighed using a precision digital balance at an accuracy
of ±0.1 mg. The composite samples were weighed before
and after the erosion tests and their difference is termed
as the weight loss. Then, the weight loss was recorded
and used for the erosion-rate calculation. Generally, the
erosion rate can be obtained as the ratio of the weight
loss of samples to the weight of the eroding particle. The
process was repeated until the steady-state erosion was
reached.
3 RESULTS AND DISCUSSION
3.1 Mechanical properties of the composites
Mechanical tests were carried out on the WD/CP/PF
composites and their results are presented in Figure 2a.
The neat-resin sample had a tensile strength of 29.8
MPa, tensile modulus of 1168.4 MPa, flexural strength
of 34.7 MPa, flexural modulus of 1257.4 MPa, and
impact strength of 1.24 KJ/m2. It can be seen that the
tensile strength and modulus of the PF composite in-
crease with an increase in the particle content. The
tensile strength of the 20WD/PF composite is almost the
same as that of the neat-resin sample. It shows that the
addition of WD particles enhances the strength of the PF
composite. The WD/PF composite without the addition
of CP particles has a tensile strength of 30.4 MPa and
this value increases to 41.7 MPa with the incorporation
of 10 % mass fraction of CP particles; after that, it de-
creases to 36.8 MPa with the addition of 20 % mass
fraction of CP particles. This may be due to a poor
interfacial bonding between the particles and the matrix,
i.e., a weak transfer of stress. Moreover, the stress con-
centration in the PF matrix may be created due to the
corner edges of the irregularly shaped WD and CP parti-
cles.
Due to the addition of 10 % mass fraction and 20 %
mass fraction of CP particles, the tensile strength of the
WD/PF composite increases by about 37.17 % and
21.1 %, respectively. Figure 2a also shows the tensile-
modulus values of the WD/CP/PF composites with res-
pect to the particle content. The composite also reached
the tensile-modulus value of the neat-resin sample with
the particle addition of 20 % mass fraction. The tensile-
modulus value of the WD/PF composite increased with
the further addition of CP particles. The maximum mo-
dulus value was observed at 40 % mass fraction of the
particles.
The results of the flexural tests of the WD/CP/PF
composites with respect to the particle content are given
in Figure 2b. It is interesting to note that the flexural
strength and modulus of the WD/PF composite increase
with the addition of CP particles. The flexural strength of
the WD/PF composite is slightly lower than the value of
the neat-resin sample. The maximum values of the flexu-
ral strength and modulus were identified at the 40 %
addition. The flexural strength of the WD/PF composite
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 807
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: Schematic diagram of the erosive process of the WD/CP/PF
composite
dumped on the land of the village nearest to these in-
dustries.
Many studies have already reported on the properties
of different bio-based natural-fiber-reinforced polymer
composites in different conditions.3–7 But, only few
reports are available on the properties of polymer com-
posites filled with biowaste particles.8–11 In this investi-
gation, an attempt was made to study the mechanical and
wear behavior of PF composites reinforced with
biowaste particles (WD and CP). Mechanical properties
of wood-dust-particle-reinforced PF composites were
evaluated based on the content of coir pith. The erosive-
wear behavior of the composites was studied using five
different parameters such as particle content, erodent
size, impingement angle, impact velocity and standoff
distance. The erosive experiments were conducted as per
the Taguchi experimental design. The parameters used
for erosive-wear tests were also analyzed using an
analysis of variance with the wear rate.
2 MATERIALS AND METHODOLOGY
2.1 Materials
Wood-dust particles were collected from the Kumar
Timber and Sawmill, Karaikudi, Tamilnadu, India.
Coir-pith particles were collected from the Coir Industry,
Sozhavanthan, Tamilnadu, India. From the collected
wood-dust and CP particles, microparticles with the
average size of 800 microns were separated using a
sieving machine available in our composite laboratory.
The resole-type PF liquid resin was procured, together
with a cross-linking agent (divinylbenzene) and acidic
catalyst (hydrochloric acid), from POOJA Chemicals,
Madurai, Tamilnadu, India.
2.2 Preparation of the composites
A hardboard mold box with dimensions of 150 mm ×
150 mm × 3 mm was used to prepare the wood-dust and
coir-pith-particle composite plates using the hand lay-up
technique. Wood dust/coir pith/phenol formaldehyde
composites were fabricated at three different concentra-
tions of wood-dust and coir-pith particles, i.e., (20, 30 and
40) % mass fractions. The amount of WD particles was
maintained at a fixed level of 20 % mass fraction. Three
different amounts of CP particles (0–20 % mass frac-
tions) were hybridized with the constant amount of WD
particles, i.e., 20WD/0CP, 20WD/10CP, 20WD/20CP.
The weight percentage of WD and CP particles and
designation of the composites are given in Table 1. Prior
to the process, the particles were dried in sunlight for
12 h. The PF resin with the particles was mixed with a
mechanical stirrer at room temperature for 30 min. Then,
the cross-linking agent and acidic catalyst were also
mixed into the mixture of phenol formaldehyde/particles
and once again stirred with the mechanical stirrer for 15
min. After that, the mixture was poured into the mold
box and allowed to cure at room temperature for 48 h.
2.3 Testing composite specimens
Composite specimens were characterized using me-
chanical tests such as tensile, flexural and impact tests.
The tensile tests were conducted on an FIE universal
testing machine (UTE 40 HGFL) in accordance with
ASTM D638-10.12 The flexural tests were performed on
the same testing machine in accordance with ASTM
D790-10.13 The impact tests were carried out on an Izod
impact machine according to ISO 180.14 All the tests
were conducted at room temperature and atmospheric
pressure.
2.4 Taguchi experimental design
The erosive behavior of the WD/CP/PF composite
was studied based on the Taguchi method and analysis of
variance techniques. Experiments were performed as per
Taguchi experimental design (an orthogonal array)
because it is a systematic and efficient approach to get
the optimum range of process parameters with a good
performance. The number of experiments can be reduced
due to the constructed orthogonal array, which provides a
set of well-balanced experiments.15 The results obtained
with this experimental design are transformed into
signal-to-noise (S/N) ratios, which serve as objective
functions for the optimization of parameters and help
with the result analysis. There are three S/N ratios
available for the optimization of several static problems:
the smaller-the-better (used to minimize the response),
the nominal-the-better (used whenever an ideal quality is
equated with a particular nominal value.) and the larger-
the-better ratio (used to maximize the response). Among
these three characteristics, the minimum erosion rate
comes under the smaller-the-better characteristic, which
can be expressed as Equation (1):
S/N = –10 Log10 (1)
(the mean of the sum of squares of the measured data)
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
806 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Table 1: The weight percentage of WD and CP particles and designation of the composites
Total weight percentage
of particles in the
composites
Weight percentage of
resin
Weight percentage of
WD particles
Weight percentage of
CP particles
Designation of
composites
20 80 20 0 20WD/0CP
30 70 20 10 20WD/10CP
40 60 20 20 20WD/20CP
The five different process parameters at three levels
are used in this study to observe the erosive behavior of
the WD/CP/PF composite. Therefore, the actual number
of experiments, based on the traditional experimental
design, should be 243 (35). But, this number is reduced
to 27 experiments using the Taguchi technique. The pro-
cess parameters and their setting levels for the erosion
test of the WD/CP/PF composite are presented in Table
2. In these experiments, the following parameters are
fixed throughout the process: the type of erodent is
silica, the erodent feed rate is 10.0±1.0 g/min, the nozzle
length is 80 mm, and the nozzle diameter is 3 mm.
Table 2: The erosive process parameters with their designation and
setting levels
Process Parameters and their
designation Level I Level II Level III
Particle content: (A) wt% 20 30 40
Impact velocity: (B) m/sec 41 52 63
Impingement angle: (C) degree 30 60 90
Erodent size: (D) ìm 300 500 700
Stand-off distance: (E) mm 80 120 160
2.5 Erosion test
The erosive tests of the WD/CP/PF composite speci-
mens were conducted as shown in the schematic diagram
of the erosion process (Figure 1). The main components
of the erosion-test apparatus are the erodent feeder box,
erodent feeder nozzle, mixing chamber, nozzle of the
mixing chamber, air-flow vent, sample holder and ero-
dent collector. Dry silica sand with three different sizes
(300, 500 and 700) μm was used as the erodent in the
erosion tests. After the test, the composite samples were
taken from the apparatus and cleaned with acetone.
Then, the cleaned composite specimens were dried and
weighed using a precision digital balance at an accuracy
of ±0.1 mg. The composite samples were weighed before
and after the erosion tests and their difference is termed
as the weight loss. Then, the weight loss was recorded
and used for the erosion-rate calculation. Generally, the
erosion rate can be obtained as the ratio of the weight
loss of samples to the weight of the eroding particle. The
process was repeated until the steady-state erosion was
reached.
3 RESULTS AND DISCUSSION
3.1 Mechanical properties of the composites
Mechanical tests were carried out on the WD/CP/PF
composites and their results are presented in Figure 2a.
The neat-resin sample had a tensile strength of 29.8
MPa, tensile modulus of 1168.4 MPa, flexural strength
of 34.7 MPa, flexural modulus of 1257.4 MPa, and
impact strength of 1.24 KJ/m2. It can be seen that the
tensile strength and modulus of the PF composite in-
crease with an increase in the particle content. The
tensile strength of the 20WD/PF composite is almost the
same as that of the neat-resin sample. It shows that the
addition of WD particles enhances the strength of the PF
composite. The WD/PF composite without the addition
of CP particles has a tensile strength of 30.4 MPa and
this value increases to 41.7 MPa with the incorporation
of 10 % mass fraction of CP particles; after that, it de-
creases to 36.8 MPa with the addition of 20 % mass
fraction of CP particles. This may be due to a poor
interfacial bonding between the particles and the matrix,
i.e., a weak transfer of stress. Moreover, the stress con-
centration in the PF matrix may be created due to the
corner edges of the irregularly shaped WD and CP parti-
cles.
Due to the addition of 10 % mass fraction and 20 %
mass fraction of CP particles, the tensile strength of the
WD/PF composite increases by about 37.17 % and
21.1 %, respectively. Figure 2a also shows the tensile-
modulus values of the WD/CP/PF composites with res-
pect to the particle content. The composite also reached
the tensile-modulus value of the neat-resin sample with
the particle addition of 20 % mass fraction. The tensile-
modulus value of the WD/PF composite increased with
the further addition of CP particles. The maximum mo-
dulus value was observed at 40 % mass fraction of the
particles.
The results of the flexural tests of the WD/CP/PF
composites with respect to the particle content are given
in Figure 2b. It is interesting to note that the flexural
strength and modulus of the WD/PF composite increase
with the addition of CP particles. The flexural strength of
the WD/PF composite is slightly lower than the value of
the neat-resin sample. The maximum values of the flexu-
ral strength and modulus were identified at the 40 %
addition. The flexural strength of the WD/PF composite
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 807
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: Schematic diagram of the erosive process of the WD/CP/PF
composite
was increased by about 68.99 % due to the incorporation
of 20 % mass fraction of CP particles.
The impact-strength values of the WD/CP/PF com-
posites after the impact tests are presented in Figure 2c.
It can be seen that the impact strength of the WD/PF
composite is slightly lower than the value of the neat-
resin sample. It is also shown that the impact strength of
the WD/PF composite increases with the addition of 10
% mass fraction of CP particles, but it decreases with the
incorporation of 20 % mass fraction of CP particles. This
may be due to a poor adhesion between the particles and
the matrix. It may also be due to the stress concentration
of the resin matrix. It is also observed that the incor-
poration of 10 % mass fraction and 20 % mass fraction
of CP particles shows 15.57 % and 8.19 % higher impact
values compared to the WD/PF composite.
3.2 Steady-state erosion: effects of the impingement
angle
Generally, the erosive-wear behavior of polymer
composite materials can be categorized as brittle and
ductile. A ductile erosive situation is created in thermo-
plastic polymer composites, whereas the a brittle erosive
situation may be created in thermosetting polymer
composites. For the steady-state-erosion analysis of the
WD/CP/PF composites, an erosion test was carried out
based on eight different impingement angles (20, 30, 40,
50, 60, 70, 80 and 90)°, keeping all the other process
parameters constant (the initial level values).
The effects of the impingement angles on the erosion
rate of the WD/CP/PF composites are presented in Fig-
ure 3. From this figure, it can be observed that the
erosion rate is high at the impingement angle of 60° for
all the composite specimens, irrespective of the particle
content. However, a more brittle erosive behavior was
identified for the 40 % mass-fraction (20WD/20CP)
composite specimen. However, in the 20 % and 30 %
mass-fraction composite specimens, a semi-brittle
erosive behavior was identified. This may be due to the
addition of WD and CP particles to the PF composites.
When the higher amounts of particles are added to the
polymer material, it behaves as a typical brittle material.
Therefore, the brittleness of the composites with 20 %
mass fraction and 30 % mass fraction of particles is
lower than the composite with 40 % mass fraction of
particles. Due to this, a semi-brittle erosive situation
exists during the erosive process. It is also clear from
Figure 3 that the erosion rate increased with the increase
in the particle content. This may be due to the increased
hardness of the PF composite material caused by the
addition of WD and CP particles.
3.3 Analysis of the erosion rate
The erosion rates for 27 combinations of the erosive
experiments conducted on the WD/CP/PF composites
are given in Table 3. The erosion analysis was made
with popular software, namely, MINITAB 17. From
Table 3, it can be concluded that the parameter combina-
tion of particle loading-A (level II = 30 % mass fraction),
impact velocity-B (level I = 41 m/s), impingement
angle-C (level I = 30°), erodent size-D (level II = 500
um) and standoff distance-E (160 mm) gives the mini-
mum erosion rate (189. 8 mg/kg). Moreover, another
parameter combination (experiment number 4) allows
the next level of the minimum erosion rate (194.1
mg/kg). The difference between these two erosion rates
is small, as seen from Table 3. Anyway, the first para-
meter combination mentioned above is recognized as the
better combination of parameters to obtain the minimum
erosion rate. The overall mean of the signal-to-noise
ratio for the erosion rate is found to be 49.75 dB.
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
808 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 3: Steady-state erosive behavior of WD/CP/PF composites for
eight different impingement angles
Figure 2: Variation of: a) tensile property, b) flexural property, and c)
impact strength based on the particle content
The effects of five erosive-process parameters on the
erosion rate are graphically presented in Figure 4a.
From this figure, it can be clearly concluded that para-
meter A (the particle content), parameter B (the impact
velocity) and parameter C (the impingement angle) are
the most significant parameters. Parameter E (the stan-
doff distance) shows a moderately significant influence,
while parameter D (the erodent size) has a relatively less
significant influence. Figure 4b shows the interaction
between the erosive parameters. From this figure, it is
observed that a moderate interaction exists between para-
meters A and B, and between A and C. The interaction
between parameters B and C is below the moderate level.
Figures 5a to 5c show 3D surface plots of the ero-
sion rate with significant process parameters. The
observation is similar to the one made of the interaction
plots of the erosion rate. From the erosion test analysis
of the WD/CP/PF composites, it can be concluded that
the erodent size is most insignificant for the erosion rate.
The standoff distance shows relatively less significance
when compared to the other three process parameters
(particle content, impact velocity and impingement
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 809
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 5: 3D surface plots of erosion rate vs process parameters:
a) A × B, b) A × C, and c) B × C
Figure 4: a) Effects of erosive-process parameters and b) effects of
interactions of erosive-process parameters on the erosion rate
Table 3: The erosion rates and their S/N ratio of WD/CP/PF compo-
sites for 27 combinations
Experi
ment
No.
A B C D E
Erosion
rate
mg/kg
S/N
ratio
dB
1 20 41 30 300 80 209.5 -46.42
2 20 41 60 500 120 273.8 -48.75
3 20 41 90 700 160 220.7 -46.87
4 20 52 30 500 120 194.1 -45.76
5 20 52 60 700 160 267.3 -48.54
6 20 52 90 300 80 246.2 -47.82
7 20 63 30 700 160 211.9 -46.52
8 20 63 60 300 80 301.3 -49.58
9 20 63 90 500 120 277.1 -48.85
10 30 41 30 500 160 189.8 -45.65
11 30 41 60 700 80 343.5 -50.72
12 30 41 90 300 120 312.7 -49.90
13 30 52 30 700 80 298.9 -49.51
14 30 52 60 300 120 367.2 -51.29
15 30 52 90 500 160 351.3 -50.91
16 30 63 30 300 120 300.8 -49.56
17 30 63 60 500 160 378.5 -51.56
18 30 63 90 700 80 361.9 -51.17
19 40 41 30 700 120 332.8 -50.44
20 40 41 60 300 160 387.5 -51.76
21 40 41 90 500 80 370.6 -51.37
22 40 52 30 300 160 359.1 -51.10
23 40 52 60 500 80 398.3 -52.00
24 40 52 90 700 120 381.7 -51.63
25 40 63 30 500 80 379.2 -51.58
26 40 63 60 700 120 427.6 -52.62
27 40 63 90 300 160 369.8 -51.36
was increased by about 68.99 % due to the incorporation
of 20 % mass fraction of CP particles.
The impact-strength values of the WD/CP/PF com-
posites after the impact tests are presented in Figure 2c.
It can be seen that the impact strength of the WD/PF
composite is slightly lower than the value of the neat-
resin sample. It is also shown that the impact strength of
the WD/PF composite increases with the addition of 10
% mass fraction of CP particles, but it decreases with the
incorporation of 20 % mass fraction of CP particles. This
may be due to a poor adhesion between the particles and
the matrix. It may also be due to the stress concentration
of the resin matrix. It is also observed that the incor-
poration of 10 % mass fraction and 20 % mass fraction
of CP particles shows 15.57 % and 8.19 % higher impact
values compared to the WD/PF composite.
3.2 Steady-state erosion: effects of the impingement
angle
Generally, the erosive-wear behavior of polymer
composite materials can be categorized as brittle and
ductile. A ductile erosive situation is created in thermo-
plastic polymer composites, whereas the a brittle erosive
situation may be created in thermosetting polymer
composites. For the steady-state-erosion analysis of the
WD/CP/PF composites, an erosion test was carried out
based on eight different impingement angles (20, 30, 40,
50, 60, 70, 80 and 90)°, keeping all the other process
parameters constant (the initial level values).
The effects of the impingement angles on the erosion
rate of the WD/CP/PF composites are presented in Fig-
ure 3. From this figure, it can be observed that the
erosion rate is high at the impingement angle of 60° for
all the composite specimens, irrespective of the particle
content. However, a more brittle erosive behavior was
identified for the 40 % mass-fraction (20WD/20CP)
composite specimen. However, in the 20 % and 30 %
mass-fraction composite specimens, a semi-brittle
erosive behavior was identified. This may be due to the
addition of WD and CP particles to the PF composites.
When the higher amounts of particles are added to the
polymer material, it behaves as a typical brittle material.
Therefore, the brittleness of the composites with 20 %
mass fraction and 30 % mass fraction of particles is
lower than the composite with 40 % mass fraction of
particles. Due to this, a semi-brittle erosive situation
exists during the erosive process. It is also clear from
Figure 3 that the erosion rate increased with the increase
in the particle content. This may be due to the increased
hardness of the PF composite material caused by the
addition of WD and CP particles.
3.3 Analysis of the erosion rate
The erosion rates for 27 combinations of the erosive
experiments conducted on the WD/CP/PF composites
are given in Table 3. The erosion analysis was made
with popular software, namely, MINITAB 17. From
Table 3, it can be concluded that the parameter combina-
tion of particle loading-A (level II = 30 % mass fraction),
impact velocity-B (level I = 41 m/s), impingement
angle-C (level I = 30°), erodent size-D (level II = 500
um) and standoff distance-E (160 mm) gives the mini-
mum erosion rate (189. 8 mg/kg). Moreover, another
parameter combination (experiment number 4) allows
the next level of the minimum erosion rate (194.1
mg/kg). The difference between these two erosion rates
is small, as seen from Table 3. Anyway, the first para-
meter combination mentioned above is recognized as the
better combination of parameters to obtain the minimum
erosion rate. The overall mean of the signal-to-noise
ratio for the erosion rate is found to be 49.75 dB.
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
808 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 3: Steady-state erosive behavior of WD/CP/PF composites for
eight different impingement angles
Figure 2: Variation of: a) tensile property, b) flexural property, and c)
impact strength based on the particle content
The effects of five erosive-process parameters on the
erosion rate are graphically presented in Figure 4a.
From this figure, it can be clearly concluded that para-
meter A (the particle content), parameter B (the impact
velocity) and parameter C (the impingement angle) are
the most significant parameters. Parameter E (the stan-
doff distance) shows a moderately significant influence,
while parameter D (the erodent size) has a relatively less
significant influence. Figure 4b shows the interaction
between the erosive parameters. From this figure, it is
observed that a moderate interaction exists between para-
meters A and B, and between A and C. The interaction
between parameters B and C is below the moderate level.
Figures 5a to 5c show 3D surface plots of the ero-
sion rate with significant process parameters. The
observation is similar to the one made of the interaction
plots of the erosion rate. From the erosion test analysis
of the WD/CP/PF composites, it can be concluded that
the erodent size is most insignificant for the erosion rate.
The standoff distance shows relatively less significance
when compared to the other three process parameters
(particle content, impact velocity and impingement
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 809
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 5: 3D surface plots of erosion rate vs process parameters:
a) A × B, b) A × C, and c) B × C
Figure 4: a) Effects of erosive-process parameters and b) effects of
interactions of erosive-process parameters on the erosion rate
Table 3: The erosion rates and their S/N ratio of WD/CP/PF compo-
sites for 27 combinations
Experi
ment
No.
A B C D E
Erosion
rate
mg/kg
S/N
ratio
dB
1 20 41 30 300 80 209.5 -46.42
2 20 41 60 500 120 273.8 -48.75
3 20 41 90 700 160 220.7 -46.87
4 20 52 30 500 120 194.1 -45.76
5 20 52 60 700 160 267.3 -48.54
6 20 52 90 300 80 246.2 -47.82
7 20 63 30 700 160 211.9 -46.52
8 20 63 60 300 80 301.3 -49.58
9 20 63 90 500 120 277.1 -48.85
10 30 41 30 500 160 189.8 -45.65
11 30 41 60 700 80 343.5 -50.72
12 30 41 90 300 120 312.7 -49.90
13 30 52 30 700 80 298.9 -49.51
14 30 52 60 300 120 367.2 -51.29
15 30 52 90 500 160 351.3 -50.91
16 30 63 30 300 120 300.8 -49.56
17 30 63 60 500 160 378.5 -51.56
18 30 63 90 700 80 361.9 -51.17
19 40 41 30 700 120 332.8 -50.44
20 40 41 60 300 160 387.5 -51.76
21 40 41 90 500 80 370.6 -51.37
22 40 52 30 300 160 359.1 -51.10
23 40 52 60 500 80 398.3 -52.00
24 40 52 90 700 120 381.7 -51.63
25 40 63 30 500 80 379.2 -51.58
26 40 63 60 700 120 427.6 -52.62
27 40 63 90 300 160 369.8 -51.36
angle). It can be concluded that the combination of the
parameters – the particle content at level II, the impact
velocity at level I and the impingement angle at level I –
gives the minimum erosion rate. Therefore, this com-
bination is recognized as the best combination of the
erosive-process parameters to get the minimum erosion
rate within the selected parameter range.
3.4 Analysis of the variance for the erosion rate
Taguchi’s analysis of variance can be used to find the
set of significant parameters as well as their interactions
in any system. In this study, ANOVA is used to under-
stand the contribution of the parameters to the erosion
rate and the effects of their interactions on the erosion
rate of the WD/CP/PF composite. The ANOVA results
for the erosion rate of the WD/CP/PF composite are
given in Table 4. The last column (p-value) in this table
indicates the highly significant parameters and their
main effects depend upon the value of p. The p values
for the particle content, impact velocity, impingement
angle and standoff distance are 0.000, 0.023, 0.003 and
0.186, indicating their great influence on the erosion rate
of the composite. The p values of the interactions of the
process parameters show a moderate significance and a
significance below the moderate level. Table 5 shows the
responses for the S/N ratio (the small-the-better charac-
teristic). The order of the erosive-process parameters
based on their contributions to obtain the minimum ero-
sion rate is the particle content, impingement angle,
impact velocity, standoff distance and erodent size.
Table 4: Analysis of variance for Means of erosion rate
Source DF Seq SS Adj SS Adj MS F P
A 2 81404 81403.9 40701.9 120.99 0.000
B 2 7520 7519.9 3759.9 11.18 0.023
C 2 25188 25188.1 12594.0 37.44 0.003
D 2 97 96.7 48.4 0.14 0.870
E 2 1778 1778.4 889.2 2.64 0.186
A*B 4 2698 2698.2 674.6 2.01 0.258
A*C 4 3305 3305.3 826.3 2.46 0.203
B*C 4 791 791.1 197.8 0.59 0.690
Residual
Error 4 1346 1345.6 336.4
Total 26 124127
Table 5: Response table for signal to noise ratios (smaller is better)
Level A B C D E
1 -47.68 -49.10 -48.51 -49.87 -50.02
2 -50.03 -49.84 -50.76 -49.61 -49.87
3 -51.54 -50.31 -49.99 -49.78 -49.37
Delta 3.86 1.21 2.25 0.26 0.65
Rank 1 3 2 5 4
3.5 Confirmation experiment
At the end of this study, we carried out a confirma-
tory experiment as the final test to validate the estimated
results obtained during the erosive analysis of the
WD/CP/PF composite. Therefore, the experimental
results were verified with the estimated results using the
confirmation test. This test was conducted to predict the
erosion rate caused by a new set of erosive-process-
parameter levels (A2B1C1E3). To predict the S/N ratio,
the following equation can be used:
S/Np = (A2-T) + (B1-T) + (C1-T) + (E3-T) + T (2)
where T is the overall experimental average of the S/N
ratio and S/Np is the value of the predicted S/N ratio.
The comparison results for the predicted and experimen-
tal S/N ratio of the optimum process parameters are
given in Table 6. The difference between the predicted
and experimental S/N ratio is 0.51, i.e., an error of
1.1 %. It proves that the model can predict the erosion
rate with a reasonable accuracy.
Table 6: Comparison results of predicted and experimental signal-
to-noise ratio of optimal process parameters
Optimal erosive process parameters
Predicted Experimental Difference
Parameter
level A2B1C1E3 A2B1C1E3
Predicted-
Experimental
Erosion rate
mg/kg 191.5 189.8 1.7
Signal-to-noise
ratio dB -46.17 -45.66
4 CONCLUSIONS
Mechanical properties of a WD/CP/PF composite
were analyzed based on the particle content. The results
show that the tensile strength of the WD/PF composite
increased with the addition of 10 % mass fraction of CP
particles, but decreased with the addition of 20 % mass
fraction of CP particles. The flexural properties of the
WD/PF composite increased with the increase in CP
particles. The impact strength of the WD/PF composite
also increased with the addition of 10 % mass fraction of
CP particles and decreased with further addition of CP
particles. The steady-state erosion analysis was carried
out for eight different impingement angles on the
WD/CP/PF composite. The composite with the lower
particle content shows a semi-brittle erosive behavior
with a higher erosion wear at the 60° impingement angle.
On the other hand, the composite with the higher particle
content showed a fully brittle nature of the erosive beha-
vior with a higher erosion wear at the 60° impingement
angle. From the erosive analysis of the WD/CP/PF com-
posite, the process parameters like the particle content,
impingement angle and impact velocity are found to be
the most significant parameters influencing the erosion
rate. The standoff distance shows a moderate influence
on the erosion rate, while the erodent size shows a less
significant influence on the erosion rate.
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
810 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
5 REFERENCES
1 G. K. Mani, J. B. B. Rayappan, D. K. Bisoyi, Synthesis and cha-
racterization of kapok fibers and its composites, J. of Appl. Sci., 12
(2012), 1661–1665, doi:10.3923/jas.2012.1661.1665
2 J. A. Khan, M. A. Khan, R. Islam, Mechanical, thermal and degra-
dation properties of jute fabric – reinforced polypropylene
composites: Effect of potassium permanganate as oxidizing agent,
Polym. Compos., 34 (2013), 671–680, doi:10.1002/pc.22470
3 S. Singh, D. Deepak, L. Aggarwal, V. K. Gupta, Tensile and flexural
behavior of hemp fiber reinforced virgin recycled HDPE matrix com-
posites, Procedia Mater. Sci., 6 (2014), 1696–1702, doi:10.1016/
j.mspro.2014.07.155
4 I. V. Surendra, K. V. Rao, K. V. P. P. Chandu, Fabrication and investi-
gation of mechanical properties of sisal, jute & okra natural fiber
reinforced hybrid polymer composites, Int. J. Eng. Trends Technol.,
19 (2015), 116–120, doi: 10.14445/22315381/IJETT-V19P220
5 D. Kurniawan, B. S. Kim, H. Y. Lee, J. Y. Lim, Effects of repetitive
processing, wood content, and coupling agent on the mechanical,
thermal, and water absorption properties of wood/polypropylene
green composites, J. Adhes. Sci. Technol., 27 (2013), 1301–1312,
doi:10.1080/01694243.2012.695948
6 E. Muñoz, J. A. García-Manrique, Water absorption behaviour and
its effect on the mechanical properties of flax fibre reinforced
bioepoxy composites, Int. J. Polym. Sci., (2015), 1–10, doi:10.1155/
2015/390275
7 M. G. A. Selvan, A. Athijayamani, Mechanical properties of fragrant
screwpine fiber reinforced unsaturated polyester composite: Effect of
fiber length, fiber treatment and water absorption, Fibers Polym., 17
(2016), 104–116, doi:10.1007/s12221-016-5593-x
8 S. I. Durowaye, G. I. Lawal, M. A. Akande, V. O. Durowaye, Me-
chanical properties of particulate coconut shell and palm fruit poly-
ester composites, Int. J. Mater. Eng., 4 (2014), 141–147,
doi:10.5923/j.ijme.20140404.04
9 L. Netra, S. Thomas, C. K. Das, R. Adhikari, Analysis of morpho-
logical and mechanical behaviours of bamboo flour reinforced
polypropylene composites, Nepal J. Sci. Technol., 13 (2012),
95–100, doi:10.3126/njst.v13i1.7447
10 M. A. M. M. Idrus, S. Hamdan, M. R. Rahman, M. S. Islam, Treated
tropical wood sawdust-polypropylene polymer composite: mecha-
nical and morphological study, J. Biomater. Nano-Biotechnol., 2
(2011), 435–444, doi:10.4236/jbnb.2011.24053
11 R. Panneerdhass, A. Gnanavelbabu, K. Rajkumar, Mechanical pro-
perties of luffa fiber and ground nut reinforced epoxy polymer hybrid
composites, Procedia Eng., 97 (2014), 2042–2051, doi:10.1016/
j.proeng.2014.12.447
12 ASTM D 638-10, Standard test method for tensile properties of
plastics, Annual Book of ASTM Standards, 08.01 (2010), 1–16,
ASTM International, West Conshohocken
13 ASTM D 790–10, Standard test methods for flexural properties of
un-reinforced and reinforced plastics and electrical insulating
materials, Annual Book of ASTM Standards, 08.01 (2010), 1–11,
ASTM International, West Conshohocken
14 ISO 180:2000, Plastics – determination of Izod impact strength, third
edition, ISO Central Secretariat, Switzerland, 2000
15 U. S. Rao, L. L. R. Rodrigues, Influence of machining parameters on
tool wear in drilling of GFRP composites –Taguchi analysis and
ANOVA methodology, Proc. of the Inter. Conf. on Advances in
Mechanical and Robotics Engineering – MRE 2014, 25–29,
doi:10.15224/978-1-63248-002-6-84
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811 811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
angle). It can be concluded that the combination of the
parameters – the particle content at level II, the impact
velocity at level I and the impingement angle at level I –
gives the minimum erosion rate. Therefore, this com-
bination is recognized as the best combination of the
erosive-process parameters to get the minimum erosion
rate within the selected parameter range.
3.4 Analysis of the variance for the erosion rate
Taguchi’s analysis of variance can be used to find the
set of significant parameters as well as their interactions
in any system. In this study, ANOVA is used to under-
stand the contribution of the parameters to the erosion
rate and the effects of their interactions on the erosion
rate of the WD/CP/PF composite. The ANOVA results
for the erosion rate of the WD/CP/PF composite are
given in Table 4. The last column (p-value) in this table
indicates the highly significant parameters and their
main effects depend upon the value of p. The p values
for the particle content, impact velocity, impingement
angle and standoff distance are 0.000, 0.023, 0.003 and
0.186, indicating their great influence on the erosion rate
of the composite. The p values of the interactions of the
process parameters show a moderate significance and a
significance below the moderate level. Table 5 shows the
responses for the S/N ratio (the small-the-better charac-
teristic). The order of the erosive-process parameters
based on their contributions to obtain the minimum ero-
sion rate is the particle content, impingement angle,
impact velocity, standoff distance and erodent size.
Table 4: Analysis of variance for Means of erosion rate
Source DF Seq SS Adj SS Adj MS F P
A 2 81404 81403.9 40701.9 120.99 0.000
B 2 7520 7519.9 3759.9 11.18 0.023
C 2 25188 25188.1 12594.0 37.44 0.003
D 2 97 96.7 48.4 0.14 0.870
E 2 1778 1778.4 889.2 2.64 0.186
A*B 4 2698 2698.2 674.6 2.01 0.258
A*C 4 3305 3305.3 826.3 2.46 0.203
B*C 4 791 791.1 197.8 0.59 0.690
Residual
Error 4 1346 1345.6 336.4
Total 26 124127
Table 5: Response table for signal to noise ratios (smaller is better)
Level A B C D E
1 -47.68 -49.10 -48.51 -49.87 -50.02
2 -50.03 -49.84 -50.76 -49.61 -49.87
3 -51.54 -50.31 -49.99 -49.78 -49.37
Delta 3.86 1.21 2.25 0.26 0.65
Rank 1 3 2 5 4
3.5 Confirmation experiment
At the end of this study, we carried out a confirma-
tory experiment as the final test to validate the estimated
results obtained during the erosive analysis of the
WD/CP/PF composite. Therefore, the experimental
results were verified with the estimated results using the
confirmation test. This test was conducted to predict the
erosion rate caused by a new set of erosive-process-
parameter levels (A2B1C1E3). To predict the S/N ratio,
the following equation can be used:
S/Np = (A2-T) + (B1-T) + (C1-T) + (E3-T) + T (2)
where T is the overall experimental average of the S/N
ratio and S/Np is the value of the predicted S/N ratio.
The comparison results for the predicted and experimen-
tal S/N ratio of the optimum process parameters are
given in Table 6. The difference between the predicted
and experimental S/N ratio is 0.51, i.e., an error of
1.1 %. It proves that the model can predict the erosion
rate with a reasonable accuracy.
Table 6: Comparison results of predicted and experimental signal-
to-noise ratio of optimal process parameters
Optimal erosive process parameters
Predicted Experimental Difference
Parameter
level A2B1C1E3 A2B1C1E3
Predicted-
Experimental
Erosion rate
mg/kg 191.5 189.8 1.7
Signal-to-noise
ratio dB -46.17 -45.66
4 CONCLUSIONS
Mechanical properties of a WD/CP/PF composite
were analyzed based on the particle content. The results
show that the tensile strength of the WD/PF composite
increased with the addition of 10 % mass fraction of CP
particles, but decreased with the addition of 20 % mass
fraction of CP particles. The flexural properties of the
WD/PF composite increased with the increase in CP
particles. The impact strength of the WD/PF composite
also increased with the addition of 10 % mass fraction of
CP particles and decreased with further addition of CP
particles. The steady-state erosion analysis was carried
out for eight different impingement angles on the
WD/CP/PF composite. The composite with the lower
particle content shows a semi-brittle erosive behavior
with a higher erosion wear at the 60° impingement angle.
On the other hand, the composite with the higher particle
content showed a fully brittle nature of the erosive beha-
vior with a higher erosion wear at the 60° impingement
angle. From the erosive analysis of the WD/CP/PF com-
posite, the process parameters like the particle content,
impingement angle and impact velocity are found to be
the most significant parameters influencing the erosion
rate. The standoff distance shows a moderate influence
on the erosion rate, while the erodent size shows a less
significant influence on the erosion rate.
A. SUJIN JOSE: EFFECTS OF AN ADDITION OF COIR-PITH PARTICLES ON THE MECHANICAL AND ...
810 Materiali in tehnologije / Materials and technology 51 (2017) 5, 805–811
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
5 REFERENCES
1 G. K. Mani, J. B. B. Rayappan, D. K. Bisoyi, Synthesis and cha-
racterization of kapok fibers and its composites, J. of Appl. Sci., 12
(2012), 1661–1665, doi:10.3923/jas.2012.1661.1665
2 J. A. Khan, M. A. Khan, R. Islam, Mechanical, thermal and degra-
dation properties of jute fabric – reinforced polypropylene
composites: Effect of potassium permanganate as oxidizing agent,
Polym. Compos., 34 (2013), 671–680, doi:10.1002/pc.22470
3 S. Singh, D. Deepak, L. Aggarwal, V. K. Gupta, Tensile and flexural
behavior of hemp fiber reinforced virgin recycled HDPE matrix com-
posites, Procedia Mater. Sci., 6 (2014), 1696–1702, doi:10.1016/
j.mspro.2014.07.155
4 I. V. Surendra, K. V. Rao, K. V. P. P. Chandu, Fabrication and investi-
gation of mechanical properties of sisal, jute & okra natural fiber
reinforced hybrid polymer composites, Int. J. Eng. Trends Technol.,
19 (2015), 116–120, doi: 10.14445/22315381/IJETT-V19P220
5 D. Kurniawan, B. S. Kim, H. Y. Lee, J. Y. Lim, Effects of repetitive
processing, wood content, and coupling agent on the mechanical,
thermal, and water absorption properties of wood/polypropylene
green composites, J. Adhes. Sci. Technol., 27 (2013), 1301–1312,
doi:10.1080/01694243.2012.695948
6 E. Muñoz, J. A. García-Manrique, Water absorption behaviour and
its effect on the mechanical properties of flax fibre reinforced
bioepoxy composites, Int. J. Polym. Sci., (2015), 1–10, doi:10.1155/
2015/390275
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