De Gruter V K Singh
description
Transcript of De Gruter V K Singh
DOI 10.1515/secm-2013-0318 Sci Eng Compos Mater 2014; aop
Vinay K. Singh *
Mechanical behavior of walnut ( Juglans L.) shell particles reinforced bio-composite Abstract: In the present work walnut particle reinforced
composite material was developed. Ten wt%, 15 wt%,
20 wt% and 25 wt% (weight percentage) of walnut parti-
cles were mixed with epoxy resin (CY-230). Scanning elec-
tron microscopy (SEM) shows that the walnut particles
were well dispersed in the epoxy resin matrix. Addition
of walnut particles increased the modulus of elasticity
of the bio composite. Addition of walnut particles in bio
composite decreased the ultimate strength both in com-
pression and tension. However, addition of walnut par-
ticles in bio composite increased the hardness. Flexural
modulus of elasticity also increased with increasing wal-
nut particles weight percentage, whereas flexural strength
and strain decreased with increased weight percentage of
walnut particles.
Keywords: composite material; environment; polymer;
walnut particles.
*Corresponding author: Vinay K. Singh, College of Technology,
G. B. Pant University of Agriculture and Technology, Pantnagar,
Uttarakhand-263145, India, e-mail: [email protected]
1 Introduction Composite is a material formed with two or more compo-
nents, combined as a macroscopic structural unit with
one component as a continuous matrix, and other as rein-
forcements with significantly different physical or chemi-
cal properties, which remain separate and distinct on a
macroscopic level within the finished structure. Normally,
the matrix is the material that holds the reinforcements
together and has lower strength than the reinforcements.
Most commercially produced composites use a polymer
matrix material called as resin solution [1] .
Composite resin technology has continuously evolved
since its introduction by Bowen [2] as a reinforced Bis-GMA
system. A major breakthrough in composite technology
was the development of photo-curable resins [3] . Con-
tinued development resulted in materials with reduced
particle size and increased filler loading that significantly
improved the universal applicability of light-cured com-
posite resins [4] .
As epoxy resins are a good solvent they are widely used
in industrial applications because of their high mechani-
cal and adhesion characteristics and chemical resistance
together with their curability in a wide range of tempera-
tures without the emission of any volatile byproducts.
The properties of epoxy-based organic/inorganic filled
composites can be finely tuned by an appropriate choice
of the structures of epoxy pre-polymer and hardener, type
and amount of inorganic filler. The composites have many
advantages over traditional silica powder or inorganic
mineral filled materials, including lower cost, lighter
weight, environmental friendliness and recyclability.
With growing environmental awareness, ecologi-
cal concerns and new legislation, bio particle reinforced
plastic composites have received increasing attention
during recent decades. Particleboards are of very recent
origin. The important aspect that has impacted favorably
on the development of these composite materials is the
possibility of incorporating waste agro-waste (agricul-
tural residues including stalks of most cereal crops, rice
husks, coconut fibers, bagasse, maize cobs, peanut shells,
and other wastes) product and recycled plastics with the
advantage of a positive eco-environmental impact. Due to
a worldwide shortage of trees and environmental aware-
ness, research on the development of composite prepa-
rations using various waste materials is being actively
pursued [5 – 7] . Based on a literature search [6, 8 – 10] ,
among the possible alternatives, the development of com-
posites using agricultural byproducts or agro-waste mate-
rials are currently the center of attention.
Particleboards are among the most popular materials
used in interior and exterior applications such as floor,
wall and ceiling panels, office dividers, bulletin boards,
cabinets, furniture, counter tops and desk tops [11] . The
production of particleboard can be related to the decided
economic advantage of low cost raw wood material,
inexpensive agents and simple processing. Therefore,
agro-waste instead of wood is widely used in the manu-
facturing of particleboard. Among the raw materials are
almond shell [12] , wheat straw [13] , bamboo [14] , cotton
seed hulls [15] , flax shiv [16] , rice straw-wood [17] , vine
prunings [18] , coir pith [19] and wood flour [20] . Polymers
such as urea-formaldehyde, phenol-formaldehyde, mela-
mine formaldehyde, polyethylene and polyvinylidene are
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2 V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite
commonly used as binders. Urea formaldehyde is the most
economic and useful adhesive among these binders.
The aim in the preset investigation with the objectives
was to develop a composite material containing different
percentages of walnut particle as the filler material and
investigate the mechanical behavior of different composites.
2 Materials and methods
2.1 Matrix material
2.1.1 Epoxy resin CY-230
Epoxy resin is widely used in industrial applications
because of its high strength and mechanical adhesiveness
characteristic. It is also a good solvent and has good chem-
ical resistance over a wide temperature range. Araldite
CY-230 purchased from M/s Petro Araldite Pvt. Limited
(Chennai, India) was used in the present investigation.
2.1.2 Hardener HY951
Hardener HY-951 purchased from M/s Petro Araldite Pvt.
Limited (Chennai, India) was used as the curing agent. In
the present investigation 8 wt% hardener HY-951 with epoxy
resin (CY-230) was used in all the material developed. The
weight percentage of hardener used in the present investi-
gation was as per recommendation of Singh and Gope [21] .
2.2 Reinforcing element
2.2.1 Walnut particles
The walnut particles are residues widely generated in
high proportions in the agro-industry by the grinding of
walnut shell. It is generally light to dark brown in color.
The walnut shells are underutilized, renewable agricul-
tural material. In the present study weight fraction (V f ) of
walnut particles varied from 10 – 25. Walnut particle pur-
chased from Allied Buss., Haldwani, India.
2.3 Optimization of weight percentage
2.3.1 Hardener (HY-951)
According to Misra and Singh [22] the per cent elongation,
yield strength and Young modulus reached the maximum
at 8 wt% of hardener (HY-951) when mixed with resin (CY-
230). Therefore in the present study 8 wt% of HY-951 has
been used.
2.3.2 Walnut particles
It was mixed with the resin up to the limits and the flow-
ability of the mixture was maintained for the purpose of
pouring the mixture into the vertical mould. No compres-
sion load was applied in this arrangement. The size of the
walnut particles was controlled by sieving with ASTM 40
and ASTM 80.
2.4 Method
Epoxy resin (CY-230), hardener (HY-951), and walnut par-
ticles with different weight percentages were used. Differ-
ent weight percentage (wt%) of walnut particles (15, 20,
25, 30 wt%) and epoxy resin were mixed by mechanical
stirring at 3000 rpm. Based on the curing curve [23] , the
solution obtained by mixing of walnut particles with resin
was kept in the furnace at a temperature of 90 ± 10 ° C for
2 h [21] . At intervals of 30 min the solution was taken out
of the electric furnace and remixed by a mechanical stirrer
at the same speed. After 2 h the whole solution was taken
out and allowed to cool to 45 ° C. When a temperature of
45 ° C was attained the hardener HY-951 (8 wt%) was mixed
immediately [21] . Due to the addition of hardener a highly
viscous solution was obtained which was remixed at high
speed by the mechanical stirrer. The viscous solution so
obtained was poured into different moulds for sample
preparation. Tensile, compression and bending tests were
conducted on a 100 kN servo hydraulic universal testing
machine (ADMET, USA) under displacement mode of
control of 1 mm/min. The results are presented and dis-
cussed in subsequent sections.
3 Results
3.1 Density
Density is one of the most important properties of the par-
ticle board material. The density of walnut particles rein-
forced composite for various weight percentages along
with density of epoxy resin are presented in Table 1 .
Table 1 reveals that increase in weight percentage of
reinforced particles, i.e., the walnut particles in the resin
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V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite 3
solution decreases the density. This decrease in density of
25 wt% is about 1% of 10 wt%. The decrease in density can
be related to the fact that the walnut particles are light but
occupy a substantial amount of space. Hence there is a
general decrease in the density of all the composite mate-
rials with regard to the epoxy resin.
3.2 Water absorption capacity
Water absorption capacity is another crucial factor to be
taken into account when considering the effect of water
on the composite material developed. The soaking period
is 24 h taken as constant for all combinations of material.
The effect is presented in Table 2 .
The effect of water absorption was important in case
the material that has been developed when used for appli-
cations comes in contact of water. The water absorption
capacity was found to be higher for 25 wt% of walnut par-
ticle reinforced composite as compared with lower weight
percentage of walnut particles. This substantial increase
with regard to the epoxy resin could be because the
walnut particles here have maximum capacity for water
absorption compared to the resin particles.
3.3 Scanning electron microscope (SEM)
The state of dispersion of particles into the resin matrix
plays a significant role with regard to the mechanical
properties of the composite. In the present investiga-
tion SEM was carried out on LEO435V6 instrument and
voltage was kept 20 kV for bio composite containing dif-
ferent weight percentage of walnut particles to evaluate
the particle size, particle matrix interface and dispersion
of walnut particles in the epoxy resin matrix.
Figure 1 (A) and 1(B) show the SEM micrographs of dif-
ferent bio composite material investigated in the present
work. In all cases, good dispersion of walnut particles in
the resin matrix has been observed. Figure 1(A) and 1(B)
show the SEM micrograph of composite containing 10
wt% and 25 wt% of walnut particles, respectively. It is
seen in the figures that walnut particles are well dispersed
in the epoxy resin matrix in a preferred orientation.
Hence, from the above micrographs it is can be con-
cluded that due to uniform dispersion of walnut particles
in epoxy resin, a remarkable effect on the mechanical
properties may be obtained.
3.4 Mechanical properties
3.4.1 Tensile stress-strain curve
The mechanical properties of the walnut particles filled
epoxy resin bio composite materials were determined
by a 100 kN ADMET Servo hydraulic Universal Testing
Machine at 1 mm/min strain rate under displacement
control mode. The tensile stress-strain curve for walnut
particles reinforced composite materials containing
Table 1 Density of walnut particle reinforced composite.
S. no.
Walnut particle (10 wt%)
(g/cm 3 )
Walnut particle (15 wt%)
(g/cm 3 )
Walnut particle (20 wt%)
(g/cm 3 )
Walnut particle (25 wt%)
(g/cm 3 )
Epoxy (g/cm 3 )
1 1.169 1.161 1.159 1.157 1.179
2 1.172 1.167 1.164 1.156 1.184
3 1.168 1.163 1.159 1.157 1.186
Mean 1.168 1.161 1.159 1.156 1.179
SD 0.0020 0.0031 0.0029 0.0006 0.0036
Table 2 Water absorption capacity.
S. no.
Walnut particle (10 wt%)
Walnut particle (15 wt%)
Walnut particle (20 wt%)
Walnut particle (25 wt%)
Epoxy resin
1 0.554% 0.573% 0.581% 0.613% 0.543%
2 0.557% 0.579% 0.583% 0.629% 0.549%
3 0.548% 0.569% 0.582% 0.619% 0.546%
Mean 0.553% 0.573% 0.582% 0.620% 0.546%
SD 0.000045 0.00005 0.00001 0.00008 0.00003
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4 V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite
10 wt%, 15 wt%, 20 wt% and 25 wt% of walnut particles
reinforced composite is shown in Figure 2 . All tests were
conducted as per ISO in 100 kN Servo hydraulic Univer-
sal Testing Machine. Brittle behavior can be seen in the
stress strain diagram due to addition of walnut parti-
cles in the epoxy resin matrix for all weight percentages
of walnut particles. However, it is seen that beyond 10
wt% of walnut particle the stress strain behavior does
not increase, therefore there is no improvement in load
bearing capacity.
3.4.2 Tensile properties
Tensile tests were carried out at strain rates of 1 mm/min.
The properties of the walnut particle of 10, 15, 20 and
25 wt% reinforced composite are presented in Table 3 .
The results of the ultimate tensile strength, percent-
age elongation in length and modulus of elasticity are
shown in the Table 3 for strain rate of 1 mm/min. Remark-
able differences can be seen on the ultimate tensile
strength of the bio composite material between 10 wt%
and over 10 wt% of walnut particles. It can be noticed that
for all specimens the ultimate tensile strength is highest
for the 10 wt% of walnut reinforced composite and is
163 MPa. Also, 10 wt% of walnut reinforced composite is
shown as maximum percentage elongation from amongst
the composite materials. It is seen that addition of walnut
particles significantly affects the ultimate strength and
180
160
140
120
100
Str
ess
(MP
a)
80
60
40
10 wt% walnut powder
15 wt% walnut powder
20 wt% walnut powder
25 wt% walnut powder20
00.00 0.01 0.02 0.03 0.04 0.05
Strain0.06 0.07 0.08 0.09
Figure 2 Stress-strain diagram under tension for different wt% of walnut particles.
A
B
Figure 1 (A) 10 wt% of walnut particles. (B) 25 wt% of walnut
particles.
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V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite 5
percentage elongation. The ultimate tensile strength and
the modulus of elasticity of 10 wt% of walnut board are
almost 1.37 and 1.45 times higher than 15 wt% walnut
board, 1.43 and 1.51 times higher than 20 wt% walnut
board and 1.57 and 1.52 times higher than 25 wt% walnut
board. It is true for all particulate composite material;
no material can be fabricated which has more ultimate
strength from matrix material if reinforced material is
mixed at macro level. These behaviors are also shown in
Figure 3 .
On the basis of results obtained the effect of weight
fraction (V f ) on modulus of elasticity and ultimate strength
are shown in Equations 1 and 2 with a correlation coeffi-
cient greater than 0.99.
3 2
f f
f
Modulus of elasticity (MPa) -0.69V 42.44V
-858.1V 7040.0
= ++
(1)
3 2
f f
f
Ultimate strength (MPa) -0.058V 3.42V
-66.43V 544
= ++
(2)
3.4.3 Compressive strength
The compressive strength properties of the walnut particle
filled epoxy resin composite materials were determined
by 100 kN ADMET Servo controlled Universal Testing
machine at 1 mm/min strain rate under displacement
control mode.
The results of the compressive test are shown in
Table 4 . All tests were conducted under displacement
control mode. Stress strain diagram obtained from com-
pressive test is shown in Figure 4 .
A remarkable difference can be noticed in the value of
the compressive strength with different weight percentage
Table 3 Tensile properties of the composite materials.
Property
Walnut particle (10 wt%)
Walnut particle (15 wt%)
Walnut particle (20 wt%)
Walnut particle (25 wt%)
Ultimate tensile strength (MPa) 163.00 119.00 114.00 104.00
% Elongation in length 8.49 7.29 6.93 6.85
Modulus of elasticity (MPa) 2013.00 1388.00 1333.00 1328.00
205 9.0
8.5
Ultimate strength, MPa
Ulti
mat
e st
reng
th, M
odul
us o
f ela
stic
ity
Modulus of elasticity/10 MPa
% Elongation
Elo
ngat
ion
(%)
8.0
7.5
7.0
6.5
190
175
160
145
115
130
10010 12 14 16 18
Walnut particles (wt%)20 22 24
Figure 3 Variation of ultimate tensile strength, modulus of elasticity and elogation for different weight percentage of walnut reinforced
composite.
Table 4 Compressive properties of the composite materials.
Property
Walnut particle (10 wt%)
Walnut particle (15 wt%)
Walnut particle (20 wt%)
Walnut particle (25 wt%)
UTS (MPa) 261.00 231.00 191.00 135.00
% Reduction in length 49.95 46.61 45.69 31.48
Modulus of elasticity (MPa) 1578.00 1668.00 2321.00 2391.00
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6 V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite
fUltimate strength (MPa)=-8.36V +350.8.
(4)
3.4.4 Hardness
As known, hardness implies a resistance to indentation,
permanent or plastic deformation of material. In a bio
composite material, filler weight fraction significantly
affects the hardness value of the hybrid composite mate-
rial. Hardness values measured on the Rockwell M-scale
showing the effect of weight percentage of walnut par-
ticles on the hardness values of hybrid composite are
presented in Table 5 . Variation of hardness with walnut
particles weight percentage is shown in Figure 6 .
It is found that hardness of neat epoxy resin (CY-230
+ 8 wt% of HY-951) is 56.4 MRH. The hardness of the fab-
ricated composite made of epoxy resin and 25 wt% is the
maximum and is 89.8 MRH. The hardness increases with
increase in walnut particles weight percentage. Figure 7
shows that with increasing of hardness, ultimate strength
in compression as well tension deceases and material
behaved in a brittle manner.
Table 5 Rockwell hardness values on M-scale for various filled
hybrid composites.
S. no
Walnut (10 wt%)
Walnut (15 wt%)
Walnut (20 wt%)
Walnut (25 wt%)
Resin
1 R-63 R-67 R-77 R-90 R-57
2 R-64 R-65 R-81 R-87 R-55
3 R-61 R-66 R-79 R-89 R-58
4 R-60 R-68 R-80 R-91 R-57
5 R-63 R-64 R-78 R-92 R-55
Mean R-62.2 R-66 R-79 R-89.8 R-56.4
SD 1.6431 1.5811 1.5811 1.9235 1.3416
050
55
60
65
70
Har
dnes
s (M
RH
)
75
80
90
85
5 10 15Walnut particles (wt%)
20 25
Figure 6 Hardness (MRH) for different weight percentage of walnut
reinforced composite.
300
250
200
Str
ess
(MP
a)
150
100
50
00 0.1 0.2 0.3
Strain
10 wt% of walnut particle15 wt% of walnut particle20 wt% of walnut particle25 wt% of walnut particle
0.4 0.5
Figure 4 Stress-strain diagram under compression for different
wt% of walnut particles.
310
280
250
220
190
160
13010 15 20
Walnut particles (wt%)25
30
35
40
50
45
Ultimate strength, MPa
% Reduction in length
Mod
ulus
of e
last
icity
, Ulti
mat
e st
reng
th
Modulus of elasticity/10 MPa
Red
uctio
n in
leng
th (
%)
Figure 5 Ultimate strength for different weight percentage of
walnut reinforced composite.
composition of walnut particle. It can be noticed that
addition of walnut particle improves the modulus of elas-
ticity of composite materials. It is found that ultimate com-
pressive strength of 10 wt% of walnut is about 261.0 MPa.
But increase in weight percentage of walnut particles, the
ultimate strength decreases considerably. Hence, taking
into consideration the requirement and the cost effective-
ness various composition of the reinforced material can be
taken. Variation in ultimate strength, percentage reduc-
tion in length and modulus of elasticity with respect to
different weight percentage walnut reinforced composite
are shown in Figure 5 .
On the basis of results obtained the effect of weight
fraction (V f ) on modulus of elasticity and ultimate strength
are shown in Equations 3 and 4 with a correlation coeffi-
cient >0.9.
fModulus of elasticity (MPa)=61.84V +907.3
(3)
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V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite 7
The present result shows that a linear relation between
hardness and ultimate strength in tension and compres-
sion exists. The following correlation between hardness
and ultimate strength has been developed (Equations 5
and 6) with a correlation coefficient >0.9, where H is hard-
ness in MRH scale.
Ultimate compressive strength (MPa) -4.280H 522.3= +
(5)
Ultimate tensile strength (MPa)=-1.648H 247.3.+
(6)
3.4.5 Flexural strength
The flexural strength of the walnut particle filled epoxy
resin composite materials were determined by 100 kN
ADMET make servo controlled universal testing machine
at 1 mm/min strain rate under displacement control mode
using three point bend test. The results are presented in
Table 6 .
As depicted by the test data, amongst the composite
materials developed the 25 wt%, walnut reinforced com-
posite shows the best results with regard to the flexural
modulus of elasticity (1560 MPa) and also it is better than
10 wt% walnut reinforced composites with regard to the
flexural modulus of elasticity. But flexural stress and flex-
ural strain was found to be higher for 10 wt% walnut filled
composites as compared with others investigated in this
report.
4 Conclusions Epoxy bio composites reinforced with walnut particles
were prepared. Such bio composites were experimentally
characterized by means of microscopy, tensile, compres-
sion, hardness and bending test. Remarkable changes
in the mechanical properties have been noticed due to
addition of walnut particles in bio composite. Addition
of walnut particles increased the hardness, which is very
important property for particles board with sustainable
tensile and compressive properties.
Acknowledgments: The author expresses his gratitude
and sincere thanks to Department of Science and Technol-
ogy, India, for providing finance to carry out this research
work smoothly.
Received December 16 , 2013 ; accepted January 2 , 2014
280
260
240
Ultimate strength (compression)
Ultimate strength (tension)
220
200
Ulti
mat
e st
reng
th (
MP
a)
180
160
140
120
10060.0 70.0 80.0
Hardness (MRH)90.0
Figure 7 Variation of ultimate strength with hardness (MRH).
Table 6 Flexural strength properties for resin and composites materials.
Properties
Walnut particle (10 wt%)
Walnut particle (15 wt%)
Walnut particle (20 wt%)
Walnut particle (25 wt%)
Flexural modulus (MPa) 1360.0 1450.0 1500.0 1560.0
Flexural stress (MPa) 769.0 614.0 603.0 439.0
Flexural strain 0.057 0.042 0.040 0.028
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8 V.K. Singh: Mechanical behavior of walnut shell particles reinforced bio-composite
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