Mechanical and Tribological Behaviour of
Applied Mechanics and Materials Vols. 592-594 (2014) pp 1320-1324
Online available since 2014/Jul/15 at www.scientific.net
© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.592-594.1320
Mechanical and Tribological Behaviour of Epoxy Reinforced with
Nano-Al2O3 particles
R.V. Kurahattia*, A. O. Surendranathanb, A.V. Ramesh Kumarc, V. Auradid,
C. S. Wadagerie and S. A. Koria
a
R & D Centre, Dept. of Mech. Engg., BEC, Bagalkot - 587102, Karnataka, India
b
Dept. of Meta and Mater Engg, NITK, Surathkal, Karnataka, India
c
Naval Physical and Oceanographic Laboratory, Kochi - 682021, Kerala, India
d
R & D Centre, Dept. of Mech. Engg., SIT, Tumkur-572103, Karnataka, India
e
Dept. of Mech. Engg., MMEC, Belgaum-591113, Karnataka, India
*
[email protected], [email protected], [email protected],
[email protected], [email protected], [email protected]
Keywords: Epoxy, Nano-alumina, Mechanical properties, Friction and wear, SEM
Abstract: In the present work systematic study has been conducted to investigate the matrix
properties by introducing nanosize Al2O3 (particle size 100 nm, 0.5–10 wt %) fillers into an epoxy
resin. High shear mixing process was employed to disperse the particles into the resin. The
experimental results indicated that frictional coefficient and wear rate of epoxy can be reduced at
rather low concentration of nano-Al2O3. The lowest specific wear rate 0.7 x 10-4 mm3/Nm is
observed for the composites with 1 wt.% which is decreased by 65% as compared to unfilled epoxy.
The reinforcement of Al2O3 particles leads to improved mechanical properties of the epoxy
composites. The results have been supplemented with scanning electron micrographs to help
understand the possible wear mechanisms.
Introduction
Polymer composites are widely used as structural materials in aerospace, automotive and
chemical industries, as they provide lower weight alternatives to metallic materials. Gears, cams,
bearings and seals are tribological components, where the self-lubrication properties of polymers
and polymer composites are of special advantage. The incorporation of well-dispersed nano- or
micro-sized inorganic particles into a polymer matrix has been demonstrated to be quite effective to
improve the tribological properties of the polymer composites [1-8]. It was verified experimentally
by numerous researchers that nanoparticles of metallic or inorganic type, prove the ability to
reinforce effectively thermoplastic and also thermosetting polymer matrices [10]. Specifically, the
reinforcement covers improvements of the flexural modulus without loosing flexural strength. This
effect is at the same time accompanied by improvements in fracture toughness and impact energy
which, however, depend strongly on the filler volume content [11]. However, the unique nanocomposite effects can only be effective, if the nanoparticles are well dispersed in the surrounding
polymer matrix. It has been shown that, a considerable improvement of the mechanical and
tribological properties can already be achieved at very low filler volume content, somewhere in the
range of 1–5 vol% [12–14].
Epoxies exhibit superior qualities such as high glass transition temperature (Tg), high modulus,
high creep resistance, low shrinkage at elevated temperature and good resistance to chemicals due
to their densely cross-linked structure. Having ability to adhere to a variety of fillers, they are used
for high-performance coatings for tanks and structures. There are special grades of epoxy for
elevated-temperature service to about 176◦C. In the present work, nano-Al2O3 filled epoxy
composites have been prepared by using high shear mixing process for particle dispersion. The
filler content was varied in the range 0.5-10 wt%. The effect of filler content on mechanical and
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
www.ttp.net. (ID: 27.251.8.22-15/07/14,11:59:19)
Applied Mechanics and Materials Vols. 592-594
1321
tribological properties of the nanocomposites has been studied. Epoxy nanocomposites containing
100 nm alumina particles have not been studied. Hence the present work is taken up.
Experimental Details:
Epoxy resin LY 556 (diglycidayl ether of bisphenol A) and hardener HY951 (triethylene
tetramine) were supplied by Huntsman Advanced Materials Pvt. Ltd (Mumbai, India). Al2O3
nanoparticles were purchased from Sigma Aldrich (Bangalore, India). Al2O3 represents the ceramic
nanocrystalline phase and consists of primary particles in the size of 100 nm. They have a specific
surface area of 100m2/g. The epoxy resin of known weight (g) was taken in a beaker. Al2O3
nanoparticles were added into the resin. The mixture was stirred using a homogenizer (Miccra D-9,
speed range of 11 000–39 000 rpm) for 2 h. The high shear mixing results in the separation of
particle agglomerates. The hardener (10 wt% of resin) was then added into the mixture and stirred
for 15 min. The mixture was then poured into the mould. Curing of the composite at 25°C for 24 h
and post-curing at 70°C for 1 h were carried out. Composites with filler contents of 0.5, 1, 5 and 10
wt.% were prepared. Flexural tests of pure epoxy resin and the composites were carried out in a
UNITEK 9450 PC universal testing machine in accordance with the ASTM D790 standard at a
deformation rate of 1 mm/min, while un-notched impact tests were conducted in a FIE IT-30 tester.
The hardness of the materials was measured using an FIE RASNB Rockwell hardness tester with
‘F’ scale (1/16” diameter ball indenter and 60 kg load). A loading time of 30 s was used.
Unlubricated pin-on-disc sliding wear tests were carried out in order to determine the
tribological properties of the nanocomposites. Sliding was performed in air with the ambient
temperature of around 25°C over a period of 60 min. at a sliding velocity of 0.84 m/s and a normal
pressure of 0.8 MPa. The test samples were accurately weighed before and after the wear run using
electronic balance (0.1 mg accuracy) to determine the wear loss. The friction coefficient was
calculated by taking into account the normal load and the friction force. The wear performance is
described by specific wear rate (Ks):
where ∆ m is the mass loss in grams (g), ρ is the measured density of the sample in (g /mm3), FN is
the normal load in (N) and L is the sliding distance in meters (m). The average of the three readings
was adapted in our results. Scanning electron microscopy examinations on a Jeol-5400 was used to
study the morphology of fracture surfaces from flexural testing and the morphology of worn
surfaces.
Results and Discussions
Mechanical Properties: Table 1 shows the mechanical properties of the composites containing
different concentrations of Al2O3. It is seen that the flexural and impact strengths of the composites
are increased by the addition of nano-Al2O3, with the highest values being obtained at composites
containing 0.5 wt% nano-Al2O3. Nanocomposites impart a high portion of interface. The increase in
flexural strength and modulus suggests that stresses are efficiently transferred via the interface.
However, the flexural and impact strengths of the composites are decreased with increasing nanoAl2O3 content above 0.5 wt.%. Thus, it can be inferred that a higher content of Al2O3 is unfavorable
for increasing the mechanical properties of the composites. On the other hand, it can also be see that
the hardness of the composite is almost unchanged with increasing Al2O3 content. This implies that
nano-Al2O3 may be ineffective for increasing the load carrying capacity of the composites
containing nano-Al2O3. The hardness of the composites is not only one factor to determine the
tribological behaviour of materials. The interfacial interaction between the epoxy matrix and the
nano-Al2O3 may be also an important factor.
1322
Dynamics of Machines and Mechanisms, Industrial Research
Tribological behaviour: In general, the friction and wear properties do always describe the whole
tribological system rather than a material property alone. Fig. 1a shows the specific wear rate (Ks)
of the nanocomposites as a function of content of Al2O3 nanoparticles. It was found that the nanoAl2O3/epoxy composites exhibited decreased Ks in comparison to the neat epoxy. The Ks sharply
decreased when nano particle content was below 1 wt%. 1 wt% nano-Al2O3/epoxy exhibited the
lowest Ks. Although, the Ks increased with increasing Al2O3 content above 1 wt. %, it was still
Table1. Shows mechanical properties of epoxy composites containing different concentrations of
nano-Al2O3
Flexural strength
Impact strength
Hardness
Nano-Al2O3
2
MPa
kJ/m
content wt.%
Kg/mm2
0
36.9
18.68
83
0.5
94.7
31.87
83.5
1
56.6
16.85
82.8
5
34.7
16.36
80.34
10
41.4
18.19
81.8
lower compared to the neat epoxy. 1 wt.% nano-Al2O3/epoxy composite showed the Ks value of
0.7x10-4 mm3/Nm (- 65%) compared to the neat resin’s value of 2.0 x 10-4 mm3/Nm. Rong et al. [9]
examined the influence of microstructure on the tribological performance of nanocomposites by
different compounding methods. They confirmed that the dispersion state of the nanoparticles and
micro-structural homogeneity of the fillers improve the wear resistance significantly. The
phenomenon reported in the present work is similar to the one reported by Rong et al [9]. Besides
improving the wear resistance, the nanoparticles also reduce the coefficient of friction as shown in
Fig. 1b. Evidently, the nano-composite with 1 wt% Al2O3 has the lowest friction coefficient. The
coefficient of friction decreases from 0.57 for unfilled epoxy to 0.44 at 1 wt%. The detached
nanoparticles might also act as solid lubricant. These account for the lower specific wear rates and
friction coefficients of the nanocomposites.
(a)
(b)
Fig. 1. (a) Specific wear rate of unfilled epoxy and nano-Al2O3/epoxy composites (Normal pressure,
0.8MPa; Sliding velocity, 0.84m/s; sliding distance, 3014m) (b) Friction coefficient of
unfilled epoxy and nano-Al2O3/epoxy composites.
Worn surface studies: The morphologies of the worn pins’ surfaces were examined by SEM at an
identical magnification of 500 X (Figs. 2a-c). The main features on the worn surface of the neat
epoxy are severe damage characterized by the disintegration of the top surface, wear debris and
Applied Mechanics and Materials Vols. 592-594
1323
deep grooves in the sliding direction (Fig. 2a). In the case of filled nanocomposites, the appearances
are completely different and become rather smooth. Although the ploughing grooves are still visible
on the sample surface, the groove depths are shallow on 1 wt% filled epoxy (Fig. 2b) and at some
region, the grooves are simply invisible. It seems the low filler loading is sufficient and can bring
about significant improvement in wear resistance. During sliding, a rolling effect of nanoparticles
could reduce the shear stress, the friction coefficient and the contact temperature. The matrix
damages in the interfacial region were reduced by this rolling effect. However, the wear resistance
suffers if the filler loading exceeds 1 wt% and the large amount of nanoparticles cannot provide any
wear reducing effect. Abrasive wear is accompanied by delamination and fatigue cracking of the
matrix (Fig. 2c).
(a)
(b)
(c)
Fig. 2. Micro-photographs showing worn surface features of (a) unfilled epoxy, (b) 1wt% Al2O3
/epoxy and (c) 5 wt% Al2O3/epoxy nanocomposites.
Conclusions
This study focused on the development of nanocomposites with properties superior to the neat
matrix. The following conclusions can be drawn:
1. The reinforcement of Al2O3 leads to improved mechanical properties. Mechanical properties
do not exert remarkable influence on the wear behaviour of the materials.
2. The optimum wear resistant composition was found to be 1 wt% Al2O3 which exhibited the
decrement in sp. wear rate of -65% (0.7x10-4 mm3/Nm) compared to the neat resin’s value
of 2.0 x 10-4 mm3/Nm. Microscopic observation of the worn surfaces indicate a positive
rolling effect of the debris between the sample and the counterface.
1324
Dynamics of Machines and Mechanisms, Industrial Research
3. Nano-Al2O3 filled epoxy composites show signs of mild abrasive wear due to the hard
ceramic particles. The main wear mechanism of the composite changed from the severe
abrasive wear (for neat epoxy matrix) to mild abrasive wear.
Acknowledgements
The authors thank Director Dr K.U. Bhaskar Rao, DMSRDE Kanpur for permitting to conduct the
present research work.
References
[1]Q. Wang, Q. Xue, W. Liu and W. Shen, Tribological properties of micron silicon carbide filled
poly (ether ether ketone), J. Appl. Polym. Sci., Vol. 74 (1999), p. 2611–2615.
[2]J.M. Durand, M.Vardavoulias and M. Jeandin, Role of reinforcing ceramic particles in the wear
behavior of polymer-based model composites, Wear, Vol. 181–183 (1995), p. 833–839.
[3]M.Q. Zhang, M.Z. Rong, S.L. Yu, B. Wetzel and K. Friedrich, Effect of particle surface
treatment on the tribological performance of epoxy based nanocomposites, Wear, Vol. 253
(2002), p. 1086–1093.
[4]J.-C. Lin, Compression and wear behavior of composites filled with various nanoparticles,
Compos. Part B – Eng., Vol. 38 (2007), p. 79–85.
[5]S. Bahadur and D. Gong, The role of copper compounds as fillers in the transfer and wear
behavior of polyetheretherketone, Wear, Vol. 154 (1992), p. 151–165.
[6]S. Bahadur and D. Gong, The investigation of the action of fillers by XPS studies of the transfer
films of PEEK and its composites containing CuS and CuF2, Wear, Vol. 160 (1993), p. 131–138.
[7]B.J. Briscoe, A.K. Pogosian and D. Tabor, The friction and wear of high density polythene: The
action of lead oxide and copper oxide fillers, Wear, Vol. 27 (1974), p. 19–34.
[8]N.V. Klaas, K. Marcus and C. Kellock, The tribological behaviour of glass filled
polytetrafluoroethylene, Tribol. Int. Vol. 38 (2005), p. 824–833.
[9] M.Z. Rong, M.Q. Zhang, H. Liu, H.M. Zeng, B. Wetzel and K. Friedrich, Microstructure and tribological
behavior of polymeric nanocomposites, Ind. Lubr. Tribol., Vol. 53 (2001), p. 72–77.
[10] R.P. Singh, M. Zhang and D. Chan, Toughening of a brittle thermosetting polymer: effects
of reinforcement particle size and volume fraction, J Mater Sci., Vol. 37 (2002), p. 781–788.
[11] B. Wetzel, F. Haupert, K. Friedrich, M.Q. Zhang and M.Z. Rong, Mechanical and
tribological properties of particulate and nanoparticulate reinforced polymer composites, in:
Proceedings of the 13th ECCM Brugge, Belgium (2001).
[12] C.B. Ng, L.S. Schadler and R.W. Siegel, Synthesis and mechanical properties of TiO2-epoxy
nanocomposite, Nanostructured Materials, Vol. 12 (1999), p. 507–510.
[13] Q. Wang, W. Shen and Q. Xue Q, The friction and wear properties of nanometer SiO2 filled
polyetheretherketone, Tribo Int. Vol. 30 (3), (1997), p. 193–197.
[14] Q. Wang, W. Shen, Q. Xue and J. Zhang, The friction and wear properties of nanometer
ZrO2-filled poly-etheretherketone, J Appl Polym Sci, Vol. 69 (1998), p. 135–141.
Dynamics of Machines and Mechanisms, Industrial Research
10.4028/www.scientific.net/AMM.592-594
Mechanical and Tribological Behaviour of Epoxy Reinforced with Nano Al2O3 Particles
10.4028/www.scientific.net/AMM.592-594.1320
Online available since 2014/Jul/15 at www.scientific.net
© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.592-594.1320
Mechanical and Tribological Behaviour of Epoxy Reinforced with
Nano-Al2O3 particles
R.V. Kurahattia*, A. O. Surendranathanb, A.V. Ramesh Kumarc, V. Auradid,
C. S. Wadagerie and S. A. Koria
a
R & D Centre, Dept. of Mech. Engg., BEC, Bagalkot - 587102, Karnataka, India
b
Dept. of Meta and Mater Engg, NITK, Surathkal, Karnataka, India
c
Naval Physical and Oceanographic Laboratory, Kochi - 682021, Kerala, India
d
R & D Centre, Dept. of Mech. Engg., SIT, Tumkur-572103, Karnataka, India
e
Dept. of Mech. Engg., MMEC, Belgaum-591113, Karnataka, India
*
[email protected], [email protected], [email protected],
[email protected], [email protected], [email protected]
Keywords: Epoxy, Nano-alumina, Mechanical properties, Friction and wear, SEM
Abstract: In the present work systematic study has been conducted to investigate the matrix
properties by introducing nanosize Al2O3 (particle size 100 nm, 0.5–10 wt %) fillers into an epoxy
resin. High shear mixing process was employed to disperse the particles into the resin. The
experimental results indicated that frictional coefficient and wear rate of epoxy can be reduced at
rather low concentration of nano-Al2O3. The lowest specific wear rate 0.7 x 10-4 mm3/Nm is
observed for the composites with 1 wt.% which is decreased by 65% as compared to unfilled epoxy.
The reinforcement of Al2O3 particles leads to improved mechanical properties of the epoxy
composites. The results have been supplemented with scanning electron micrographs to help
understand the possible wear mechanisms.
Introduction
Polymer composites are widely used as structural materials in aerospace, automotive and
chemical industries, as they provide lower weight alternatives to metallic materials. Gears, cams,
bearings and seals are tribological components, where the self-lubrication properties of polymers
and polymer composites are of special advantage. The incorporation of well-dispersed nano- or
micro-sized inorganic particles into a polymer matrix has been demonstrated to be quite effective to
improve the tribological properties of the polymer composites [1-8]. It was verified experimentally
by numerous researchers that nanoparticles of metallic or inorganic type, prove the ability to
reinforce effectively thermoplastic and also thermosetting polymer matrices [10]. Specifically, the
reinforcement covers improvements of the flexural modulus without loosing flexural strength. This
effect is at the same time accompanied by improvements in fracture toughness and impact energy
which, however, depend strongly on the filler volume content [11]. However, the unique nanocomposite effects can only be effective, if the nanoparticles are well dispersed in the surrounding
polymer matrix. It has been shown that, a considerable improvement of the mechanical and
tribological properties can already be achieved at very low filler volume content, somewhere in the
range of 1–5 vol% [12–14].
Epoxies exhibit superior qualities such as high glass transition temperature (Tg), high modulus,
high creep resistance, low shrinkage at elevated temperature and good resistance to chemicals due
to their densely cross-linked structure. Having ability to adhere to a variety of fillers, they are used
for high-performance coatings for tanks and structures. There are special grades of epoxy for
elevated-temperature service to about 176◦C. In the present work, nano-Al2O3 filled epoxy
composites have been prepared by using high shear mixing process for particle dispersion. The
filler content was varied in the range 0.5-10 wt%. The effect of filler content on mechanical and
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
www.ttp.net. (ID: 27.251.8.22-15/07/14,11:59:19)
Applied Mechanics and Materials Vols. 592-594
1321
tribological properties of the nanocomposites has been studied. Epoxy nanocomposites containing
100 nm alumina particles have not been studied. Hence the present work is taken up.
Experimental Details:
Epoxy resin LY 556 (diglycidayl ether of bisphenol A) and hardener HY951 (triethylene
tetramine) were supplied by Huntsman Advanced Materials Pvt. Ltd (Mumbai, India). Al2O3
nanoparticles were purchased from Sigma Aldrich (Bangalore, India). Al2O3 represents the ceramic
nanocrystalline phase and consists of primary particles in the size of 100 nm. They have a specific
surface area of 100m2/g. The epoxy resin of known weight (g) was taken in a beaker. Al2O3
nanoparticles were added into the resin. The mixture was stirred using a homogenizer (Miccra D-9,
speed range of 11 000–39 000 rpm) for 2 h. The high shear mixing results in the separation of
particle agglomerates. The hardener (10 wt% of resin) was then added into the mixture and stirred
for 15 min. The mixture was then poured into the mould. Curing of the composite at 25°C for 24 h
and post-curing at 70°C for 1 h were carried out. Composites with filler contents of 0.5, 1, 5 and 10
wt.% were prepared. Flexural tests of pure epoxy resin and the composites were carried out in a
UNITEK 9450 PC universal testing machine in accordance with the ASTM D790 standard at a
deformation rate of 1 mm/min, while un-notched impact tests were conducted in a FIE IT-30 tester.
The hardness of the materials was measured using an FIE RASNB Rockwell hardness tester with
‘F’ scale (1/16” diameter ball indenter and 60 kg load). A loading time of 30 s was used.
Unlubricated pin-on-disc sliding wear tests were carried out in order to determine the
tribological properties of the nanocomposites. Sliding was performed in air with the ambient
temperature of around 25°C over a period of 60 min. at a sliding velocity of 0.84 m/s and a normal
pressure of 0.8 MPa. The test samples were accurately weighed before and after the wear run using
electronic balance (0.1 mg accuracy) to determine the wear loss. The friction coefficient was
calculated by taking into account the normal load and the friction force. The wear performance is
described by specific wear rate (Ks):
where ∆ m is the mass loss in grams (g), ρ is the measured density of the sample in (g /mm3), FN is
the normal load in (N) and L is the sliding distance in meters (m). The average of the three readings
was adapted in our results. Scanning electron microscopy examinations on a Jeol-5400 was used to
study the morphology of fracture surfaces from flexural testing and the morphology of worn
surfaces.
Results and Discussions
Mechanical Properties: Table 1 shows the mechanical properties of the composites containing
different concentrations of Al2O3. It is seen that the flexural and impact strengths of the composites
are increased by the addition of nano-Al2O3, with the highest values being obtained at composites
containing 0.5 wt% nano-Al2O3. Nanocomposites impart a high portion of interface. The increase in
flexural strength and modulus suggests that stresses are efficiently transferred via the interface.
However, the flexural and impact strengths of the composites are decreased with increasing nanoAl2O3 content above 0.5 wt.%. Thus, it can be inferred that a higher content of Al2O3 is unfavorable
for increasing the mechanical properties of the composites. On the other hand, it can also be see that
the hardness of the composite is almost unchanged with increasing Al2O3 content. This implies that
nano-Al2O3 may be ineffective for increasing the load carrying capacity of the composites
containing nano-Al2O3. The hardness of the composites is not only one factor to determine the
tribological behaviour of materials. The interfacial interaction between the epoxy matrix and the
nano-Al2O3 may be also an important factor.
1322
Dynamics of Machines and Mechanisms, Industrial Research
Tribological behaviour: In general, the friction and wear properties do always describe the whole
tribological system rather than a material property alone. Fig. 1a shows the specific wear rate (Ks)
of the nanocomposites as a function of content of Al2O3 nanoparticles. It was found that the nanoAl2O3/epoxy composites exhibited decreased Ks in comparison to the neat epoxy. The Ks sharply
decreased when nano particle content was below 1 wt%. 1 wt% nano-Al2O3/epoxy exhibited the
lowest Ks. Although, the Ks increased with increasing Al2O3 content above 1 wt. %, it was still
Table1. Shows mechanical properties of epoxy composites containing different concentrations of
nano-Al2O3
Flexural strength
Impact strength
Hardness
Nano-Al2O3
2
MPa
kJ/m
content wt.%
Kg/mm2
0
36.9
18.68
83
0.5
94.7
31.87
83.5
1
56.6
16.85
82.8
5
34.7
16.36
80.34
10
41.4
18.19
81.8
lower compared to the neat epoxy. 1 wt.% nano-Al2O3/epoxy composite showed the Ks value of
0.7x10-4 mm3/Nm (- 65%) compared to the neat resin’s value of 2.0 x 10-4 mm3/Nm. Rong et al. [9]
examined the influence of microstructure on the tribological performance of nanocomposites by
different compounding methods. They confirmed that the dispersion state of the nanoparticles and
micro-structural homogeneity of the fillers improve the wear resistance significantly. The
phenomenon reported in the present work is similar to the one reported by Rong et al [9]. Besides
improving the wear resistance, the nanoparticles also reduce the coefficient of friction as shown in
Fig. 1b. Evidently, the nano-composite with 1 wt% Al2O3 has the lowest friction coefficient. The
coefficient of friction decreases from 0.57 for unfilled epoxy to 0.44 at 1 wt%. The detached
nanoparticles might also act as solid lubricant. These account for the lower specific wear rates and
friction coefficients of the nanocomposites.
(a)
(b)
Fig. 1. (a) Specific wear rate of unfilled epoxy and nano-Al2O3/epoxy composites (Normal pressure,
0.8MPa; Sliding velocity, 0.84m/s; sliding distance, 3014m) (b) Friction coefficient of
unfilled epoxy and nano-Al2O3/epoxy composites.
Worn surface studies: The morphologies of the worn pins’ surfaces were examined by SEM at an
identical magnification of 500 X (Figs. 2a-c). The main features on the worn surface of the neat
epoxy are severe damage characterized by the disintegration of the top surface, wear debris and
Applied Mechanics and Materials Vols. 592-594
1323
deep grooves in the sliding direction (Fig. 2a). In the case of filled nanocomposites, the appearances
are completely different and become rather smooth. Although the ploughing grooves are still visible
on the sample surface, the groove depths are shallow on 1 wt% filled epoxy (Fig. 2b) and at some
region, the grooves are simply invisible. It seems the low filler loading is sufficient and can bring
about significant improvement in wear resistance. During sliding, a rolling effect of nanoparticles
could reduce the shear stress, the friction coefficient and the contact temperature. The matrix
damages in the interfacial region were reduced by this rolling effect. However, the wear resistance
suffers if the filler loading exceeds 1 wt% and the large amount of nanoparticles cannot provide any
wear reducing effect. Abrasive wear is accompanied by delamination and fatigue cracking of the
matrix (Fig. 2c).
(a)
(b)
(c)
Fig. 2. Micro-photographs showing worn surface features of (a) unfilled epoxy, (b) 1wt% Al2O3
/epoxy and (c) 5 wt% Al2O3/epoxy nanocomposites.
Conclusions
This study focused on the development of nanocomposites with properties superior to the neat
matrix. The following conclusions can be drawn:
1. The reinforcement of Al2O3 leads to improved mechanical properties. Mechanical properties
do not exert remarkable influence on the wear behaviour of the materials.
2. The optimum wear resistant composition was found to be 1 wt% Al2O3 which exhibited the
decrement in sp. wear rate of -65% (0.7x10-4 mm3/Nm) compared to the neat resin’s value
of 2.0 x 10-4 mm3/Nm. Microscopic observation of the worn surfaces indicate a positive
rolling effect of the debris between the sample and the counterface.
1324
Dynamics of Machines and Mechanisms, Industrial Research
3. Nano-Al2O3 filled epoxy composites show signs of mild abrasive wear due to the hard
ceramic particles. The main wear mechanism of the composite changed from the severe
abrasive wear (for neat epoxy matrix) to mild abrasive wear.
Acknowledgements
The authors thank Director Dr K.U. Bhaskar Rao, DMSRDE Kanpur for permitting to conduct the
present research work.
References
[1]Q. Wang, Q. Xue, W. Liu and W. Shen, Tribological properties of micron silicon carbide filled
poly (ether ether ketone), J. Appl. Polym. Sci., Vol. 74 (1999), p. 2611–2615.
[2]J.M. Durand, M.Vardavoulias and M. Jeandin, Role of reinforcing ceramic particles in the wear
behavior of polymer-based model composites, Wear, Vol. 181–183 (1995), p. 833–839.
[3]M.Q. Zhang, M.Z. Rong, S.L. Yu, B. Wetzel and K. Friedrich, Effect of particle surface
treatment on the tribological performance of epoxy based nanocomposites, Wear, Vol. 253
(2002), p. 1086–1093.
[4]J.-C. Lin, Compression and wear behavior of composites filled with various nanoparticles,
Compos. Part B – Eng., Vol. 38 (2007), p. 79–85.
[5]S. Bahadur and D. Gong, The role of copper compounds as fillers in the transfer and wear
behavior of polyetheretherketone, Wear, Vol. 154 (1992), p. 151–165.
[6]S. Bahadur and D. Gong, The investigation of the action of fillers by XPS studies of the transfer
films of PEEK and its composites containing CuS and CuF2, Wear, Vol. 160 (1993), p. 131–138.
[7]B.J. Briscoe, A.K. Pogosian and D. Tabor, The friction and wear of high density polythene: The
action of lead oxide and copper oxide fillers, Wear, Vol. 27 (1974), p. 19–34.
[8]N.V. Klaas, K. Marcus and C. Kellock, The tribological behaviour of glass filled
polytetrafluoroethylene, Tribol. Int. Vol. 38 (2005), p. 824–833.
[9] M.Z. Rong, M.Q. Zhang, H. Liu, H.M. Zeng, B. Wetzel and K. Friedrich, Microstructure and tribological
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Dynamics of Machines and Mechanisms, Industrial Research
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Mechanical and Tribological Behaviour of Epoxy Reinforced with Nano Al2O3 Particles
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