Mehoub 2013
Mehoub 2013
Mehoub 2013
Surveying
A dissertation submitted by
MR GABREL MEHOUB
00610123160
(Mechanical Engineering)
ii
Abstract
Friction and dry wear behaviour of glass fibre reinforced epoxy (GFRE) and glass
fibre reinforced polyester (GFRP) composites are studied in the current project.
Three sliding orientations of fibre with respect to the sliding distance are considered
and normal orientation (N-O). On the other hand, different sliding distances (0- 15)
km are accounted. The adhesive wear experiments were carried out using block-on-
ring (BOR) configuration at room temperature, applied load of (30N), and sliding
velocity of (2.8 m/s). Interface temperature and frictional force were captured and
recorded during the sliding. Worn surfaces were examined by using (SEM) to
classify the damage. The results revealed that the highest wear rate is taken place in
(AP-O) of GFRE. (P-O) is the highest wear rate of GFRP. On the other hand, the
lowest wear rate is exhibited for (N-O) at longer sliding distance. The maximum
friction coefficient is observed when sliding take place in (N-O and P-O) at higher
speed level. Although, (AP-O) shows 0.25 which is the lowest friction coefficient
value than other orientations. (P-O) orientation of GFRP gave higher wear rate at
iii
DISCLAIMER
Prof. S. Rain
Acting Dean
Certification
iv
I certify that the ideas, designs and experimental work, results, analyses and
conclusions set out in this dissertation are entirely my own work and effort, except
I further certify that the work is original and has not been previously submitted for
____________________________
Signature
____________________________
Date
v
Acknowledgements
This research project would not have been possible without the support of many
Yousif who was abundantly helpful and offered invaluable assistance, support and
guidance during the duration of my project. As a result, I felt more optimistic and so
creates extremely supportive and motivational area for study by providing their
equipment and facilities such as laboratories, library, software and qualified staff. I
am highly appreciated all my friends and their assistance in all the matters, especially
Abdulla Shalwan, for his time and enhanced me by creating significant assistances.
Last but not least, I wish to avail myself of this opportunity to express a sense of
gratitude and love to my beloved parents and whole family back home. Deepest
gratitude is also to my wife, and my son for their understanding and endless care
gratitude to my father who usually encourages me to provide the best and singular
form of advice.
Finally, special thanks also to the Libyan cultural attaché for their manual support,
strength, and help and for everything they have done for the good of me.
Gabrel Ahmad,
vi
TABLE OF CONTENTS
vii
CHAPTER4: RESULTS AND DISCUSSION .......................................................... 37
4.1 WEAR BEHAVIOUR .................................................................................. 37
CHAPTER 5: ............................................................................................................. 57
CONCLUSION AND RECOMMENDATION ......................................................... 57
5.1 CONCLUSIONS .............................................................................................. 57
5.2 RECOMMENDATION ................................................................................. 58
REFERENCES........................................................................................................... 59
viii
LIST OF FIGURES
Figure 2.1: Friction coefficient and specific wear rate of common ........................... 12
Figure 2.2: 1 Friction coefficient and Specific wear rate of common fibre polymer . 15
Figure 3.1: Micrographs of the original composites surface for a) GFRP and b)
GFRE 29
Figure 4.1: 1 Specific wear rate against sliding distance of GFRP and GFRE ......... 39
Figure 4.2: 1 Summary of the specific wear rate of the selected materials after
Figure 4.4: 1 Summary of the friction coefficient of the selected materials after
Figure 4.5: 1 Interface temperature vs. sliding distance the selected materials under
Figure 4.6: 1 Samples of the roughness profile of the selected materials at different
Figure 4.7: 1 Roughness value of the selected materials after test under 30 N applied
Figure 4.8: 1 Micrographs of GFRE worn surface after the test under 30 N applied
Figure 4.9: 1: Micrographs of GFRP worn surface after the test .............................. 54
ix
CHAPTER 1: INTRODUCTION
1.1 INTRODUCTION
As a result of the rapid development that the world witnesses and the challenge in
their competitive mechanical properties of high specific strength, low weight, low
are heavily used in many applications that have been determined for these
Tribological properties of such materials have been a core of interest for many
scholars and researchers. The friction and wear performance are the significance
bolts and nuts. On the other hand, Shalwan and Yousif (2013) have been
expounded that friction is the value of energy which dissipated at the material
contact surface. Wear, the resistance to remove of solid surface, has been defined
in various aspects such as weight loss, wear resistance and specific wear rate,
1
(Bajpai et al., 2013). Friction and wear are classified to become a main effect on
are mainly related to lifetime of the machinery, (Holmberg et al., 2012). In other
Nowadays, friction and wear are the most common problems that are encountered
the need to understand the tribological behaviour of polymer is clear of this fact of
polymer science and engineering (Brostow et al., 2010). There have been several
types of productive friction and wear such as brakes, clutches, bolts and nuts.
Also the unproductive friction and wear is equally considerable such as gas
turbine, cams and bearings, and external combustion engines, (Bhushan et al.,
addition, the authors have reported that friction comprises of three elements
namely, interfacial bonds, strength, and shearing and rupture of rubbing around
the contact area of materials. It may also lead to damage materials’ surface and
then change the mechanical properties of the composite. Finally, the results from
friction are temperature during converting mechanical energy to heat, this heat is
2
produced by friction and deformation of materials leads to generate heat. On the
other hand, few beneficial applications are provided by the friction such as tyres
There are several studies have been done to inspect the tribological performance
Carbone fibres were investigated by (Suresha and Kumar, 2009). From the
thermoset composites based on synthetic fibres such as glass. In the recent work
thermoset composites based on glass fibres. This motivates the current study.
In the current report, the wear and frictional behaviour of two fibre thermoset
fibre with respect to the sliding distance are accounted in the study and different
3
1.2 OBJECTIVES OF THIS STUDY
1. To study the specific wear rate and friction behaviour of epoxy and polyester
2. To study the influence of fibre orientations on specific wear rate and friction
coefficient.
3. To examine the worn surfaces of the composite after the test and categorize the
wear mechanism.
friction behaviour
the composite.
1. Understanding the wear behaviour of new materials will assist the designers in
3. The outcomes of the research will contribute to the tribological science and
will become a base for the new researches in this area. Furthermore, the
4
1.4 DISSERTATION LAYOUT
This dissertation organized for six parts as shown in figure 1.1 bellow. Firstly, the
it indicates the aims behind this project which substantially defines the activities
undertaken and the direction to complete this project. Secondly, the literature
review provides significant researches that have been reported in this area. These
articles reach to the damage that materials surface is subjected by different sliding
parameters; damage face in applicable materials is also focused such as epoxy and
polyester. Thirdly, the methodology demonstrates the equipment’s and the used
experiments' results and discussion are obtained in this chapter. Fifthly, the
5
Project Layout
Recent Works on
6
CHAPTER 2: LITERATURE REVIEW
sectors(Nosonovsky and Bhushan, 2012). Tribology is the Greek word ' tribo'
comprehends the science and technology that explore wear, lubrication, and
surface resulting of friction and wear, (Khonsari and Booser 2008). The
friction, wear, and other machine element such as piston rings, magnetic desk
Friction and wear, are the most common problems that encountered in industrial
and assemblies in engineering, (Unal et al., 2006). As a result, the use of polymer
surfaces. The author mentioned that there have been several types of productive
friction and wear such as brakes, clutches, bolts and nuts. Also the unproductive
7
friction and wear is equally considerable such as gas turbine, cams and bearings,
and external combustion engines. Moreover, Tooth wear studies have recently
of the real rubbing area, (van Kuilenburg et al., 2012). Other definition for friction
is the magnitude of energy that squandered at the material surface, (Shalwan and
Yousif, 2012). Based on the friction mechanisms which are namely severity
various aspects such as weight loss, wear resistance and specific wear rate,
(Hutchings, 1992). Bhushan (1995) highlighted that the energy resources in the
world have markedly appeared as friction in one model or/and more. In order to
to diminish the relationship strength between the natural fibre and polymer resin.
8
Yousif (2012) Notified that Friction, wear and lubrication are detected to
product quality.
contact adhesion measurement has been defined with different coatings of surface
executed under especial situations of dry sliding on the wear and friction
different factors which are sliding velocity, applied load, and temperature.
(Brostow et al., 2010). There are several structural applications which are
9
depended on polymer matrix. In addition, polymer and their composites have
Yousif (2008) highlighted that polymers and their composites are one of the
important materials used in the machine elements which are designed to avoid
tribological loading situations. Also the researcher has mentioned that the
has known under operational conditions such as friction and wear resistance. On
the other hand, tribological behaviour of polymeric composite has been paid
Blau (2010) has pointed out that the high-temperature; friction and wear are
propulsion systems. There have been two principal features that the polymers and
their composites was made to ensure that its characteristics meet technical
minimize such issues in the future. Hence, these materials has become desirable
10
(2008) has demonstrated that it also presupposes a preferable understanding of
sliding wear mechanisms as so to design parts which have friction and wear
Numerous studies of friction are shown that the main non-interacting components
2005), Fig. 2.1. Friction comprises of three elements namely, interfacial bonds,
strength, and shearing and rupture of rubbing around the contact area of materials,
(Myshkin et al., 2005). The wear resistance is considered as one of the significant
slipping contact, (Ben Cheikh Larbi et al., 2005). Also Cheikh Larbi, Cherif
(2005) mentioned that Variation of the surface layer obtained from the chemical
factors because of that particular structure and mechanical behaviour are acquired.
11
0.9 Friction cofficient 0.3
0.6 0.2
0.5
0.15
0.4
0.3 0.1
0.2
0.05
0.1
0 0
polyester[*] Epoxy[**] HDPE[***] PTFE[****]
Material Type
Drawing on obtained views, the polymers and their composites are prestigious
frictional loss between the layers of material. Based on the previous studies, the
required wear resistance and surface temperature were added to the technical
considerations.
12
2.2.1 TRIBOLOGY OF FIBRE POLYMER COMPOSITES
materials, (Shalwan and Yousif, 2012). From tribological point of view, the
increased and extending into even more new field. Many researches have been
carried out on the tribology of polymer due to their usage in several applications
Nowadays, polymer matrix composites are became the most attractive for many
impellers, brakes, clutches, conveyors, gears, cams, transmission belts, bushes and
abrasive wear by several studies, these results indicate that wear performance
Pihtili(2009) has reported that composites materials are widely used because of
their properties such as low density and cost. For the few decades, glass fibre is
kind of these materials; numerous studies have been allocated for these materials
elevated temperature. For instance, the sliding wear is caused to reduce the wear
13
resistance, for example in the case of adhesion and fatigue of wear. Moreover,
of the fibres. the results have provided that there is an existence remarkable
al., (2006) Investigated that the wear resistance of glass fibre reinforced polyester
composites have higher wear resistance compared to plain polyester. also there are
three contact direction which are parallel(P), anti-parallel (AP), and normal
Myshkin (2006) has presented that there have been other impacts on friction in
generated from friction and the main source of this heat is deteriorated of surface.
parameter. The author studied the deformation and adhesion of friction. This
research is shown the principles effects of applied load, sliding velocity, and
temperature. Hence, In the light of this weight, the applied load specified
14
2.2.2 Adhesive Wear Behaviour Of Fibre Polymer Composites
surface forces were formed of attraction and repulsion distribute between the
molecules and atoms of two approaching surfaces. These forces equalize each
other, (Myshkin et al., 2005), Fig. 2.2. Likewise, Myshkin, Petrokovets et (2005)
molecular forces, which are effectively between two solids with particular agents.
Friction
Coefficient(µ)
0.3 specific wear rate 8
7
0.25
6
0.2
5
0.15 4
3
0.1
2
0.05
1
0 0
G/P[*] G/E,P-O[**]
C/Viny[***]
G/Viny[***]
Material Type
Fig. 2. 2 Friction coefficient and Specific wear rate of common fibre polymer
composites, [*](El-Tayeb et al., 2008), [**](Pihtili, 2009), [***](Suresha and
Kumar, 2009).
15
Adhesion and deformation are measured the source of frictional forces. Therefore,
deformation appears while two slides surface contact to each other, such as plastic
and applied load are proportional to friction force, at load between 10-100
maximize and at high velocity. Finally, the results from friction are temperature
during converting mechanical energy to heat, this heat is produced by friction and
According to the tribological of view, there have been implemented several works
on jute, cotton, oil, palm, sugarcane, coir, and bamboo fibres concerning their
reinforced polyester composite is detected that oil palm fibres reinforced the wear
with the addendum of cotton fibre. Furthermore, sugarcane fibre has been
parallel to the sliding direction presented that wear performance of fibre mats
oriented parallel to the sliding direction is lower than fibres oriented anti-parallel
16
The influences of the coir fibres can be measured in terms of frictional and wear
microscope wear rate and friction coefficient were studied in various aspects
which are applied load between 10N to 100N, and sliding distance between 0km
It is generally accepted that the adhesive wear behaviour of polymers has been
affected by several issues such as high friction of coefficient, stick slip behaviour,
and high material removal. Therefore, many authors have reported that the most
interfacial adhesion of the fibre with the matrix is considered as one of several
enhanced by reducing the wear rate in glass fibres. Moreover, the performance of
wear and frictional relies on some parameters which are applied load, sliding
controlling the wear and the frictional behaviour of composites, (Chauhan et al.,
polyester composites have been studied by Yousif and El-Tayeb (2010). Also the
17
researcher has explained that high micro and macro crack diffusion on the
interface of the composite surfaces. However, the shear force is resisted and
managed by the end of the fibres to protect the polyester area. The large diameter
is the main reason that it can be caused to disseminate of crack whether micro
conditions, which are wet and dry. From the previously reported, some of
polymeric composites such as PA, UHMWPE, (Suresha et al., 2009), and betelnut
fibres, (Nirmal et al., 2010a), have been enhanced during wet contact conditions
compared to dry. Many researchers have been explored the effect of adhesion of
elastic. Whereas, the elastic half-space comes in contact with a smooth sphere the
friction comprises strong long-range bulk forces, and weak short-range adhesive
forces. To sum up, the adhesive friction includes the technicality of energy
Throughout history, friction has been defiance for humanness. Hence, Myshkin
and Petrokovets (2006) defined that friction is the resistance of motion contact
between thin surface layers of bodies which the fundamental way for heat transfer
18
between tribology is caused by friction and concept of convection. Friction is the
magnitude of energy that consumed at the surface. Frictional behaviour has been
have been attributable to frictional behaviour which is adhesion and blouging, and
cruelty deformation. Also, researchers have made attempts to determine that the
that, the behaviour of these mechanisms depends on operating conditions and the
type of material which are namely the contact surface topography, (Shalwan and
Yousif, 2012).
adhesion, fracture and third body mechanisms. Based on these studies, the
theoretical rules to measure the coefficient of friction are the equal normal load to
the ratio of the friction force. In the light of this weight, Suresha, and Shiva
results shows that the coefficient of friction is directly proportional to applied load
and/or sliding velocity. Shalwan and Yousif (2012) have applied an experiment
to measure the friction behaviour of the natural fibres under dry sliding
provisions; the authors reported that the frictional coefficient of epoxy is reduced
by the existence of kenaf fibres in the composites. Also polyester with coir and
19
betelnut and oil palm fibres achieve respectively reduction of the friction
coefficient.
Diverse works have focused on volume friction behaviour of natural fibres. These
can be strongly influenced by the volume friction, Yousif and El-Tayeb (2008a)
have explored that the effort of replacing seed oil palm fibres(SOPF) with woven
have been done under dry sliding contact by using (BOD) with special conditions
which are sliding distances up to 5 km, applied load 20N, and sliding velocity 2.8
m/s. In addition, Chin and Yousif (2009) have pointed out that kenaf fibres as
reinforced with epoxy matrix have been used for bearing applications.
distances up to 5 km, sliding velocities (1.1-3.9 m/s). Kenaf fibres afford greater
wear and friction coefficient as support to the matrix compared to oil palm, coir
fibres, and sugarcane. Subsequently, set of results are exposed that the specific
wear rate (ws) of woven glass reinforced polyester (GRP) and 35% volume of
seed oil palm reinforced polyester (SOPRP) were comparable, (Yousif and El-
Tayeb, 2008a). The study also provided that the applied load and sliding velocity
have sparse influence on the KFRE composites. However, the fibre orientation
20
has obviously affected on the frictional behaviour and wear performance of the
tribology and materials sector. Yet, there remains an argument whether the
applications. For instance, in the USA, reducing friction in engine parts has
economized 120$ billion per year, (Yan et al., 2010). Advantageous, friction has
used for everyday applications such as tyres, brakes friction. On the other hand,
shear force and heat generation are occasionally caused by friction between
passenger cars, tires, and breaks. Friction, lubrication, and wear have been
21
applications such as internal combustion engines, bearing of aerospace propulsion
Moreover, different properties are caused due to the increase of temperature such
alloys yield strength has progressively decreased after critical point of yield
strength such as nickel alloys, (Blau, 2010). Also, the researcher has studied the
diameter. From the experiment's results the author has proved that high
There are many influences of interface temperature on the wear and frictional
behaviour. Pihtili (2009) has investigated that the wear of glass-woven reinforced
under dry conditions. The previous works focus on the polymeric composite
material in terms of the wear and friction properties. low thermal conductivity
and high stiffness have been specified under particular conditions which are high
temperature at the sliding surfaces meanwhile friction and after a specific critical
(Pihtili, 2009).
22
Several experimental have been done by Yousif and El-Tayeb (2008b) to
fiberglass reinforced polyester (CGRP). The researchers have used three various
orientations, namely parallel (P), anti-parallel (AP) and normal orientation (N).
Also they are several parameters, namely normal load (30, 60&90), sliding
velocity (2.8, 3.52 & 3.9 m/s), and sliding distance (0-2.51km). Experimental
CGRP/stainless steel based on principal roles which are pattern's orientations, and
the tested parameters. The result from measurements, which proposed by the
researchers, were exhibited that the interface temperature of (AP & P) orientation
AP-orientation during higher friction rates, and however, the interface temperature
mechanism.
metals and their wear resistance which are connected to oxidation, sulfidation, and
kinetics. As a result, the Ellingham diagrams are used to measure the change of
the Gibbes free energy (G) by comparing with function of temperature which is
23
rates are inclined to increase while temperature increases. Furthermore, Blau
layers during frictional contact. Temperature resulting can be specified as the sum
such as bearings, bushings and sliding surfaces. However, these materials are
subjected to deterioration due to heat generated by the friction and/or shear force
as Jute, Cotton, Oil palm, Sisal, and Kenaf. Eventually, the interface temperature
compared to the frictional force. Furthermore, the friction and wear behaviour of
the polymeric composites are controlled by equal operating parameters and fibre
24
2.3 Recent works on synthetic fibre polymer composites
Synthetic fibres have brought more sufficient as advanced composites and
applications have been heavily studied. The petroleum issues have made bio
research, (Faruk et al., 2012). Synthetic fibres have several features compared to
There are immense works on Synthetic fibres polymer composites focusing on the
previous works are addressed covering the mechanical and tribological researches
on such composites.
clarify different studies under different sliding parameters. The literature review
can publicize obvious explanations of previous researches or/and studies that have
parameters. For example, (Yousif et al., 2006), have studied interface temperature
and friction coefficient of glass fibre/polyester under different applied loads and
25
different sliding distance. They found the interface temperature approximately
24-48 ºC and the increase of friction coefficient is discovered between the glass
fibre and the polyester. According to these previous works different surface
damage features are resulted from experiments under different sliding conditions.
No much researches concentrated on the study between the friction force and wear
resistance with surface observations. This research will study the influences of
friction force, specific wear rate, and interface temperature on the surface damage
by tribological loading.
26
CHAPTER 3: METHODOLOG
This study proposed to use these materials in terms of their surface damage
conditions. Hence these materials have to be used in these experiments easier than
other materials which may appear no surface damage. This project has used well
known materials such as Neat Epoxy (NE), Glass Fibre Reinforced Epoxy
(GFRE).
characteristic. In addition, this work has been used the liquid of epoxy resin (DER
331). It is occasionally used for several purposes such as automotive parts and
casting. Epoxy resin supplies good resistance to adhesive and alkalis properties.
The epoxy resin and hardener has been mixed with 2:1 of ratio. Also the mixture
was systematically made, melted down in the mould and placed in the vacuum
room (MCP 004PLC). In order to dispose of air bubbles between fibres in the
mould at room temperature 24 hour. Glass fibre reinforced epoxy and glass fibre
prestigious properties for, this specimens were conducted with the specific
27
fibre have been paid attention. GFRP were used as a reinforcement material that it
high melting solids, and viscous liquids. They have numerous of mechanical
less than 2% of the shrinkage and high hardness. The provided composites were
displayed in Fig.3.2.
28
Glass fibre
Polyester
b) GFRP
a) GFRE
29
Fig. 3. 2 Schematic drawing showing the orientation of the fibre
that has been used a. Glass fibre reinforced polyester has been produced under a
(MEKP) which can be used for ambient the surrounding temperature. Kong Tat
30
3.2 EXPERIMENTAL SET UP
Block-On-Ring (BOR) is the main machine that it has been used to conduct the
Before each test, (Sic G2000) was utilized to smooth the counterface and
thereafter a piece of wet cloth with acetone was used to clean the counterface. Fig.
3 shows the block on ring step up showing the load cell, samples, counterface and
the sample holder. The load cell is connected to the computer to capture the
The roughness of the wear track was gauged before and after experiment by using
Mahr Perthometer S2, As a result for higher close contact between the stainless
31
steel and the specimen, abrasive paper (Sic G2000) and dry soft brush was used to
polish and cleaned respectively the specimens contact surface. The composite
surface varies in each orientation in terms of the roughness. For instance, in N-O,
the composite roughness measures were in rate of the (0.70µm). While, in P-and
sliding distance. Before and after the test, the dry soft brush cleaned the prepared
this operation to determine and ensure the weights of the composite specimen
before and after test and then weight loss was evaluated. In addition, thermo-
SEM (JEOL) was used to investigate the composite surface morphology. The
composite specimen surface was coated before to use the SEM machine. Thus,
each tribological test was repeatedly done several times and the average of the
magnitudes was measured. The weights of the specimens before and after test
using Sera balancer and then specific wear rate were determined for each test
(1)
32
In the light of this weight, during and after the experiment interface temperature
was standardized. Using a thermo imager can be used while after the test, can
also show the heat allocation during the materials sample. Moreover, the
temperature was generated and the thermo imager camera has been used because
of interface temperature was calibrated during periods of time. The specific wear
performance is one of the expected results as so to explore the impact of the wear
measure the relationship between the sliding distance and the weight of the
specimen before and after the test in order to investigate the specific wear rate.
As a result the required friction force can be obtained by the tribology software
which was connected with the Block-on-Ring machine. Hence, shear force
In the light of this weight, during and after the experiment interface temperature
was standardized. Using a thermo imager can be used while after the test, can
also show the heat allocation during the materials sample. Moreover, the
temperature was generated and the thermo imager camera has been used because
33
3.2.3 SPECIFIC WEAR RATE AND FRICTION FORCE READINGS
The specific wear performance is one of the expected results as so to explore the
impact of the wear damage on the specimen surface. Therefore, theoretical rules
were applied to measure the relationship between the sliding distance and the
weight of the specimen before and after the test in order to investigate the specific
wear rate. As a result the required friction force can be obtained by the tribology
software which was connected with the Block-on-Ring machine. Hence, shear
There are different surface procedures in order to obtain the required outcomes
Queensland (USQ).
supplied the generality of this equipment. As a result, the valid and accurate
34
3.2.5 MAHR PERTHOMETER
The roughness of the surface is important parameters that can be measured before
the test by using this tool. Moreover, Mahr Perthometer can be used in every
single test for every specimen to avoid any possible error during the experiments.
features; however, this equipment is not able to present results in micro. On the
35
3.6.4 DEMONSTRATE THE THERMAL-IMAGER
accurate results that might provide from infrared thermometer. Based on heat
distribution in the specimen some of random samples of images has been attached
According to previous studies, sliding conditions have been chosen due to the
surface damage was showed. Therefore, this study will attempt to use these
36
CHAPTER4: RESULTS AND DISCUSSION
behaviour of the composites and the thermoset are introduced in a form of friction
coefficient, interface temperature, and specific wear rate. Surface morphology and
roughness profile of the worn surfaces are given to assist in explaining the
In order to study the wear behaviour of neat epoxy, (NE), neat polyester (NP), glass
fibre reinforced epoxy (GFRE) and glass fibre reinforced polyester (GFRP), a series
The specific wear rate of the GFRE and NE against the sliding distance of different
orientations is given in Fig. 4.1.a. Since the specific wear rate (SWR) value of all the
selected materials is very small, the presented values are multiplied by 1000000, and
i.e. the values should be multiplied by E-6. Moreover, the specific wear rate of the
epoxy is relatively high compared to its composites that are why its values are on the
right vertical axis with different scale. From this figure, one can see that the neat
epoxy exhibits very high specific wear rate and reached the steady state after about 5
37
km. on the other hand, the epoxy composites show lower specific wear rate
compared to the neat epoxy for all the fibre orientations. The steady state of the
composites reached after about 10 km since the interaction between the asperities
took longer time to adopt. Further explanation will be given with the assist of the
Regarding to the composite, (AP-O) orientation indicates poorly wear rate compared
to (P-O) and (N-O) orientations, the composite in (P-O) and (N-O) directions exhibit
lower wear rate after sliding distance of 5 km. moreover, in comparison with Neat
epoxy and three orientations found that AP- orientation has approximately 30% less
than Neat epoxy while (P-O) and (N-O) orientations give about (20% less). The
realization for this can be explained that the proportionally harder phase (CSM) is
pulled out, broken, fractured of glass fibres and removed from CSM. It is generally
accepted that the weight loss of the composite specimens have significantly increased
with the effect of constant sliding velocity and sliding distance when applied load
was about 30 N.
38
GFRE-NO
0.07 GFRE-AP 0.25
GFRE-P
0.06 Neat Epoxy
0.2
SWR, mm3/N.m E-6
0.04 0.15
0.03 0.1
0.02
0.05
0.01
0 0
0 5 10 15 20
Sliding distrance, km
a) GFRE
0.5 0.5
0.45 0.45
0.4 NEAT P 0.4
GFRP N-O
0.35 0.35
SWR, mm3/N.m 10 -6
GFRP-AP-O
0.3 GFRP P-O 0.3
0.25 0.25
0.2 0.2
0.15 0.15
0.1 0.1
0.05 0.05
0 0
0 5 10 15 20
Sliding distance,km
a) GFRP
Fig. 4. 1 Specific wear rate against sliding distance of neat polyester, neat epoxy,
and GFRP and GFRE composites
39
The result of specific wear rate of glass/polyester and neat polyester against the
specific wear rate of glass/polyester at various orientations with the neat polyester.
Since the highest wear rate value is registered for the (P-O) at sliding distance of
about 3 km since the interaction between the hardness some time to adopt, the right
vertical axis is presented the values of specific wear rate. Because the specific wear
rate (SWR) is very small, the obtained values are multiplied by 1000000. It is
generally seen that the polyester composites show the lowest specific wear rate for
(AP-O and N-O) at approximately after 3 km. Likewise, the composites reached the
steady state after 6 km. Concerning to the composite, the wear rate has significantly
decreased with increasing the sliding distance for the orientations, i.e. (AP-O and N-
O) This lowering is pronounced after about 3 km. After about 6 km all the
composites have reach the steady state. Meanwhile, for (N-O) gives less wear rate
compared to the others for all levels of sliding distances are tested. Furthermore,
there is no markedly difference in wear rate for all the composites when they reached
the steady state. Differently, in comparison with (N- O) exhibits less wear rate at
lower sliding direction and slightly decrease in wear rate at higher sliding distance.
It is accepted that glass fibre gives superior wear performance and through the
sliding of the (N-O) orientation. (Ws) Values of the composites are obviously
decreased as a result the better wear behaviour of the composite is achieved for (N-
between the glass fibre and the polyester resin. From the mechanical point of view,
hus the material’s strengthens is another reason hich can cause to lo er eight
40
removal. However, Summary of the specific wear rate of the selected materials after
reaching the steady state at 10 km is shown in Fig.4.2. It seems that there is general
value of specific wear rate of GFRE and GFRP in which the best wear performance
can be achieved, i.e. (N-O) for both fibre composites exhibited an optimum value.
On the other hand, neat epoxy and neat polyester are reached the highest value for
both composite. GFRP is shown the higher value compared to GFRE in the case of
(AP-O). Moreover, there is markedly difference value between the composites in (P-
O). However, the optimum wear value is produced in the (N-O) for both materials.
Due to the lowering in the hardness of the film in the composite surface this can be
0.07 0.06
0.06 0.05
GFRP GFRE
Ws,mm³/N.m 10 -6
0.05
0.04
0.04
0.03
0.03
0.02
0.02
0.01 0.01
0 0
NEAT N-O P-O AP-O
Materials' Orientations
Fig. 4. 2 Summary of the specific wear rate of the selected materials after reaching
the steady state.
41
4.2 FRICTION COEFFICIENT
Fig 4.3.a shows the distinction of friction coefficient values for all materials with
sliding distance for three orientations and applied load 30N, and sliding velocity
2.8m/s. It can be indicated that the trend of the friction coefficient is slightly
decreased with increasing the sliding distance for the neat epoxy. Moreover, friction
and starts to reach a steady state. Differently, anti-parallel orientation provides the
lowest value of friction coefficient comparing to neat epoxy (about 29% lass). As a
result, the values of friction coefficient have evidently increased for the most
orientations. The glass fibre epoxy composite confirms that similar behaviour to
three orientations. However, the friction coefficient of the composite with fibres is
higher than the glass fibre where glass fibre demonstrates about the range of 0.29 to
0.45 while the neat epoxy gives above 0.49 of friction coefficient.
In the light of this, there is difference between the three orientations of the composite
in terms of friction coefficient. It can be seen that there are close values for the
friction coefficient between normal and parallel, however, the trend of the anti-
parallel orientation exhibits the lowest value of (0.25-0.3) than the others.
The effect of sliding distance and applied load on friction coefficient of GFRP is
presented in Fig 4.3.b. In addition to that, the influence of glass fibres on the
tribological behaviour of the neat polyester and the composite are clarified.
42
Regarding to the composite, the findings of friction coefficient are provided as a
function of sliding distance at 30N applied load. Generally, it can be seen that the
km) sliding distance. However, it appears that normal and anti-parallel (N-O and
AP-O) orientations have achieved the lowest friction coefficient at the applied load
of 30N which are about 0.23 and 0.28 respectively. Consequently, the higher value
of friction coefficient is evident for the neat polyester, which is about 0.42 while the
glass fibre composite at different orientations exhibit 0.2 to 0.3 of friction coefficient.
It can be seen that friction coefficient does not reach steady state at all sliding
distance increasing. This cause can be due to the strongly transfer film on the
counterface and the existence of the fibres and polyester. During longer sliding may
lead to impairs the adhesion between the two sliding surfaces and then associated
interaction takes place between them. The influence of the friction coefficient and
composite's worn surface. With regards to the glass fibre polymer composite, the
friction coefficient of both GFRP and GFRE are summarised in Fig 4.4. The highest
composite. However, the friction coefficient is high for other direction of the
composite. This can be noted that the deponding of fibre and the strong of interfacial
adhesion are avoided breakage and bending. As a result, (AP-O) show the lowest
friction value for both materials. Whereas, (N-O) in GFRE has a higher value than
43
(N-O) in GFRP. However, (AP-O) in GFRP is achieved the lowest value compared
44
a) GFRE
b) GFRP
45
0.6 0.6
GFRP GFRE
0.4 0.4
0.3 0.3
0.2 0.2
0.1 0.1
0 0
NEAT N-O P-O AP-O
Materials's Orientations
AP-O) and the comparison with the neat epoxy composite. The friction coefficient,
applied load and sliding distance are maximised. As a result, interface temperature is
expected that it is likely to increase. There is intimate relation between the interface
reaches gradually the high temperature when the sliding distance increases. it can be
46
noted that there is linear trend of temperature at the beginning of the sliding distance
until approximately 5Km, the highest degree is about 50ºC, after 14 Km for (NE).
Meanwhile, in the case of (AP-O) and (N-O), there is no severe effect on the
temperature degrees compared with (P-O) which reached 47ºC after 12km. Several
experiments have indicated that temperature trend is elevated gradually when the
sliding distance has long term effect on the composite. However, these outcomes
have been gained with the assist of thermo-imager camera which has been used for
every separate experiment at 30 N applied load, 2.8 m/s sliding velocity. Meanwhile,
the GFRE (N-orientation) is examined at 2.8 m/s, increasing in the sliding distance
does not observe any change in the temperature from 10 km until 14km.
Fig 4.5.b shows the maximum interface temperature that is evaluated during the
rubbing, i.e. at sliding distance 15km at 30N. The highest interface temperature is
measured due to the high friction coefficient of NP and GFRP (in P-O); higher
the lower temperature value than GFRE (in AP-O). Generally, the sliding distance
has close relation with the interface temperature, and friction coefficient of the entire
composite are increased. Therefore, we can record that the temperature starts in
increase after 10 km. Finally, thermo-image camera has been applied for every test
47
60
GFRE,N 30N
50 GFRE,APO 30N
GFRE, PO 30N
Temperature C 40 NE,30N
30
20
10
0
0 2 4 6 8 10 12 14 16
Sliding distance,km
a) GFRE
60
GFRP,N-O
50 GFRP,AP-O
GFRP,P-O
NP
Temperature,C
40
30
20
10
0
0 2 4 6 8 10 12 14 16
Sliding distance,km
b) GFRP
Fig. 4. 5 Interface temperature vs. sliding distance the selected materials under 30
N applied load
Further explanation will be exhibited with the assist of the roughness profile in the
next dictation. The results from the test are recorded in the direction of the
counterface and against the direction of the counterface. Fig 4.6 shows some samples
48
of the roughness profile of the selected materials GFRE/GFRP at different operating
parameters. On the other hand, Fig 4.7 summarises the roughness values of the
selected materials after test under 30 N applied load for 15 km sliding distance. Fig
4.7.a shows the roughness value of GFRE. It seems that the highest value is recorded
in the case of (AP-O) in the direction of the counterface while the lowest value is
provided in (P-O). Compared to the GFRE, Fig 4.7.b shows significantly reduce the
roughness value of the GFRP in (AP-O) for both directions; moreover, one can
notice that (P-O) shows less effect value on the counterface in the direction of the
counterface.
Regarding to the surface roughness profile of the neat polyester and GFRP in three
orientations, it seems that the roughness profile of the (N-O) orientation has reached
the highest value of roughness profile of 3.536m. However, the roughness profile of
the AP-O is the lower value. Fig 4.7.b shows the relation between the roughness
values of the GFRP after test under 30N applied load for 15 sliding distance. In
addition to that, the roughness profile of the neat polyester is slightly decrease
compared to the surface roughness profile of the neat epoxy in the previous section.
49
Fig. 4. 6 Samples of the roughness profile of the selected materials at different
operating parameters
50
Fig 4.8 shows the effect of the sliding distance on the worn surface of the GFRE and
GFRP composites. Concerning the composite, severe damage on the worn surface of
the GFRE (N-O) is recorded. At the maximum value of the sliding distance the
rubbing is partially different compared with lower distance. In order to reduce the
friction coefficient, a set of fibre has been removed and peeled off from the rubbing
micro-cracks have risen on the surface, indicate the elevated wear performance of the
conditions of higher load and/or sliding distance micro-cracks dominate on the wear
51
a) GFRE
b) GFRP
Fig. 4. 7 Roughness value of the selected materials after test under 30 N applied
load for 10 15km sliding distance
52
Fibre end
Depondi
ng
Micro-crack
Debris
Fig. 4. 8 Micrographs of GFRE worn surface after the test under 30 N applied
load in N-Orientation
53
Fig 4.9 represents that micrograph of GFRP worn surface after the test under 30 N
end is between the fibre and the resin zone. This concludes that (at sliding
distance) the wear mechanism of GFRP in N-O is dominated which related with
Fibre end
Plastic
Deformation
Fig. 4. 9 Micrographs of GFRP worn surface after the test under 30 N applied
load in AP-Orientation
54
4.5. Discussions and Comparison with Previous Published Works
In this chapter, the experimental results on neat epoxy, glass fibre reinforced
compared with some of the studies in terms of weight loss and frictional behaviour at
various operating parameters. Fig 4.10 presents several researches and studies that
have determined the values of specific wear rate and frictional behaviour of several
composites, and current outputs are painted of different colour. Shi et al., (2003)
have investigated the highest value of specific wear rate of neat epoxy composite
compared to the specific wear rate of this work (Shi et al., 2003). Furthermore, neat
polyester has marked the lower friction coefficient and weight loss, specific wear rate
and friction coefficient were measured about (0.03234), and (0.23) respectively, (El-
Tayeb, 2008). Moreover, the present specific wear rate of glass fibre/epoxy shows
the lowest value and the highest friction coefficient is recorded than the other one
which was studied by Pihtili (2009)(Pihtili, 2009). The friction coefficient and wear
rate of glass fibre/polyester composite are shown in figure below. The same friction
coefficient is produced compared to the value was defined by Shalwan and Yousif
(2012) (Yousif, 2012). However, glass fibre/polyester exhibits low specific wear
rate (0.02).
55
Fig. 4. 10 Specific wear rate and frictional behaviour of several composites,
(El-Tayeb et al., 2008)*,(Shi et al., 2003)**,(Pihtili, 2009)x,(Suresha and Kumar,
2009)xx
56
CHAPTER 5:
5.1 CONCLUSIONS
Few points are concluded as follows:
1. Presence of fibres and oriented have a significant influence on the wear and
reinforced epoxy composite, the better wear and frictional behaviour were
2. The fibre orientations has highly influence and similar in controlling the
friction and wear performance. However, the specific wear rate of the
the composites. Moreover, the sliding distance and applied load have a little
3. The detachment and breakage of fibres were the most effect on the wear
4. The worn surface of the composite showed different wear mechanisms. For
the GFRP, plastic deformation was clear and softening process occurred
during the sliding which deteriorates the composite surface. For the GFRE,
57
this less damage on the surface with the presence of the micro-cracks which
5. even though, the increasing temperature and frictional force have a substantial
the frictional force on the material removal from the composite surface.
the temperature can be resulted by the heat generated by the frictional force.
5.2 RECOMMENDATION
It is suggested that more researches have to be done on other type of materials in
order to evince and reach the existing work returns. While the tribology is the
interaction between different responses to the polymers, metals are preferred due to
consideration so as to reduce the friction force of the glass fibre based on epoxy
and/or polyester composites. Therefore, the high friction coefficient of the glass fibre
58
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63
APPENDIX A: PROJECT SPECIFICATION
PROJECT SPECIFICATION
1. To study the specific wear rate and friction behaviour of epoxy and
64
Project Synopsis:
There are many troubles in the field of industries. It is known that the friction is the
major pronounce resulting from the motion of contacted surface; therefore, high
temperature and shear force are generated in the rubbing area. Friction and dry wear
behaviour of glass fibre reinforced epoxy (GFRE) and glass fibre reinforced
polyester (GFRP) composites will be studied in the current project. The adhesive
room temperature, applied load of (30N), and sliding velocity of (2.8 m/s). Interface
temperature and frictional force will be captured and recorded during the sliding.
65
APPENDIX B: CONFERENCE PAPER
Abstract
Friction and dry wear behaviour of glass fibre reinforced epoxy (GFRE) and glass fibre
reinforced polyester (GFRP) composites are studied in the current project. Three sliding
orientations of fibre with respect to the sliding distance are considered in the investigation,
i.e. parallel orientation (P-O), anti-parallel orientation (AP-O), and normal orientation (N-
O). On the other hand, different sliding distances 0- 15 km are accounted. The adhesive
wear experiments were carried out using block-on-ring (BOR) configuration at room
temperature, applied load of 30N, and sliding velocity of 2.8 m/s. Interface temperature and
frictional force were captured and recorded during the sliding. Worn surfaces were
examined by using (SEM) to classify the damage. The results revealed that the highest wear
rate is taken place in (AP-O) of GFRE. (P-O) is the highest wear rate of GFRP. On the other
hand, the lowest wear rate is exhibited for (N-O) at longer sliding distance. The maximum
friction coefficient is observed when sliding take place in N-O and P-O at higher speed
level. Although, AP-O shows 0.25 which is the lowest friction coefficient value than other
orientations. (P-O) orientation of GFRP gave higher wear rate at maximum speed test in
comparing to normal orientation.
Keywords: Adhesive wear, Thermoset, Fibre, orientation
1. Introduction have taken place by several researches,(Yousif,
As a result of the rapid development that the world 2013b, Bajpai et al., 2013) focusing on the composite
witnesses and the challenge in using metal materials application in brakes, clutches, bolts and nuts. On the
in tribological industrial applications, the tribological other hand, Shalwan and Yousif (2013) have been
behaviour of polymeric composites has recently expounded that friction is the value of energy which
experienced a create development, and attention by dissipated at the material contact surface. Wear, the
many researchers. Fibre reinforced polymeric resistance to remove of solid surface, has been
composites have numerous advantages compared to defined in various aspects such as weight loss, wear
the metal materials due to their competitive resistance and specific wear rate, (Bajpai et al.,
mechanical properties of high specific strength, low 2013). Friction and wear are classified to become a
weight, low cost of raw materials, low processing main effect on the machinery in the field of industry
cost…etc. Recently, composites materials are heavily as so to work efficiently. Such deficiencies are
used in many applications that have been determined mainly related to lifetime of the machinery,
for these materials. Furthermore, composites (Holmberg et al., 2012). In other words, it is
materials have been provided superlative solutions to important to arouse many researches to study the
produce structural materials of aerospace industries, tribological behaviour of polymeric composites.
(Pihtili, 2009). Tribological properties of such Nowadays, friction and wear are the most common
materials have been a core of interest for many problems that encountered in industrial engineering
scholars and researchers. The friction and wear and machine parts which causes to the replacement of
performance are the significance characteristics that components and assemblies in engineering, (Unal et
66
al., 2004). As a result, the uses of polymer materials composites materials have been provided superlative
have been increased by industrial countries. solutions to produce structural materials of aerospace
Therefore, the need to understand the tribological industries, (Pihtili, 2009). Tribological properties of
behaviour of polymer is clear of this fact of polymer such materials have been a core of interest for many
science and engineering, (Brostow et al., 2010). scholars and researchers. The friction and wear
There have been several types of productive friction performance are the significance characteristics that
and wear such as brakes, clutches, bolts and nuts. have taken place by several researches,(Yousif,
Also the unproductive friction and wear is equally 2013b, Bajpai et al., 2013) focusing on the composite
considerable such as gas turbine, cams and bearings, application in brakes, clutches, bolts and nuts. On the
and external combustion engines, (Bhushan et al., other hand, Shalwan and Yousif (2013) have been
1995). Nevertheless, the influences of deformation expounded that friction is the value of energy which
and adhesion of friction are addressed. Friction on dissipated at the material contact surface. Wear, the
surface energy is affected by different factors which resistance to remove of solid surface, has been
are sliding velocity, applied load, and temperature, defined in various aspects such as weight loss, wear
(Myshkin et al., 2005). In addition, the authors have resistance and specific wear rate, (Bajpai et al.,
reported that friction comprises of three elements 2013). Friction and wear are classified to become a
namely, interfacial bonds, strength, and shearing and main effect on the machinery in the field of industry
rupture of rubbing around the contact area of as so to work efficiently. Such deficiencies are
materials. It may also lead to damage materials’ mainly related to lifetime of the machinery,
surface and then change the mechanical properties of (Holmberg et al., 2012). In other words, it is
the composite. Finally, the results from friction are important to arouse many researches to study the
temperature during converting mechanical energy to tribological behaviour of polymeric composites.
heat, this heat is produced by friction and Nowadays, friction and wear are the most common
deformation of materials leads to generate heat. On problems that encountered in industrial engineering
the other hand, few beneficial applications are and machine parts which causes to the replacement of
provided by the friction such as tyres, and brakes components and assemblies in engineering, (Unal et
friction. There are several studies have been done to al., 2004). As a result, the uses of polymer materials
inspect the tribological performance of polymeric have been increased by industrial countries.
composites based on synthetic fibres such as glass, Therefore, the need to understand the tribological
(Pihtili, 2009). Carbone fibres were investigated by behaviour of polymer is clear of this fact of polymer
(Suresha and Kumar, 2009). From the literature, there science and engineering, (Brostow et al., 2010).
is a lack of understanding on the tribological There have been several types of productive friction
behaviour of thermoset composites based on and wear such as brakes, clutches, bolts and nuts.
synthetic fibres such as glass. In the recent work by Also the unproductive friction and wear is equally
Shalwan and Yousif (2013), it is highly considerable such as gas turbine, cams and bearings,
recommended further studies on the thermoset and external combustion engines, (Bhushan et al.,
composites to identify the wear and frictional 1995). Nevertheless, the influences of deformation
characteristics of thermoset composites based on and adhesion of friction are addressed. Friction on
glass fibres. This motivates the current study. In the surface energy is affected by different factors which
current report, the wear and frictional behaviour of are sliding velocity, applied load, and temperature,
two fibre thermoset composites are considered as (Myshkin et al., 2005). In addition, the authors have
epoxy and polyester. Three different orientations of reported that friction comprises of three elements
fibre with respect to the sliding distance are namely, interfacial bonds, strength, and shearing and
accounted in the study and different sliding distance rupture of rubbing around the contact area of
0- 15 km. As a result of the rapid development that materials. It may also lead to damage materials’
the world witnesses and the challenge in using metal surface and then change the mechanical properties of
materials in tribological industrial applications, the the composite. Finally, the results from friction are
tribological behaviour of polymeric composites has temperature during converting mechanical energy to
recently experienced a create development, and heat, this heat is produced by friction and
attention by many researchers. Fibre reinforced deformation of materials leads to generate heat. On
polymeric composites have numerous advantages the other hand, few beneficial applications are
compared to the metal materials due to their provided by the friction such as tyres, and brakes
competitive mechanical properties of high specific friction. There are several studies have been done to
strength, low weight, low cost of raw materials, low inspect the tribological performance of polymeric
processing cost etc. Recently, composites materials composites based on synthetic fibres such as glass,
are heavily used in many applications that have been (Pihtili, 2009). Carbone fibres were investigated by
determined for these materials. Furthermore, (Suresha and Kumar, 2009). From the literature, there
67
is a lack of understanding on the tribological and different orientations of fibres were displayed in
behaviour of thermoset composites based on Fig.2.
synthetic fibres such as glass. In the recent work by
Shalwan and Yousif (2013), it is highly
recommended further studies on the thermoset Glass
composites to identify the wear and frictional
characteristics of thermoset composites based on
glass fibres. This motivates the current study.
In the current article, the wear and frictional
behaviour of two fibre thermoset composites are
considered as epoxy and polyester. Three different Epox
orientations of fibre with respect to the sliding y
distance are accounted in the study and different
sliding distance 0- 15 km.
68
lengths, widths, and weights. 20-30mm, 450g/m2 are 2.2.2 Experimental Procedure
used as measurements of current specimen of fibre The experiments were processed at appropriateness
lengths and mass of fibre respectively. (Revesol parameters hich are constant applied load ( )
P9509) is an unsaturated and addition of Methyl sliding velocity of . m s and sliding distance ( -
Ethyl Ketone Peroxide (MEKP) which can be used m) at room temperature ( C). he used of a ne
for ambient the surrounding temperature. Kong Tat specimen had to be done for each sliding distance.
Company of fiberglass engineering (Malaysia) has Before and after the test, the dry soft brush cleaned
been provided both reinforcement and polyester the prepared composite specimen continually. Serta
materials. weight balancer (±0.1mg) being used in this
operation to determine and ensure the weights of the
2.2. Experimental set up and procedure composite specimen before and after test and then
2.2.1 Experimental set ups weight loss was evaluated. In addition, thermo-
Block-On-Ring (BOR) is the main machine that it has imager camera was applied as so to determine the
been used to conduct the experiments. The specimens initial interface temperature. SEM (JEOL) was used
surface (10mm*10mm*20mm) was tested against a to investigate the composite surface morphology.
counterface made of stainless steel (AISI 304, The composite specimen surface was coated before to
hardness =1250HB, Ra=0.1µm). Before each test, use the SEM machine. Thus, each tribological test
(Sic G2000) was utilized to smooth the counterface was repeatedly done several times and the average of
and thereafter a piece of wet cloth with acetone was the magnitudes was measured. The weights of the
used to clean the counterface. Fig. 3 shows the block specimens before and after test using Sera balancer
on ring step up showing the load cell, samples, and then specific wear rate were determined for each
counterface and the sample holder. The load cell is test condition by using Eq1.
connected to the computer to capture the frictional
force during the experiments. (1)
69
3.1.1. Wear Behaviour Regarding to the composite, (AP-O) orientation
In order to study the wear behaviour of neat epoxy, indicates poorly wear rate compared to (P-O) and (N-
(NE), neat polyester (NP), glass fibre reinforced O) orientations, the composite in (P-O) and (N-O)
epoxy (GFRE) and glass fibre reinforced polyester directions exhibit lower wear rate after sliding
(GFRP), a series of experiments have been conducted distance of 5 km. moreover, in comparison with Neat
at different operating parameters and orientations. epoxy and three orientations found that AP-
The orientations are (N-O, P-O, and AP-O) orientation has approximately 30% less than Neat
The specific wear rate of the GFRE and NE against epoxy while P and N orientations gave about (20%
the sliding distance of different orientations is given less). The realization for this can be explained that
in Fig. 4.a. Since the specific wear rate (SWR) value the proportionally harder phase (CSM) is pulled out,
of all the selected materials is very small, the broken, fractured of glass fibres and removed from
presented values are multiplied by 1000000, and i.e. CSM. It is generally accepted that the weight loss of
the values should be multiplied by E-6. Moreover, the the composite specimens have significantly increased
specific wear rate of the epoxy is relatively high with the effect of constant sliding velocity and sliding
compared to its composites that are why its values are distance when applied load was about 30 N.
on the right vertical axis with different scale. From The results of specific wear rate of glass/polyester
this figure, one can see that the neat epoxy exhibits and neat polyester versus the sliding distance of
very high specific wear rate and reached the steady different orientations is represented in Fig 4.b. It
state after about 5 km. on the other hand, the epoxy shows the specific wear rate of glass/polyester at
composites show lower specific wear rate compared various orientations with the neat polyester. Since
to the neat epoxy for all the fibre orientations. The the highest wear rate value is registered for the (P-O)
steady state of the composites reached after about 10 at sliding distance of about 3 km since the interaction
km since the interaction between the asperities took between the hardness some time to adopt, the right
longer time to adopt. Further explanation will be vertical axis is presented the values of specific wear
given with the assist of the roughness profile in the rate. Because the specific wear rate (SWR) is very
next section. small, the obtained values are multiplied by 1000000.
It is generally seen that the polyester composites
0.07 0.25 show the highest specific wear rate for (AP-O and N-
0.06 O) at approximately 3 km. Likewise, the composites
0.2 reached the steady state after 6 km. Concerning to
0.05
the composite, the wear rate has significantly
SWR, mm3/N.m 10-6
0.04 0.15
GFRE-NO decreased with increasing the sliding distance for the
0.03 GFRE-AP 0.1 orientations, i.e. (AP-O and N-O) This lowering is
GFRE-P pronounced after about 3 km. After about 6 km all
0.02
0.05 the composites have reach the steady state.
0.01
Meanwhile, for (N-O) gives less wear rate compared
0 0 to the others for all levels of sliding distances are
0 5 10 15 20 tested. Furthermore, there is no markedly difference
Sliding distrance, km
in wear rate for all the composites when they reached
b) GFRE the steady state. Differently, in comparison with (N-
0.5 0.5
0.45 0.45 O) exhibits less wear rate at lower sliding direction
0.4 NEAT P 0.4 and slightly decrease in wear rate at higher sliding
0.35 GFRP N-O 0.35 distance. It is accepted that glass fibre gives superior
SWR, mm3/N.m 10 -6
GFRP-AP-O
0.3 GFRP P-O 0.3 wear performance and through the sliding of the (N-
0.25 0.25 O) orientation. (Ws) Values of the composites are
0.2 0.2 obviously decreased as a result the better wear
0.15 0.15 behaviour of the composite is achieved for (N-O).
0.1 0.1 Therefore, it can be due to the reinforcement of the
0.05 0.05 adhesion properties between the glass fibre and the
0 0
0 5 10 15 20
polyester resin. From the mechanical point of view,
Sliding distance,km the interface adhesion is enhanced the mechanical
characteristics of the composite. hus the material’s
c) GFRP strengthens is another reason, which can cause to
Fig. 4 Specific wear rate against sliding distance of lower weight removal. However, Summary of the
neat polyester, neat epoxy, GFRP and GFRE specific wear rate of the selected materials after
composites reaching the steady state at 10 km is shown in Fig.5.
It seems that there is universal value of specific wear
70
rate of GFRE and GFRP in which the best wear orientation exhibits the lowest value of (0.25-0.3)
performance can be achieved, i.e. (N-O) for both than the others.
fibre composites exhibited an optimum value. On the The effect of sliding distance and applied load on
other hand, neat epoxy and neat polyester are reached friction coefficient of GFRP is presented in Fig 6.b.
the highest value for both composite. GFRP is shown In addition to that, the influence of glass fibres on the
the higher value compared to GFRE in the case of tribological behaviour of the neat polyester and the
(AP-O). Moreover, there is markedly difference value composite are clarified.
between the composites in (P-O). However, the Regarding to the composite, the findings of friction
optimum wear value is produced in the (N-O) for coefficient are provided as a function of sliding
both materials. Due to the lowering in the hardness of distance at 30N applied load. Generally, it can be
the film in the composite surface this can be related seen that the friction coefficient increases at the
to the mechanical properties in term of interfacial beginning and starts to reduce at approximately (5
adhesion and strength. km) sliding distance. However, it appears that
normal and anti-parallel (N-O and AP-O) orientations
0.07 0.06 have achieved the lowest friction coefficient at the
GFRP applied load of 30N which are about 0.23 and 0.28
0.06 0.05
GFRE respectively. Consequently, the higher value of
0.05 friction coefficient is evident for the neat polyester,
Ws,mm³/N.m 10 -6
0.04
which is about 0.42 while the glass fibre composite at
0.04
0.03 different orientations exhibit 0.2 to 0.3 of friction
0.03 coefficient. There is no significant effect on the
0.02 friction coefficient at different sliding distance. It
0.02
can be seen that friction coefficient does not reach
0.01 0.01 steady state at all sliding distance. Nevertheless, the
friction coefficient is minimized whilst the sliding
0 0
NEAT N-O P-O AP-O distance increasing.
Materials' Orientations
71
This cause can be due to the strongly transfer film on indicated that temperature trend is elevated gradually
the counterface and the existence of the fibres and when the sliding distance has long term effect on the
polyester. During longer sliding may lead to impairs composite. However, these outcomes have been
the adhesion between the two sliding surfaces and gained with the assist of thermo-imager camera
then associated interaction takes place between them. which has been used for every separate experiment at
The influence of the friction coefficient and wear 30 N applied load, 2.8 m/s sliding velocity.
performance will be illustrated by the help of the Meanwhile, the GFRE (N-orientation) is examined at
micrographs of the composite's worn surface. With 2.8 m/s, increasing in the sliding distance does not
regards to the glass fibre polymer composite, the observe any change in the temperature from 10 km
friction coefficient of both GFRP and GFRE are until 14km.
summarised in Fig 7. The highest friction coefficient Fig 8.b shows the maximum interface temperature
during tribological conditions at 10 km is represented that is evaluated during the rubbing, i.e. at sliding
for neat composite. However, the friction coefficient distance 15km at 30N. The highest interface
is high for other direction of the composite. This can temperature is measured due to the high friction
be noted that the deponding of fibre and the strong of coefficient of NP and GFRP (in P-O); higher
interfacial adhesion are avoided breakage and interface temperature is gauged in NP compared to
bending. As a result, (AP-O) show the lowest friction NE composite. Since AP-O has the lower
value for both materials. Whereas, (N-O) in GFRE temperature value than GFRE (in AP-O). Generally,
has a higher value than (N-O) in GFRP. However, the sliding distance has close relation with the
(AP-O) in GFRP is achieved the lowest value interface temperature, and friction coefficient of the
compared with all the orientations for both entire composite are increased. Therefore, we can
composite. record that the temperature starts in increase after 10
km. Finally, thermo-image camera has been applied
0.6 0.6 for every test and provided more results.
GFRP GFRE
0.5 0.5
Friction Coefficient,µ
0.4 0.4 60
GFRE,N 30N
0.3 0.3 50 GFRE,APO 30N
0.2 0.2 GFRE, PO 30N
Temperature C
40 NE,30N
0.1 0.1
30
0 0
NEAT N-O P-O AP-O
20
Materials's Orientations
Fig. 7 Summary of the friction coefficient of the 10
selected materials after reaching the steady state after
10 km sliding distance 0
0 2 4 6 8 10 12 14 16
3.1.3. Interface Temperature Sliding distance,km
Fig 8.a shows the influence of the applied load and a) GFRE
different sliding distance on the interface temperature 60
of GFRE composite in different orientations (N-O, P- GFRP,N-O
GFRP,AP-O
O, and AP-O) and the comparison with the neat 50 GFRP,P-O
epoxy composite. The friction coefficient, applied NP
load and sliding distance are maximised. As a result, 40
Temperature
72
3.1.4. Composite surface observation 3.536m. However, the roughness profile of the AP-O
Further explanation will be exhibited with the assist is the lower value. Fig.10.b shows the relation
of the roughness profile in the next dictation. The between the roughness values of the GFRP after test
results from the test are recorded in the direction of under 30N applied load for 15 sliding distance. In
the counterface and against the direction of the addition to that, the roughness profile of the neat
counterface. Fig.9 shows some samples of the polyester is slightly decrease compared to the surface
roughness profile of the selected materials roughness profile of the neat epoxy in the previous
GFRE/GFRP at different operating parameters. On section.
the other hand, Fig.10 summarises the roughness Fig.11 shows the effect of the sliding distance on the
values of the selected materials after test under 30 N worn surface of the GFRE and GFRP composites.
applied load for 15 km sliding distance.Fig.10.a Concerning the composite, severe damage on the
presence the roughness value of GFRE. It seems that worn surface of the GFRE (N-O) is recorded. At the
the highest value is recorded in the case of (AP-O) in maximum value of the sliding distance the rubbing is
the direction of the counterface while the lowest partially different compared with lower distance. In
value is provided in (P-O). Compared to the GFRE, order to reduce the friction coefficient, a set of fibre
Fig.10.b shows significantly reduce the roughness has been removed and peeled off from the rubbing
value of the GFRP in (AP-O) for both directions; area. At 2Km and 30 N, there is no indication of
moreover, one can notice that (P-O) shows less effect movement of fibres. Whereas, micro-cracks have
value on the counterface in the direction of the risen on the surface, indicate the elevated wear
counterface. performance of the composite at the rubbing region.
As a result, it can be concluded that at ruthless
conditions of higher load and/or sliding distance
micro-cracks dominate on the wear resistance of
GFRE in (N-O).
a) GFRE
73
The weakened interfacial adhesion in the fibre end is
between the fibre and the resin zone. This concludes
that (at sliding distance) the wear mechanism of
GFRP in N-O is dominated which related with the
same orientation and its wear mechanism
4. Discussion And Comparison With Previous
Fibre Micro-crack Published Works
Debondi In this chapter, the experimental results on neat
epoxy, glass fibre reinforced epoxy/polyester
composite in three orientations as (N-O, P-O, and
AP-O) are compared with some of the studies in
terms of weight loss and frictional behaviour at
various operating parameters. Fig 13 presents several
researches and studies that have determined the
values of specific wear rate and frictional behaviour
Debris of several composites, and current outputs are painted
of different colour. Shi et al., (2003) have
investigated the highest value of specific wear rate of
neat epoxy composite compared to the specific wear
rate of this work (Shi et al., 2003). Furthermore, neat
polyester has marked the lower friction coefficient
and weight loss, specific wear rate and friction
coefficient were measured about (0.03234), and
(0.23) respectively, (El-Tayeb, 2008). Moreover, the
Fig. 11 Micrographs of GFRE worn surface after the present specific wear rate of glass fibre/epoxy shows
test under 30 N applied load in N-Orientation the lowest value and the highest friction coefficient is
recorded than the other one which was studied by
Fig.12 represented that micrograph of GFRP worn Pihtili (2009)(Pihtili, 2009). The friction coefficient
surface after the test under 30 N applied load in AP- and wear rate of glass fibre/polyester composite are
Orientation.. shown in figure below. The same friction coefficient
is produced compared to the value was defined by
Shalwan and Yousif (2012) (Yousif, 2012).
Fibre end However, glass fibre/polyester exhibits low specific
wear rate (0.02).
Plastic
74
5. Conclusions 6. Unal, H., et al., Sliding friction and wear
Few points are concluded as follows: behaviour of polytetrafluoroethylene and its
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glass fibre reinforced epoxy composite, the better and polymer-based composites. Journal of
wear and frictional behaviour were performed when Materials Education, 2010. 32(5): p. 273.
the composite was tested in N-O. 8. Bhushan, B., J.N. Israelachvili, and U.
2. The fibre orientations has highly influence Landman, Nanotribology: friction, wear and
and similar in controlling the friction and wear lubrication at the atomic scale. Nature, 1995.
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composite is consistently and essentially high in AP- 9. Myshkin, N.K., M.I. Petrokovets, and A.V.
O compared to N-O of the composites. Moreover, Kovalev, Tribology of polymers: Adhesion, friction,
the sliding distance and applied load have a little wear, and mass-transfer. Tribology International,
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3. The detachment and breakage of fibres were 10. Suresha, B. and K.N.S. Kumar,
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different wear mechanisms. For the GFRP, plastic
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12. Shi, G., et al., Friction and wear of low
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nanometer Si3N4 filled epoxy composites. Wear,
5. Even though, the increasing temperature and
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effect on the tribological properties of both polymeric 13. El-Tayeb, N.S.M., A study on the potential
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75
APPENDIX C: FURTHER RESULTS
1) Scanning electron microscopy observation
For GFRE
Glass Fibre
Epoxy
76
For GFRP
Fibre End
Plastic Deformation
77