ROLE OF FIBER-MATRIX INTERFACE ON MECHANICAL AND
TRIBOLOGICAL PROPERTIES OF CARBON FABRICPOLYETHERIMIDE COMPOSITES
by
SUDHIR TI WAR!
Industrial Tribology Machine Dynamics and Maintenance Engineering Centre
(ITMMEC)
Submitted
in fulfillment of the requirements of the degree of
Doctor of Philosophy
to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI
FEBURARY 2011
CERTIFICATE
This is to certify that the thesis entitled "Role of Fiber-Matrix Interface on Mechanical and
Tribological Properties of Carbon Fabric-Polyetlrerimide Composites" being submitted by
Mr. Sudhir Tiwari to Industrial Tribology Machine Dynamics and Maintenance Engineering
Centre (ITMMEC), Indian Institute of Technology Delhi is worth of consideration for the award
of degree of Doctor of Philosophy and is a record of the original bonafide research work carried
out by him under our guidance and supervision and has fulfilled the requirement for the
submission of this thesis, which to our knowledge has reached the requisite standard.
The results contained in this thesis are original and have not been submitted, in part or full, to
any other University or Institute for the award of any degree or diploma.
Dr. Stephane Panier
Associate Professor
Polymers and Composites Technology
& Mechanical Engineering Department
Ecole des Mines de Douai, Douai Cedex
France
Dr. Jayashree Bijwe
Professor
Industrial Tribology Machine Dynamics
and Maintenance Engineering Centre (ITMMEC)
Indian Institute of Technology Delhi
Acknowledgement
First of all I would like to offer utmost thanks to Lord Shiva for his benevolent shower of
grace that led me throughout this arduous work, which would have been otherwise impossible.
I find words falling short in expressing the multitude of ever flowing gratitude to my
supervisors Prof. Jayashree Bijwe and Dr. Stephane Panier, because of their impetus,
sustained efforts, able and persistent guidance, the research work could be undertaken and
fostered me with the strength and spirit to see to its culmination.
I would like to extend my sincere thanks to Prof. N. Tandon, Head ITMMEC and the
members of my Ph. D committee Dr. Mangla Joshi and Dr. R. K. Pandey.
I take immense pleasure in expressing my sincere gratitude to Prof. P. R. Bijwe, whose
affection and blessings kept me going throughout this period.
My sincere thanks to Prof. Brigitte Mute!, University of Lille, France for extending the
facility of plasma treatment to the carbon fabric.
I extend whole hearted thanks to Dr. P. S. Datta, Principal Scientist, Division of
Agriculture Physics, IARI, New Delhi, India for extending y-irradiation facility for this work.
My special thanks to colleagues, Dr. Nidh Dureja, Dr. Bimlesh Lochab, Dr. Mukesh
Kumar, Mr. Mohit Sharma, Ms. Sini N.K., Mr. N. Aranganathan, Mr. Ajay Kadiyala, Mr.
Sanjeev Sharma and Mr. Kuldeep Singh for their all time cooperation and help during the
entire period.
I would like to thank to all the technical staff of ITMMEC for their cordial association
and help rendered during the tenure of this work especially Mr. Avtar Singh (JTS), Mr. Pratap
Chand (JLA), Mr. Samaivir Singh (SLA), Mr. Mohan Singh (JTS), Mr. S. K. Kapoor (JTS) and
Mr. J. Tuteja (Lab Suptd.).
It is my pleasure to express my indebtedness to my Parents for their love and moral
support which has kept me intact and spirited throughout this work.
I express my deep heartfelt gratitude to my beloved wife Bhawana for her patience,
understanding, incessant love and co-operation throughout this period.
(Sudhir Tiwari)
ii
ABSTRACT
Studies on the tribology of fiber reinforced polymer matrix composites have assumed a
paramount significance in the current scenario which demands high performance and thermally
stable tribo-materials which can perform reliably under high PV conditions without applying any
conventional lubricants. Contemporary research being dominated by development of newer
materials with multiple applications, it was aimed to develop composites based on carbon fabric
(CF) and thermoplastic specialty polymer, Polyetherimide (PEI). These in the form of
composites materials have immense potential for structural components as well as triboapplications such as bearings, gears, bearing cages, bushes, slides wherein the components
encounter severe damages due to combination of wear modes operative simultaneously such as
adhesive, abrasive, fretting, fretting-fatigue etc. The fabric reinforcement is unique in the sense
that it provides bidirectional strength and possesses a drape quality that facilitates ease in
production of complex shaped parts without wrinkles. Carbon fibers are widely used as
reinforced materials in composite due to their interesting properties such as high specific
strength, high thermal resistance, low expansion coefficient etc. Carbon fibers, though very
expensive, are most favored for tailoring high performance composites and tribo-composites.
Their surface, however, is chemically inactive/inert leading to the most potential problem of
inadequate adhesion and hence weaker composite. It is desired to treat them with a proper
treatment prior to its use in composites. Several types of reported surface treatments of carbon
fibers are classified in two categories. First, improves adhesion by enhancing physical bonds
such as by roughening it leading to more surface area and a large number of contact points,
micro-pores or surface pits on already porous carbon fiber surface. The second on other hand,
iii
involves chemical reactions leading to inclusion of reactive functional groups that promote good
chemical bonding with the polymer matrix.
Interestingly any surface treatment method especially, which etches fiber's surface also leads to
affect the strength of fiber adversely. First effect called as positive effect leads to enhancement in
fiber-matrix adhesion and hence improvement in strength of composite since matrix supports the
fibers more firmly. Simultaneously, other effect which is in negative direction reduces the
strength of fibers due to etching contributing to deteriorate the strength of composite. The final
strength composite depends on net contribution of these two opposing effects. It is hence
imperative to optimize the extent of treatment to get the maximum possible enhancement in
performance properties of composite. Since adequate literature is not available, it was decided to
treat the CF by HNO3, cold remote nitrogen-oxygen plasma (CRNOP), gamma (y) ray irradiation
and rare earth compound (YbF3) with varying doses and to develop 4 series of composites with
Polyetherimide (PEI) keeping all other parameters such as type and amount of CF (PAN based,
twill weave, z 55-56%vol), processing technique (impregnation followed by compression
molding) constant so that the performance of all the composites could be compared. The
selection of treatment methods was done in such a way that either no papers on treatment are
available (e.g for Nano-particles) or no papers are available on their exploration for tribological
applications (e.g. y- radiation and CRNOP) or a method though very popular but not investigated
systematically (e.g. HNO3).
Based on this in all, 4 series of composites (total 17 composites) were developed, characterized
and tribo-evaluated in adhesive and abrasive wear modes.
Chapter 1 elaborates on the introduction to the subject followed by gaps in literature and
motivation to work with objective and research plan.
iv
Chapter 2 presents detailed literature survey on various treatment methods for CF and their
influence on various properties of fibers and the composites developed based on these treated
fibers including tribo-performance.
Chapter 3 elaborates on the details of materials procured and methods selected for surface
treatment of CF followed by formulation, development of 4 series containing 17 composites
based on treated fabric along with their designations.
Chapter 4 presents characterization techniques {Scanning Electron Microscopy (SEM), Fourier
Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR), Raman
spectroscopy and mechanical testing) used for fibers (untreated and treated) along with the
results. It also presents the details of characterization techniques for composites for physical
(density and % of fibers and voids) and mechanical properties {tensile strength (TS) and tensile
modulus (TM), flexural strength (FS) and flexural modulus (FM), and interlaminar shear strength
(ILSS)} were evaluated following the ASTM standards. All treatment methods showed
significant improvement in mechanical properties of the composites. In each series the best
performers were;, 1% 02+N2 plasma; 90 minutes of HNO3 oxidation; 300 kGy of y- rays dose
and 0.3 wt% of YbF3. The improvement in ILSS of composites due to plasma, HNO3, y and YbF3
treatment was 53%, 71%, 58% and 61% respectively. Overall it was observed that
•
Treatment increased roughness of the fiber surface, which increased the surface area and
provided more cites for better mechanical interlocking between the fiber and matrix.
•
FTIR-ATR analysis confirmed presence on oxygenated functional groups on CF after
treatment, which increased chemical reactivity of the fiber.
•
Significant reduction in TS of fibers was observed for HNO3, while for plasma, y and
YbF3 treatment reduction was marginal.
v
a
Optimum value of dose of treatment was observed for HNO3 and YbF3 cases while for
others properties increased continuously.
Chapters 5 presents on the studies on adhesive wear of composites including methodology and
selected operating variables followed by results, discussions, worn surface analysis and
conclusions. Treated fabric composites showed superior properties and trends followed the
pattern in the mechanical properties in general.
Chapter 6 focuses on the abrasive wear of composites including methodology, results, and
discussion and SEM studies on the worn surfaces. Treated fabric composites showed superior
properties and wear trends followed the pattern in the mechanical properties especially ILSS.
Chapter 7 presents salient conclusions on the studies carried out on the 17 composites, followed
by the scope for future work.
The treatment of fiber proved beneficial in improvement of mechanical performance of
composites. Adhesive wear properties of composites were significantly improved after treatment
of fabric. The nano-sized YbF3 treatment proved most effective while plasma treatment was
least effective. In case of abrasive wear the HNO3 treatment proved most effective while plasma
treatment provided the least improvement in the performance.
vi
CONTENTS
Acknowledgement
i
Abstract
iii
List of Figures
xiv
List of Tables
xix
List of Abbreviations
xx
Page No.
1. INTRODUCTION
1.1 Polymer Materials and Composites as Tribo-materials
1.1.1 Types of fiber reinforced composites
1-22
1
3
1.1.1.1 Short fiber reinforced composites
3
1.1.1.2 Unidirectional (UD) fiber reinforced composites
3
1.1.1.3 Bi-directional fiber reinforced composites
4
1.2 Factors Influencing the Performance of BD Composites
4
1.2.1 Type of matrix
4
1.2.2 Type of reinforcement
5
1.2.3 Amount of fabric
5
1.2.4 Orientation of fabric with respect to the loading direction
5
1.2.5 Types of weave
6
1.2.6 Processing techniques
6
1.2.7 Quality of fiber-matrix interface
7
1.3 Carbon Fiber as a Reinforcement- Limitations and Remedies
7
1.4 Surface Treatment of the Carbon Fibers
7
1.5 Surface treatment of Fibers-Positive and Negative Effects
8
1.6 Treatment of Carbon Fibers-State of Art
9
1.6.1 Oxidation treatment
9
1.6.2 Plasma treatment
10
1.6.3 Gamma radiation treatment
10
vii
1.6.4Rare-earth salt suspension treatment
10
1.6.5Combination of methods
10
1.7 Research Gaps and Motivation of the Proposed Work
11
1.8 Objectives
13
1.9 Research Plan
13
2. Literature Survey
2.ATreatment of Carbon Fibers and its Effect on Fiber Properties
23-52
23
2.A.1Oxidation treatment
24
2.A.2 Plasma treatment
26
2.A.3Gamma ray radiation treatment
28
2.A.4 Rare earth compound treatment
29
2.A.5 Combined treatment methods
32
2.BEffect of Fiber Treatment on Performance Properties of Composites
2.B.1Oxidation treated fiber composites
33
33
2.B.1.1 Mechanical properties
33
2.B.1.2 Tribological properties
34
2.B.2Plasma treated fiber composites
36
2.B.2.1 Mechanical properties
36
2.B.2.2 Tribological properties
37
2.B.3Gamma radiation treated fiber composites
37
2.B.3.1 Mechanical properties
37
2.B.3.2 Tribological properties
39
2.B.4Rare earth compound treated fiber composites
2.B.4.1 Mechanical properties
39
40
VIII
2.B.4.2 Tribological properties
41
2.B.5 Miscellaneous methods for CF treatment
43
2.B.6 Combined treatment studies
44
2.B.6.1 Mechanical properties
44
2.B.6.2 Tribological properties
46
3.Material and Methodology
3.1 Selection of Materials
53-63
53
3.1.1Selection of reinforcement for the composites
53
3.1.2Selection of the Polymer Matrix
54
3.1.3Selection of the nano-powder for the treatment
56
3.2 Selection of Treatment to Carbon Fabric
56
3.2.1Oxidation treatment
56
3.2.2 Plasma treatment
56
3.2.3Gamma irradiation treatment
59
3.2.4 YbF3 treatment
59
3.3 Development of Composites and Designations
Appendix A
4.Characterization of Carbon Fibers and Composites
4.1 Characterization of Materials
4.1.1 Studies on surface of a carbon fabric
61
63
64-109
64
64
4.1.1.1 Scanning electron microscopy (SEM) and Field emission64
scanning electron microscopy (FESEM)
4.1.1.2 Fourier transforms infrared spectroscopy-Attenuated total65
reflectance (FTIR-ATR)
4.1.1.3 Raman spectroscopy
65
4.1.1.4 Fiber tow tension test
65
ix
4.1.1.5 Fiber-matrix adhesion test
4.1.2 Studies on composites
4.1.2.1 Physical characterization
•
•
•
;ON
:.
:.
Density of composites
Fiber weight and volume fraction
Void content (vol. %)
4.1.2.2 Mechanical characterization
•
•
•
Tensile strength and modulus
Flexural strength and modulus
Interlaminar shear strength (ILSS)
4.2 Results and Discussion
4.2.1 Studies on fibers
4.2.1.1 HNO3 treated CF
•
•
•
•
•
•
SEM analysis
FESEM analysis
FTIR-ATR analysis
Raman Spectroscopy analysis
Fiber tension test
Fiber matrix adhesion analysis
4.2.1.2 Plasma treated CF
•
•
•
•
•
•
76
SEM analysis
FESEM analysis
FTIR-ATR analysis
Raman Spectroscopic analysis
Fiber tension test
Fiber matrix adhesion analysis
4.2.1.3 Gamma ray treated CF
•
•
•
69
81
SEM analysis
FESEM analysis
FTIR-ATR analysis
x
•
•
•
Raman Spectroscopic analysis
Fiber tension test
Fiber matrix adhesion analysis
4.2.1.4 YbF3 treated CF
• SEM analysis
• FESEM analysis
• FTIR-ATR analysis
• Raman Spectroscopic analysis
• Fiber tension test
• Fiber matrix analysis
4.2.2 Studies on composites
86
92
4.2.2.1 HNO3 treated CF composites
•
•
Physical properties
Mechanical properties
4.2.2.2 Plasma treated CF composites
•
•
Physical properties
Mechanical properties
4.2.2.3 Gamma ray treated CF composites
•
•
Physical properties
Mechanical properties
4.2.2.4 YbF3 treated CF composites
•
•
7l7
Physical properties
Mechanical properties
4.3 Comparative performance evaluation
4.4 Conclusions
•
•
•
•
101
HNO3 treated samples
Plasma treated samples
Gamma ray treated samples
YbF3 treated samples
xi
5.Adhesive Wear Studies of Composites
5.1 Methodology of Evaluation of Adhesive Wear Performance
110-147
110
5.1.1Experimental set-up
110
5.1.2Operating parameters
112
5.2 Results and Discussion
112
5.2.1HNO3 treated CF composites
112
5.2.2 Plasma treated CF composites
120
5.2.3 Gamma ray treated CF composites
130
5.2.4 Ytterbium fluoride (YbF3) treated CF composites
138
5.2.5 Comparative Performance Evaluation
145
5.3 Conclusions
6. Abrasive Wear Studies of Composites
6.1 Methodology of Evaluation of Abrasive Wear Performance
146
148-185
148
6.1.1Experimental set-up
148
6.1.2Operating parameters
151
6.2 Results and Discussion
151
6.2.1HNO3 treated CF composites
151
6.2.2 Plasma treated CF composites
161
6.2.3 Gamma ray treated CF composites
170
6.2.4 Ytterbium fluoride (YbF3) treated CF composites
175
6.3 Comparative performance evaluation
7. Conclusions and Scope for Future Work
181
186-198
7.1 Overview of the work
186
7.2 Major Conclusions
187
xii
7.2.1 Effect of treatment on CF properties and mechanical performance of 187
composites
(a) Tensile property
(b) Flexural property
(c) ILSS
7.2.2 Effect of treatment on tribological performance of Composites190
(a) Adhesive wear mode
(b) Abrasive wear mode
7.3 Scope for Future Work
Appendix-A
198