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Ul-JIVf !\c : i l 1 TI-'KNPI OGi MALAYSIA
PSZ 19:16 (Pind. 1/97) UNIVERSITITEKNOLOGI MALAYSIA
BORANG PENGESAHAN STATUS TESIS<
JUDUL: THE EFFECT OF BUCKLING IN FRP MEMBERS
SESIPENGAJIAN: 2005/2006
Saya MOHD HALIMIRWAN BIN IBRAHIM
(HURUF BESAR)
mengaku membenarkan tesis (•PSM/Sarjana/Doktor Falsafah)* ini disimpan di Perpustakaan Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hakmilik Universiti Teknologi Malaysia. 2. Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan
pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara
institusi pengajian tinggi. 4. * * Sila tandakan (V)
• SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)
• TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
m TIDAK TERHAD
(TANDATKNGAN PENULIS)
Disahkan ol
(TANDATAICGAN PENYELIA)
Alamat tetap: NO. 57-1, BATU 2
KG. PADANG TEMU,
75050 MELAKA
DR YOB SAED ISMAIL
Nama Penyelia
Tarikh: NOVEMBER 2005 Tarikh: NOVEMBER 2005
CATATAN: * Potong yang tidak berkenaan. ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak
berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.
• Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Saijana secara penyelidikan, atau disertasi bagi pengajian secara keija kursus dan penyelidikan, atau Laporan Projek Saijana Muda (PSM).
School of Graduate Studies
Universiti Teknologi Malaysia
UTM(PS)-l/02
VALIDATION OF E-THESIS PREPARATION
Title of the thesis : THE EFFECT OF BUCKLING IN FRP MEMBERS
Degree: MASTER OF ENGINEERING (MECHANICAL - PURE)
Faculty: FACULTY OF MECHANICAL ENGINEERING
Year: 2005/2006
I MOHD HALIM IRWAN BIN IBRAHIM
(CAPITAL LETTER)
declare and verify that the copy of e-thesis submitted is in accordance to the Electronic Thesis and
Permanent address:
NO. 57-1, BT. 2 V*, Name of Supervisor: DR. YOB SAED ISMAIL
KG. PADANG TEMU, Faculty: MECHANICAL ENGINEERING
75050 MELAKA
Note: This form must be submitted to SPS together with the CD,
'^fAVe* hereby declare t h a t h a v e read this thesis and in vfxf/om* opinion
this thesis is sufficient in terms of scope and quality for the award of the
degree of Master of Engineering (Mechanical-Pure)"
Signature
Name of Supervisor
Date
Signature
Name of Co-supervisor
Date
Wit. t ...^./../rtrl.-*^.^......
_ i . S / . f ^ f o . C ^ i "
* Delete as necessary
THE EFFECT OF BUCKLING IN FRP MEMBERS
MOHD HALIM IRWAN BIN IBRAHIM
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Mechanical - Pure)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
NOVEMBER 2005
ii
I declare that this thesis entitled " The effect of buckling
in FRP members " is the result of my own research except
as cited in the references. The thesis has not been accepted for any degree
and is not concurrently submitted in candidature of any other degree.
Signature
Name
Date
Mohd Halim Irwan Bin Ibrahim
1 / I X / 0 5
iii
To my 6e(ovecffamiCy ;fatfier motfier, my Brothers; ftisHam, fiafezi andfianiff.
Tfianf^ufor allyour supports, commitments and guidance. Last But not least to my Beloved
one ;Norfiazrin; u're my inspiration andthankjifor everything.
ACKNOWLEDGEMENT
I would like to express my sincere gratitude to my main project supervisor, Dr.
Yob Saed Bin Ismail, for encouragement, guidance and friendship. I am also very
thankful to my co-supervisor, Mr. Shukur Abu Hassan for his guidance, advices, critics
and motivation. Without their continued support and interest, this project report would
not have been the same as presented here.
My sincere thanks also goes out to the technicians:-
• Mr. Rizal (Strength)
• Mr. Abd Hamid, Mr. Ayob & Mr. Basir (Store)
• Mr. Hasni (Metrology)
• Mr. Roslan, Mr. Azizi & Mr. Mohamad Ali (Manufacturing)
• Mr. Azri & Mr. Jefri (Material)
• Mr. Shamsudin (Composite)
• Mr. Raduan ( Foundry)
Besides that, I wish to express my appreciation to anyone who have contributed
a variety of ways towards the success of this project. Their views and tips are useful
indeed. Unfortunately, it's very difficult to list all of them in this limited space. Thank
you so much
Mohd Halim Irwan Bin Ibrahim
November 2005
XV
ABSTRACT
The field of composite materials is both old and new. It is only since the early
1960s have engineers and scientists exploited seriously the vast potential of fabricated
fibrous composite materials. Development of new composites and new applications of
composites is now accelerating. This project is a study of how the critical load changed if
we varying the length of strut. Besides that, we need to design the test rig that hold
column during the buckling test with using fixed-fixed as the boundary condition.
Comparison between the buckling test method and theoretical from resin burn-off test
data will be analysed and determine the suitable length that valid through compression or
buckling. Any error occurs between theoretical and experimental will be minimize by
modify the original equation of Euler Equation. Here, the aspects that we will see is the
factor which contribute to the effect of buckling whether the length, geometry, Young's
modulus or the volume fraction of fibres ,etc.
vi
ABSTRAK
Bidang komposit terdiri daripada unsur baru dan lama. Pada awal tahun 1960,
baru ada di kalangan jurutera dan saintis menceburkan diri secara serius dalam
penyediaan bahan komposit bergentian. Penyelidikan dalam bahan komposit dan aplikasi
yang terbaru berkaitan komposit semakin membangun. Projek ini adalah untuk mengkaji
bagaimana beban kritikal berubah jika diubah panjang topang. Selain itu, keperluan
merekabentuk peralatan ujian yang memegang topang semasa ujian ledingan dengan
keadaan sempadan terbina dalam di kedua sisi. Perbandingan di antara kaedah ujian
ledingan dan teori daripada data ujian pembakaran resin akan dianalisa dan seterusnya
penentuan panjang topang yang bersesuaian samada lebih terarah kepada pemampatan
atau ledingan. Sebarang ralat diantara teori dan eksperimen akan dikurangkan melalui
pengubahsuaian teori Euler. Di sini, aspek yang ingin kita amati ialah faktor yang
memberi sumbangan kepada kesan ledingan samada panjang topang, geometri, Modulus
Young atau isipadu kandungan gentian dsbnya.
vii
TABLE OF CONTENTS
DECLARATION
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF FLOW CHART
LIST OF FIGURES
LIST OF TABLES
LIST OF GRAPHS
CHAPTER TITLE PAGE
1 INTRODUCTION
1.1 Background 1
1.2 Problem statement 3
1.3 Objective 3
1.4 Scope of research 4
2 LITERATURE REVIEW
2.1 Introduction of fibres
2.2 Glass fibres
5
5
viii
2.3 Various forms of glass fibre 8
2.3.1 Roving 8
2.3.2 Chopped strands 9
2.3.3 Woven roving 10
2.3.4 Woven cloth 10
2.3.5 Chopped strand mat(CSM) 11
2.3.6 Surface tissue 12
2.4 Properties of glass fibre. 12
2.4.1 Mechanical strength 12
2.4.2 Environmental and corrosion resistance 13
2.4.3 Heat and fire resistance 13
2.4.4 Thermal conductivity 14
2.4.5 Thermal expansion 14
2.4.6 Electric properties 15
2.4.7 Density 15
2.4.8 Other characteristics 16
2.5 Pultrusion method (closed mould system) 17
2.6 Introduction of strut/slender column 21
2.7 Boundary conditions 23
2.7.1 Case 1: Both ends hinged 23
2.7.2 Case 2 : Both ends fixed 25
2.7.3 Case 3 : One endfixed and one end free 27
2.8 Buckling stress of strut 29
2.9 Validity level of Euler theorem 30
3 METHODOLOGY 33
4 EXPERIMENTAL SET-UP
4.1 Introduction 42
ix
4.2 Material's details 42
4.3 Test-rig preparation 45
4.3.1 CNC EDM Wirecut 46
4.4 Resin burn-off test 47
4.5 Buckling test 50
5 RESULTS AND DISCUSSION
5.1 Introduction. 53
5.2 Buckling test (experimental). 54
a) I-Bar 54
b) T-Bar 57
5.3 Burn-off test (experimental). 60
5.4 Theoretical calculation 63
a) I-Bar 63
b) T-Bar 67
5.5 How to determine the error? 73
5.6 Validity level 77
a) I-Bar 77
b) T-Bar 80
6 CONCLUSION AND RECOMMENDATION
6.1 Conclusion 83
6.2 Recommendation 86
REFERENCES 91
xi
LIST OF FLOW CHARTS
2.1 Flow diagram for the manufacture of glass fibre 8
3.1 Research methodology flow chart 41
M l
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Schematic diagram of the remelt method of
producing fiberglass 6
2.2 Roving 9
2.3 Chopped strands 9
2.4 Woven roving 10
2.5 Woven cloth 1 1
2.6 Chopped strand mat 11
2.7 Surface tissue 12
2.8 Effect of water and surfacc active agents on the
strength of glass fibres.(D.W Clegg) 17
2.9 Diagrammatic representation of pultrusion process 18
2.10 Euler Column 22
2.11 Behavior of Euler column/ideal strut 23
2.12 Both ends hinged 24
2.13 Both ends fixed 25
2.14 One end fixed and one end free 27
2.15 Graph acri, vs (L/k) - Euler Curve/Hyperbolic 30
2.16 Validity level for Euler Theorem 32
3.1 I-bar 33
3.2 T-bar 34
3.3 Boundary conditions of strut 35
3.4 Instron Machine with floor mounted load frame 36
xiii
3.5 Instron Machine with microprocessor-based control console 36
3.6 Test rig - (a), (b), (c), (d) 38
3.7 Heating element in furnace 39
4.1 I-bar specimen for experimental 43
4.2 T-bar specimen for experimental 43
4.3 2-D combination plotting of I-beam and T-beam 44
4.4 Test rig under buckling load 45
4.5 X-Y coordinate during cutting process of rig using CNC
EDM Wirecut 46
4.6 CNC EDM Wirecut 46
4.7 Furnace for resin burn-off test 48
4.8 Fibre system for I-bar after burn-off test 49
4.9 Fibre system for T-bar after burn-off test 50
4.10 Tightening the test-rig 51
4.11 Clamping the test-rig 52
4.12 I-bar specimen 52
5.1 Failure at the junction of T-bar 53
5.2 Neutral axis of I-bar 72
5.3 Neutral axis of T-bar 72
6.1 I-Bar - Used in this project 87
6.2 T-Bar - Used in this project 87
6.3 T-Bar - Use for next project 88
6.4 Recommended geometry for future study 88
6.5 Application areas of GFRP products 89
6.6 Pultruded fibreglass structural shapes 90
6.7 Practical application of GFRP bar 90
xiv
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Composition of various glass fibre grades. {Institute
of Structures and Design, Stuttgart, Germany) 7
2.2 Strength of various glass fibres at different stages
of processing. (Institute of Structures and Design,
Stuttgart, Germany) 13
2.3 Coefficients of thermal conductivity of various materials
compared to E-g\ass.(Institute of Structures and Design,
Stuttgart, Germany) 14
2.4 Coefficient of thermal expansion of E-glass and several
other materials. (Institute of Structures and Design,
Stuttgart, Germany) 14/15
2.5 Dielectric strengths of E-glass and various ceramics.
(Institute of Structures and Design, Stuttgart, Germany) 15
2.6 Densities of various fibres and d\\oys.(Institute of
Structures and Design, Stuttgart, Germany) 16
2.7 Sample physical properties of DURAGATE™ pultruded
components (conducted by SIRIM) 21
3.1 Instron Machine technical specification 37
4.1 Physical properties of specimen ( * MMFG Composites
Sdn. Bhd., Subang Jaya, Malaysia) 44
5.1 Experimental data for I-bar (0.4m) 54
5.2 Experimental data for I-bar (0.6m) 55
XV
5.3 Experimental data for I-bar (0.77m) 56
5.4 Experimental data for T-bar (0.4m) 57
5.5 Experimental data for T-bar (0.6m) 58
5.6 Experimental data for T-bar (0.77m) 59
5.7 Relation between En, E22 (* MMFG Composites Sdn. Bhd.) 60
5.8 Analysis burn-off data for I-bar 61
5.9 Analysis burn-off data for T-bar 61
5.10 Data for theoretical and experimental of I-bar 65
5.11 Data for theoretical and experimental of T-bar 69
5.12 Error between experimental and theoretical 73
5.13 Validity level and critical stress for I-Bar 77
5.14 Validity level and critical stress for T-Bar 80
xvi
LIST OF GRAPHS
GRAPH NO. TITLE PAGE
5.1 Load vs extension for 0.4m length of I-bar specimen 54
5.2 Load vs extension for 0.6m length of I-bar specimen 55
5.3 Load vs extension for 0.77 m length of I-bar specimen 56
5.4 Load vs extension for 0.4 m length of T-bar specimen 57
5.5 Load vs extension for 0.6 m length of T-bar specimen 58
5.6 Load vs extension for 0.77 m length of T-bar specimen 59
5.7 Comparison graph between experimental and
theoretical for I-bar 66
5.8 Comparison graph between experimental and
theoretical for T-bar 70
5.9 Comparison graph between experimental, theoretical
and error for T-bar 74
5.10 Graph for error data (T-Bar) 75
5.11 Graph stress vs validity level for I bar 78
5.12 Graph stress vs validity level for T bar 81
1
1
INTRODUCTION
1.1 Background
Pultruded fibre reinforced plastic(FRP) composite structural shapes (beams
and columns) are thin walled open or closed sections consisting of assemblies of flat
plates and commonly made of E-glass fibre and either polyester or vinylester resins.
Due to high strength to stiffness ratio of composites and thin walled sectional
geometry of FRP shapes, buckling is the most likely mode of failure before material
failure.
On November 2004, Pizhong Qiao and Luyang Shan are using commercial
finite element program (ANSYS) and shell layered element (SHELL 99) to
determine which plate element either flange or web will buckle first. Besides that,
they compute critical stress resultant (Nx)CT\t in terms of rotational restraint
stiffness(k) for structural shapes like box-, I-, C-, T-, Z- and L- sections. This project
concentrate more on experimental and theoretical in determine the critical load,
stress and validity level rather than software.
Nowadays, FRP composites are widely used as it offer more mechanical and
physical advantages compared to other engineering material. Vinylester resins are
superior in heat resistance, adhesion, corrosion resistance and also mechanical
properties among thermosetting resins and are widely used for coatings, adhesives,
2
electric insulating materials and matrices for fibre reinforced plastic (FRP) in areas
such as aircrafts, electronics electric power and building and civil engineering. The
factors determining the structure of cured resins and affecting the physical and
mechanical properties are as follows:-
a) Curing mechanism : kind of functional groups of hardeners.
b) Number of functional groups in resins and hardeners; density of
crosslinking.
c) Molecular structure of bridges between functional groups in resins
and hardeners.
d) Molar ratio of resin and hardener ; density of crosslinking.
e) Degree of curing or curing conditions.
Slender columns are subject to a type of behavior known as buckling. As
long as the load on such a member is relatively small, increases in the load result
only in an axial shortening of the member. However, once a certain critical load is
reached, the member suddenly bows out sideways. This bending gives rise to large
deformations which in turn cause the member to collapse. The load at which
buckling occurs is thus a design criterion for compression members. Even as simple
a structural element as an axially loaded member behaves in a fairly complex
manner. It is therefore desirable to begin the study of columns with a very idealized
case, the Euler column.
3
1.2 Problem statement
Studies on buckling of Glass Fibre Reinforced Polymer (GFRP) are very
wide and many of them using GFRP with filament wound structure compared to the
pultrusion method. They are more concern with the circular geometry rather to the
T-bar or I-bar geometry and with different orientation alignment angles of fibres.
Knowing that the buckling loads were strongly affected by the fibres orientation and
the stacking sequence, methods which can provide results on other geometry like T-
bar or I-bar and unidirectional fibres are very essential for initial comparison.
Furthermore, the experimental works of filament winding process are mostly
contributed towards the microstructural behaviour and other combination load of
axial compression and superimposed torsion, without concerning on critical load
analysis and validity level. Hence, this research is initiated to provide further
analysis, both theoretical and experimental aspects to the latter cases. Besides that, if
large error produced between theoretical and experimental works, we need to
modify the Euler equation in order to follow the data of experimental value.
1.3 Objective
The objective of this project is to design the test rig that hold the specimen
and to determine the critical load and validity level for GFRP pultruded T-bar/I-bar
under buckling load. From the validity level, we can determine a suitable range of
length that valid under compression or buckling. For this project, we make a
comparison between the theoretical analysis and experiments using Euler column
test method. We need to verify the error and if large error produced between both
experimental and theoretical value, the modification of Euler equation must be done
in order to fix the error so that it will follows the experimental data.