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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

APPENDIX I

APPENDIX II

APPENDIX III

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.