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UNIVERSITI PUTRA MALAYSIA

DESIGN AND ANALYSIS OF FILAMENT- WOUND COMPRESSED NATURAL GAS CARBON FIBRE - REINFORCED

COMPOSITE TANK

NURUL ZUHAIRAH MAHMUD ZUHUDI

FK 2008 33


COMPOSITE TANK


MASTER OF SCIENCE UNIVERSITI PUTRA MALAYSIA

2008


COMPOSITE TANK

By


Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Master of

Science

May 2008

DEDICATION

Especially to Abah, Hj. Mahmud Zuhudi Tahir and Umi, Hjh. Kamariah

Mohd Noor…this is my special gift to both of you. To my beloved

husband, Mohd Azan Che Noh, kakak (Nurul Izzati Amali) and abang

(Muhammad Ameerul Wajdi), they have been and will be my

inspiration…

ABSTRACT Abstract of thesis presented to the Senate of Universiti Putra Malaysia in

fulfilment of the requirement for the degree of Master of Science

DESIGN AND ANALYSIS OF FILAMENT - WOUND COMPRESSED NATURAL GAS CARBON FIBRE - REINFORCED

COMPOSITE TANK

By


May 2008

Chairman: Professor Fakhru’l-Razi Ahmadun, PhD

Faculty: Faculty of Engineering

First ply failure (FPF) strengths of laminated composite tank subjected to

uniform internal pressure loads are studied via both analytical and finite

element analysis approaches. The filament-wound CNG carbon fibre

reinforced composite tanks are designed with a T6-6061 aluminium

cylinder with elliptical end closures acts as the liner which is over-

wrapped with high modulus carbon fibre-reinforced epoxy composite.

The objectives of this study are to optimize the composite layer

thickness and to optimize fibre orientation configurations of carbon fibre

laminate as to have a lightweight and high performance filament-wound

CNG carbon fibre-reinforced composite tanks. In analytical approaches,

in order to predict the first-ply failure (FPF) pressure of filament-wound

CNG carbon fibre-reinforced composite tanks, the stresses and strains

throughout the laminate were determined using the classical lamination

theory which were then used in three most common composite failure

theories, that are the maximum stress theory, maximum strain theory,

and quadratic or Tsai-Wu failure theory.

Optimal general design of fibre orientations were then used to carry out

in lay-up optimization or arrangement of composite layer stage to be

used for filament winding process in order to study the effect of fibre

orientation angles using an equal thickness of composite layer on the

tank performance. The range of helical angles used is in between 0° to

60°, which is based on the traditional theoretical optimal helical angles

from classical lamination theory. The ratio of 2:1 hoop to helical angles is

used to predict the maximum first-ply failure (FPF) pressure.

The optimization results gave the optimal fibre orientations of the

( )[ ]2411 90/30/30 − with b/a = 1.093 for CNG 1, b/a = 1.110 for CNG 2 and

b/a = 1.128 for CNG 3 which obtained were then used for stress analysis

in finite element analysis using ANSYS version 7.1 software. The

accuracy of the theoretical and finite element analysis of first-ply failure

(FPF) pressure is verified by a verification study where a similar finite

element model from literature have been modelled and analysed using

similar method used to design filament wound CNG carbon fibre-

reinforced composite tanks in order to verify a valid finite element

method used. The results were then being compared literature study.

ABSTRAK Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia

sebagai memenuhi keperluan untuk ijazah Master Sains

REKA BENTUK DAN ANALISIS TANGKI KOMPOSIT FILAMEN BERLILIT BERISI GAS ASLI MAMPAT DENGAN GENTIAN KARBON

DIPERKUKUHKAN

Oleh


May 2008

Pengerusi: Professor Fakhru’l-Razi Ahmadun, PhD

Fakulti: Fakulti Kejuruteraan

Kegagalan lapisan pertama (FPF) kekuatan-kekuatan tangki komposit

yang berlapis bawah muatan-muatan tekanan dalaman yang seragam

adalah dikaji melalui analisis kedua-dua pendekatan iaitu analitikal dan

analisis unsur terhingga. Tangki-tangki komposit filamen berlilit gentian

karbon CNG yang diperkukuhkan direka bentuk dengan satu silinder

aluminium T6-6061 dengan penutupan akhir yang bujur berfungsi

sebagai lapisan dalaman yang akan dibungkus besar dengan gentian

karbon bermodulus tinggi yang diperkukuhkan dengan rencam epoksi.

Objektif-objektif kajian ini adalah untuk mengoptimumkan ketebalan

lapisan komposit dan untuk mengoptimumkan orientasi gentian

konfigurasi-konfigurasi lapis gentian karbon sebagai untuk menghasilkan

tangki-tangki komposit berfilamen berlilit gentian karbon CNG yang

diperkukuhkan yang ringan dan berprestasi tinggi. Dalam pendekatan-

pendekatan analisis, untuk meramalkan tekanan bagi kegagalan lapisan

pertama (FPF) tangki-tangki komposit berfilamen gentian karbon CNG

yang diperkukuhkan, tekanan dan terikan sepanjang lapis adalah

ditentukan menggunakan teori pelapisan klasik yang telah kemudiannya

digunakan dalam tiga rencam paling popular dalam teori-teori

kegagalan, yang adalah teori tegasan maksimum, teori keterikan

maksimum, dan kuadratik atau teori kegagalan Tsai-Wu.

Corak umum optimum orientasi-orientasi gentian adalah kemudian

digunakan bagi menjalankan dalam mengumpul pengoptimuman atau

susunan peringkat lapisan komposit teratur untuk digunakan dalam

proses lilitan filamen bagi mengkaji kesan sudut-sudut orientasi gentian

menggunakan ketebalan yang sama rata lapisan tangki komposit. Julat

sudut-sudut berlingkar digunakan adalah dalam antara 0° to 60°, yang

adalah diasaskan ketradisionalan sudut-sudut yang berlingkar teori dan

optimum daripada teori pelapisan klasik. Nisbah 2:1 gelung untuk sudut-

sudut berlingkar adalah digunakan untuk meramal maksimum tekanan

kegagalan lapisan pertama (FPF).

Hasil-hasil pengoptimuman memberi orientasi-orientasi gentian optimum

( )[ ]2411 90/30/30 − dengan b/a = 1.093 untuk CNG 1, b/a = 1.110 untuk

CNG 2 dan b/a= 1.128 untuk CNG 3 yang diperolehi adalah

kemudiannya digunakan untuk analisis tegasan dalam analisis unsur

terhingga menggunakan perisian ANSYS versi 7.1. Ketepatan analisis

teori dan analisis unsur terhingga bagi tekanan kegagalan lapisan

pertama (FPF) disahkan oleh satu pengesahan kajian di mana satu

elemen terhad serupa daripada maklumat kajian bertulis terdahulu telah

dijadikan contoh dan dianalisis menggunakan kaedah serupa digunakan

untuk mereka tangki-tangki komposit berfilamen berliku gentian karbon

CNG yang diperkukuhkan untuk mengesahkan satu kaedah unsur

terhingga yang tepat digunakan. Hasilnya adalah kemudian

dibandingkan dengan kajian terdahulu.

ACKNOWLEDGEMENTS

One page to acknowledge all those who encouraged, inspired, and hung

out with the author during her stay at UPM... my 1st supervisor, Dr. El

Sadig Mahdi for his guidance and generous support and also for his

solid, logical suggestions for conquering obstacles, instead of his casual,

nurturing relationship that allowed some of my rather abstract and often

harebrained ideas to mature into interesting scientific questions. Indeed

his moral and kind guidance was one in a kind.

The author also extend her gratitude to Prof. Fakhru’l-Razi Ahmadun,

her current supervisor, Dr. Mohd Amran and his team (Fuel Storage

Team) which she deeply indebted to them for their help in so many

aspects of her work and life. The author would like to thank her friends

and lab mates, past and present, for their collaboration as colleagues

and support as friends.

Finally, and most importantly the author would like to thank her family

particularly her parents, for the obvious reasons (i.e., her birth) and for

their enthusiastic support. The author’s brothers and sisters get credits

for they lifted her up when she could not reach. They are the ones who

held her up and never let she fall. And last but not least, especially for

the author beloved husband, Mohd Azan, her child Izzati Amali and

Ameerul Wajdi , they have been and will be her inspiration…………

I certify that an Examination Committee met on 28 May 2008 to conduct the final examination of Nurul Zuhairah Mahmud Zuhudi on her Master Science thesis entitled “Design and Analysis Of Filament-Wound Compressed Natural Gas Carbon Fibre-Reinforced Composite Tank” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Robiah Yunus, Ph.D. Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Mohd Sapuan Salit, Ph.D. Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Mohamed Tarmizi Ahmad, M.Sc. Lecturer Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Che Hassan Che Haron, Ph.D. Professor Faculty of Engineering Universiti Kebangsaan Malaysia (External Examiner) ___________________________ HASANAH MOHD. GHAZALI, Ph.D. Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master Science. The members of the Supervisory Committee were as follows: Prof. Fakhru’l-Razi Ahmadun, PhD Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Dr. Mohd Amran Mohd Salleh, PhD Faculty of Engineering Universiti Putra Malaysia (Member) Dr. Mohd Rizal Zahari, PhD Faculty of Engineering Universiti Putra Malaysia (Member) Dr. El Sadig Mahdi Ahmed Saad, PhD Faculty of Engineering International Islamic University Malaysia (Member) ______________________ AINI IDERIS, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date: 14th August 2008

DECLARATION I declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or is not concurrently, submitted for any other degree at UPM or other institutions. _____________________________ NURUL ZUHAIRAH BINTI MAHMUD ZUHUDI Date: 10th July 2008

TABLE OF CONTENTS

Page

ABSTRACT iii ABSTRAK Vi ACKNOWLEDGEMENTS ix APPROVAL X DECLARATION xii LIST OF FIGURES xvi LIST OF TABLES xix LIST OF ABBREVIATIONS xxii CHAPTER

1 INTRODUCTION 1 1.1 Introduction

1.2 Problems Statement 1.3 Scope of Work 1.4 Objectives 1.5 Thesis Layout

1 2 3 4 4

2 LITERATURE REVIEW

2.1 Composite Pressure Vessels 2.2 Compressed Natural Gas Storage 2.3 First-Ply Failure 2.4 Composite Failure Theories 2.5 Fibre Orientations Angle Optimization 2.6 Filament Winding Process 2.7 Fabrication of Filament Wound CNG Carbon Fibre

Reinforced Composite Tank 2.8 Finite Element Analysis 2.9 Composite Materials 2.10 Conclusion

7 20 22 25 30 31

35 41 42 51

3 MATERIALS AND METHODS

3.1 Introduction 3.2 Design Methodology

3.2. 1 Modelling of Problem 3.2. 2 Analytical Analysis 3.2. 3 Optimization of Composite Strength 3.2. 4 FEA of Composite Tank

3.3 Design Configuration 3.4 Material and Mechanical Properties 3.5 Analytical Analysis

3.5. 1 Introduction 3.5. 2 Methodology

52 53 54 56 56 56 57 60

61 61

3.5. 3 Design Formulation 3.5. 4 Elastic Analysis 3.5. 5 Initial Yielding of Liner 3.5. 6 Post-yield Overpressure 3.5. 7 Pressure at Failure 3.5. 8 Residual Stress

3.6 Optimization of Composite Strength 3.6. 1 Introduction 3.6. 2 Methodology

63 64 68 69 70 72

75 75

4 RESULTS AND DISCUSSION

4.1 Analytical Analysis Results 4.1. 1 Result of Theoretical Stresses and Strains 4.1. 2 First Ply Failure Analysis of Filament

Wound CNG Carbon Fibre Reinforced Composite Tanks

4.2 Optimization Results 4.2. 1 Effect of the Fibre Orientation Angle 4.2. 2 CNG 1 4.2. 3 CNG 2 4.2. 4 CNG 3 4.2. 5 Lay-up Optimization

4.3 Conclusion

80

82

84 85 90 95 99

100

5 FINITE ELEMENT ANALYSIS 5.1 Introduction 5.2 Methodology

5.2.1 Modelling 5.2.2 Meshing 5.2.3 Material Properties 5.2.4 Solution Phase 5.2.5 Verification Study

5.3 Result and Discussion 5.3.1 Element Optimization 5.3.2 Composite Stress Analysis 5.3.3 Analysis Tank Cross Section

5.4 Final Design for Fabrications Procedure 5.4.1 Introduction 5.4.2 Tank Sizing 5.4.3 Weight Distribution

102 102 105 107 109 109 111

113 120 123

124 124 125

6 SUMMARY, CONCLUSION AND RECOMMENDATIONS

FOR FUTURE RESEARCH

127 REFERENCES 131 APPENDICES 136 BIODATA OF THE STUDENT 159

LIST OF FIGURES

Figure Page

2.1 The Design and Atmospheric Pressure and Temperature according to the Code Definition adopted from Hoa [22]

20

2.2 A Basic Filament Winding Technique (Adopted from Shen [35])

32

2.3 Figure 2.3: The Type of Winding angle from Shen [35]

39

2.4 Principal Axes of the Composite and the Corresponding Elastic Constant

49

3.1 Flow Chart of Research Methodology 53

3.2 CNG 3 Tank Placement 58

3.3 CNG 1 and CNG 2 Tank Placement 58

3.4 Free-Body Diagram of Relating Pressure Drop across the Liner and the Hoop Stress in the Liner from Swanson [49]

68

3.5 Liner Hoop Stress as a Function of Pressure in a CNG Tank with Liner Reinforced by a Composite Over Wrap from Swanson [49]

74

3.6 Flow Chart of Optimization Method

76

3.7 Cylindrical Cross Section of Tank 78

4.1 First Ply Failure (FPF) Pressures (MPa) versus Helical Angles (Deg)

83

4.2 FPF Pressures of Optimal Winding Angles at ( )[ ]2411 90/30/30 − for Three Failure Theories using

b/a = 1.093

87


b/a = 1.110

92


b/a = 1.128

96

5.1 The Flow Chart of Finite Element Analysis Procedures

104

5.2 Finite Element Grid of Filament Wound CNG Pressure Tank with Aluminium Liner

106

5.3 The Element of Shell99

108

5.4 The Boundary Condition used in the FEA

110

5.5 The Final Model after Applied Loading Condition to be Submitted for Solving Analysis

111

5.6 Stress Distribution through the Thickness at the Mid-Length of the verification of SAUVIM model

112

5.7 Strain Distribution through the Thickness at the Mid-Length of the verification of SAUVIM model.

113

5.8 The Finite Element Grid of CNG Tank with various Global Element

117

5.9 Maximum Radial and Hoop Strain Distribution for Global Element Size.

117

5.10a Maximum Radial Stress Distribution for Global Element Size.

118

5.10b Maximum Hoop Stress Distribution for Global Element Size

118

5.10c Maximum Axial Stress Distribution for Global Element Size.

118

5.11a Maximum Radial and Hoop Stress Distribution for Element Shape of Quadratic and Triangle element.

119

5.11b Maximum Radial and Hoop Strain Distribution for Element Shape of Quadratic and Triangle element.

119

5.12 The Radial, Hoop and Axial Stress Distribution at the Mid Length through the Thickness.

121

5.13 The Radial, Hoop and Axial Strain Distribution at the Mid Length through the Thickness.

122

5.14 A Cross Section Layout for FPF Predictions

123

LIST OF TABLES

Table PAGE 3.1 CNG Composite Tank Design Requirements 59 3.2 CNG Tank Design Configurations 59 3.3 The Composite Thickness and b/a ratio for a

Given Configuration used to Investigate the Effect of FPF Pressure for CNG 1

78

3.4 The Composite Thickness and b/a ratio for a Given Configuration used to Investigate the Effect of FPF Pressure for CNG 2

78

3.5 The Composite Thickness and b/a ratio for a Given Configuration used to Investigate the Effect of FPF Pressure for CNG 3

79

4.1 Theoretical Result of the Stress Strain Predictions using Formulation

80

4.2 FPF Pressures for Three Failure Theories for each Lamination Arrangement of Fibre Orientation

84

4.3 FPF Pressures of Optimal Winding Angles for Three Failure Theories using b/a = 1.039

87

4.4 FPF Pressures of Optimal Winding Angles for Three Failure Theories using b/a= 1.049

88


88


88


89


89


92


93


93


93


94


94


96


97


97


98


98


98

4.21 FPF Pressures (MPa) of Optimal Winding Angles ( )[ ]2411 90/30/30 − for Three Failure Theories of CNG 1

99


100


100

5.1 The Geometric Dimension and Design Pressure of Finite Element Grid of CNG Composite Tank for CNG 1

106

5.2 The Total Nodes and Elements Developed For 115

Each Global Element Size.

5.3 The Maximum Stress and Strain Level at different temperature at TsaiWu Failure Criteria

118

5.4 Tank Sizing Configuration of CNG Composite Tanks

125

5.5 Weight Estimation of CNG Composite Tanks

126

LIST OF ABBREVIATIONS

List Page

1σ Stress in x direction 48

2σ Stress in y direction 48

12τ Tau in 1-2 direction 48

TX Tension in x-direction 48

CX Compression in x-direction 48

TY Tension in y-direction 48

CY Compression in y-direction 48

S Inverse of the stifness matrix 48

1ε Epsilon 1 direction 48

2ε Epsilon 2 direction 48

12γ Gamma 1,2 direction 48

iF Force initial 50

ASTEB Advanced test evaluation bottle 23

Q Stiffness matrix 49

11E Axial parallel elastic modules 48

12E Transverse elastic modules 48

12υ Poisson’s ratio 48

12G Shear Modules 48

R Tensor strain 51

T Tensor rotation 51

θ Fibre orientation angle 47

Q The elastic properties of composite at arbitrary angle to the fibres

52

β Cone vertex angle 74

δ Transverse deformation 74

FEA Finite Element Analysis 106

CHAPTER 1

INTRODUCTION

1.1 Introduction

Known pressure vessels that can operate at high pressures include all

metallic vessels. An all-metallic vessel which would satisfy the strength

requirements for operating at high pressures generally requires high

grade steel whose cost makes commercial production of such vessels

unfeasible. Filament-wound composite pressure tanks, which utilize a

filament winding fabrication technique to form high strength and light

weight reinforced plastic parts, are a major type of high pressure vessels

and are widely used in commercial and aerospace industries such as

fuel tanks, and rocket motor cases as reported by Shen [35].

Due to the rapid development of material science, the composite

material industry has been growing at a dramatic pace in order to meet

the challenges of the future. The lightweight, high strength and high

performance composite structures can offer a significant weight savings

over their traditional metal parts studied by Chang [26].

Continuous filament winding has provided opportunities for designers to

gain the ultimate strength out of materials and to efficiently place

materials where is needed. The successful development of filament-

wound pressure tanks with metal liner has provided significant weight

savings over the conventional metal pressure tanks. The basic concepts

of this design is to use a thin metallic liner designed mainly as

permeation barrier with little load carrying capacity capability, while the

composite is sized to carry all the pressure loads. Therefore, the weight

savings can be derived from the dramatic difference in specific strength

between metal and composite. The leaks before burst or rupture

characteristics of the filament-wound metal lined pressure vessel further

enhance the safety of the overall system.

1.2 Problem Statement

Among present known fuels natural gas is one of the cheapest, the most

environmentally friendly and provides the highest safety margin during

operation. The most important component of natural gas fuel systems is

the compressed natural gas (CNG) storage tank. The high-pressure tank

must safely (statically) withstand, without leakage or cracking, the

maximum operational pressure and fatigue load cycles resulting from

recharging. The problems or issues involved in the design and analysis

of a filament-wound composite tank is to optimise composite layer

thickness and optimise fibre orientation configuration of composite

laminated in order to have high pressure tank.

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