氏名　FARAZILA BINTI YUSOF
学位の種類　博士（工学）
学位記番号　博甲第578号
学位授与の日付　平成23年3月25日
学位論文題目　Study on Dissimilar Material Joining between Polymer and Metals by using Laser Welding and Friction Stir Welding　（レーザー溶接と摩擦撹拌溶接を用いた金属／ポリマー異材接合に関する研究）
論文審査委員
　主査　教授　武藤　睦治
　副査　実務家教授　永田　晃則
　副査　准教授　永澤　茂
　副査　准教授　宮下　幸雄
　副査　産学融合特任講師　大塚　雄市

• 論文目次
• 論文要旨
• 論文審査の結果の要旨

［平成22（2010）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Table of contents

ABSTRACT　p.ii
ACKNOWLEDGEMENT　p.iv
TABLE OF CONTENTS　p.v
LIST OF FIGURES　p.x
LIST OF TABLES　p.xvi
LIST OF PUBLACATIONS　p.xvi

1.INTRODUCTION
　1.1　General background　p.1
　1.2　Polymer　p.2
　1.3　Review of joining techniques　p.3
　1.3.1　Adhesive bonding　p.4
　1.3.2　Mechanical fastening　p.5
　1.3.3　Soldering and brazing　p.6
　1.3.4　Fusion welding process　p.6
　1.3.5　Solid state welding　p.7
　1.4　Polymer and metal joining technologies　p.7
　1.4.1　Laser transmission welding　p.7
　1.4.2　Collar joining　p.9
　1.4.3　Friction riveting　p.10
　1.5　Objectives of this work　p.11
　1.6　Thesis structure　p.12
　References　p.13

2. ND:YAG PULSED LASER JOINING BETWEEN PET AND METALLIC MATERIALS
　2.1　Introduction　p.16
　2.2　Nd:YAG pulsed laser welding　p.17
　2.3　Materials　p.18
　2.4　Experimental procedure　p.21
　2.4.1　Laser joining between PET and metallic materials　p.21
　2.4.2　Adhesive joining between PET and metallic materials　p.21
　2.4.3　Tensile shear test　p.22
　2.4.4　High speed camera observation　p.24
　2.4.5　Temperature distribution　p.24
　2.4.5.1　Thermal modeling simulation　p.24
　2.4.5.2　Temperature measurement　p.26
　2.5　Results and discussion　p.27
　2.5.1　Laser joining between PET/metallic materials joints　p.27
　2.5.1.1　Weldability of PET/metallic materials joints　p.27
　2.5.1.2　Effect of heat input on shear strength　p.28
　2.5.1.3　Cross-sectional observation　p.34
　2.5.2　High speed camera observation（0.72s）　p.37
　2.5.3　Temperature distribution　p.40
　2.5.3.1　Thermal modeling simulation　p.40
　2.5.3.2　Temperature measurement　p.42
　2.6　Joining mechanisms between polymer and metal　p.43
　2.7　Conclusion　p.47
　References　p.48

3.EFFECT OF OXIDE LAYER ON LASER JOINING BETWEEN PET AND CU
　3.1　Introduction　p.50
　3.2　Experimental procedure　p.51
　3.2.1　Experimental setup　p.51
　3.2.2　Pre-deposition process　p.52
　3.2.3　Temperature measurement　p.53
　3.3　Results and discussion　p.54
　3.3.1　Effect of heat input on welded area　p.54
　3.3.2　Effect of heat input on shear strength　p.55
　3.3.3　Cross-sectional observation　p.59
　3.3.4　Temperature measurement　p.60
　3.3.5　Joining mechanism　p.62
　3.4　Conclusion　p.63
　References　p.64

4.EFFECT OF ANODIZING ON PULSED ND:YAG LASER WELDING OF PET/A5052 DISSIMILAR JOINT
　4.1　Introduction　p.65
　4.2　Experimental procedure　p.66
　4.2.1　Experimental setup　p.66
　4.2.2　Temperature measurement　p.68
　4.3　Results and discussion　p.70
　4.3.1　Effect of heat input on welded area　p.70
　4.3.2　Effect of heat input on shear strength　p.70
　4.3.3　Cross-sectional observation　p.74
　4.3.4　Effect of pulse duration under constant heat input　p.76
　4.3.5　Temperature measurement　p.78
　4.4　Conclusion　p.80
　References　p.81

5.DISSIMILAR MATERIALS JOINING BETWEEN A5052 AND PET BY USING FRICTIONAL ENERGY FROM FRICTION STIR SPOT WELDING PROCESS
　5.1　Introdution　p.83
　5.2　Friction stir welding（FSW）　p.84
　5.3　Experimental procedure　p.85
　5.3.1　Experimental setup　p.85
　5.3.2　Temperature measurement　p.88
　5.4　Result and disucssion　p.90
　5.4.1　Effect of plunge speed on joinede area　p.91
　5.4.2　Effect of plunge speed on shear strength　p.92
　5.4.3　Cross-sectional observation　p.96
　5.4.4　Temperature measurement　p.99
　5.4.5　Joining mechanism　p.102
　5.5　Conclusion　p.104
　References　p.105

6.EFFECT OF A5052 SURFACE ROUGHNESS ON JOINING BETWEEN A5052 AND PET BY USING FRICTIONAL ENERGY FROM FRICTION STIR SPOT WELDING PROCESS
　6.1　Introduction　p.106
　6.2　Experimental procedure　p.107
　6.3　Results and discussion　p.110
　6.3.1　Effect of plunge speed on joined area　p.110
　6.3.2　Effect of plunge speed on shear strength　p.111
　6.3.3　Cross-sectional observation　p.119
　6.3.4　Joining mechanism　p.123
　6.4　Conclusion　p.124
　References　p.125

7.OVERALL CONCLUSIONS AND FUTURE RECOMMENDATION
　7.1　General conclusion　p.127
　7.2　Joining mechanism between metal and polymer　p.128
　7.3　Future recommendation　p.129
　References　p.130

A dissimilar material can be defined as a combination of two or more different materials which have unlike physical, mechanical, thermal and chemical properties. The dissimilar material can be formed from combination of metal-metal, metal-polymer, polymer-polymer, metal-ceramic, and so on. Nowadays, many emerging applications such as automobile and aerospace are un-avoidably included dissimilar material joining processes. The joining of dissimilar materials is significantly challenging due to the differences in the material properties. In the dissimilar materials joint, metals are usually selected for applications requiring strength, ductility, thermal conductivity and high machinability. On the other hand, polymeric materials are selected for its formability, corrosion resistance, insulation and lightweight. Since a product usually consists of the assembly of metal and polymer parts, joining of metal and plastic is therefore important from a manufacturing point of view. The suitable joining techniques between metal and polymer could improve assembly process and become useful development for the future of dissimilar materials joining. This thesis includes seven chapters, which are shown below.

Chapter 1 “Introduction”: Chapter one provides an introduction of dissimilar materials joining. This introductory chapter presents the background and motivational for this research. The dissimilar materials joining concept and currently developed joining techniques are discussed as well. Then the objective and scope of this work are addressed.

Chapter 2 “Nd: YAG pulsed laser joining between PET and metallic materials”: In this chapter, the experimental results of direct laser joining using Nd: YAG laser spot welding between polyethylene terephthalate （PET） and metallic materials were presented. The experimental result showed polyethylene terephthalate （PET） could be successfully joined to aluminum alloy （A5052）, stainless steel （SUS 304） and copper （C1220P）. Shear tensile test was carried out to evaluate the shear strength. In the case of PET/C1220P joint, the shear strength was almost constant regardless of heat input. However, the strength increased with increasing heat input for PET/A5052 and PET/SUS304 joints. Cross-sectional observation of the joined specimen showed no significant molten pool in the case of PET/Cu joint. On the other hand, an obvious weld pool was observed at the interface in metallic material side for PET/A5052 and PET/SUS304 joints. Differences of morphology at the interface would result from different material properties, such as reflectivity and absorptivity of laser, thermal conductivity, etc., of metallic materials used and might affect the joining strength.

Chapter 3 “Effect of oxide layer on laser joining between PET and Cu” : In the present chapter, the laser welding experiments between polyethylene terephthalate （PET） and copper （C1220P） were performed to investigate the oxide layer effect on copper surface. The experimental result for PET/C1220P joint with pre-oxide layer exhibit higher shear strength compared to and PET/C1220P joint without pre-oxide layer. The results showed the pre-oxidation surface improved the welding efficiency and high heat was absorbed during laser irradiation. On the other hand, the fracture surface of PET/C1220P with pre-oxide showed the presence of copper and copper oxide particles in the PET side. However in the case of PET/C1220P without pre-oxide, no occurrence of Cu particles can be observed.

Chapter 4 “Effect of anodizing on pulsed Nd: YAG laser welding of PET/A5052 dissimilar joint” : A series of laser welding experiments between polyethylene terephthlate （PET） and aluminum alloy （A5052） were conducted to investigate anodizing effect on A5052 surface in the dissimilar joint. The anodization process could improve shear strength of the laser welded joints. PET/A5052 welded joints with A5052 anodizing surface exhibited greater joining strength compared to PET/A5052 welded joints without anodizing on A5052 surface. In addition the joining strength increased with increasing heat input and pulse duration. Significant molten pools were formed in both PET/A5052 （anodized） and PET/A5052 （as-received） joints except for PET/A5052 （as-received） joint welded at the lowest heat input and pulse duration. From the test results under different pulse duration at the constant heat input, it could be confirmed that joining behavior was dominantly controlled by heat input not by pulse duration.

Chapter 5 “Dissimilar materials joining between A5052 and PET by using frictional energy from friction stir spot welding process” : In this chapter another joining process was proposed to join metal and polymer. The frictional energy generated from friction stir spot welding （FSSW） process was utilized for joining dissimilar materials. An aluminum alloy （A5052） and polyethylene terephthalate （PET） were chosen as a dissimilar material pair. The experimental results showed A5052 and PET could be joined using frictional energy. Good bonding between PET and A5052 was achieved and significant bubbles were formed in the PET. According to the temperature measurement, the maximum peak temperature of 331℃ was occurred and this value was above the melting temperature of PET. It was believed that, during welding process, the PET was melted and these molten PET was tightly stick on the A5052 surface and induced good mechanical bonding.

Chapter 6 “Effect of A5052 surface roughness on joining between A5052 and PET by using frictional energy from friction stir spot welding process” : Friction stir spot welding experiments were carried out for dissimilar materials joining between aluminum alloy （A5052） and polyethylene terephthalate （PET） to study the effect of surface roughness on the A5052 surface. Generally, the A5052/ PET joint with various surface roughness level exhibited excellent joining strength compared to A5052/PET joint as-received specimen. The maximum shear strength obtained was around 9.03 MPa and this value was higher than laser bonded specimens. The cross-sectional observation showed the PET penetrated inside the irregular A5052 surfaces for the A5052/PET joint with surface modification. It is believed that strong mechanical bonding （anchor effect） between A5052 and PET would be occurred for the joined specimens with surface modification.

Chapter 7 “Overall conclusions” : Based on the above results and discussion, two different dissimilar joining techniques for joining between metal and polymer were summarized. The significant research results in the dissimilar materials joining were described. Future researches to be developed were also suggested.

　 本論文は、「Study on Dissimilar Material Joining between Polymer and Metals by using Laser Welding and Friction Stir Welding」と題し、７章より構成されている。
　第１章「Introduction」では、異材接合法に関する従来の研究の概要を示すとともに、本研究の目的と範囲を述べている。
　第２章「Nd:YAG pulsed laser joining between PET and metallic materials」では、PETとアルミニウム合金、ステンレス鋼および銅とのレーザー接合を試み、接合特性を調べ、PET/アルミニウム合金、PET/ステンレス鋼では接合界面近傍で溶融が生じ、良好な接合が生じるが、PET/銅では溶融が生じず、強度も低いこと、それが金属材料の熱伝導特性に依存していることなどを明らかにしている。
　第３章「Effect of oxide layer on laser joining between PET and Cu」では、銅の接合表面に酸化膜を形成し、レーザーエネルギーを局所的に吸収することにより、接合界面での局所的溶融を生じさせることができ、PET/銅の接合強度を改善できることなどを明らかにしている。
　第４章「Effect of anodizing on pulsed Nd:YAG laser welding of PET/A5052 dissimilar joint」では、アルミニウム合金の接合表面に陽極酸化処理を施すことにより、接合界面近傍でのレーザーエネルギーの吸収効率が格段に高くなり、PET/アルミニウム合金の接合強度をさらに向上させることができることなどを明らかにしている。
　第５章「Dissimilar materials joining between A5052 and PET by using frictional energy from friction stir spot welding process」では、摩擦撹拌の発熱を利用したPETとアルミニウム合金の接合を試み、接合界面近傍の温度がPETの融点より十分高く、溶融させることができ、接合が可能なことを明らかにしている。
　第６章「Effect of A5052 surface roughness on joining between A5052 and PET byusing frictional energy from friction stir spot welding process」では、アルミニウム合金の接合表面のエッチング等の方法により表面粗さを変化させ接合すると、表面粗さの粗い方が、機械的アンカー効果との相乗効果で、より高い接合強度が得られることなどを明らかにしている。
　第７章「Overall conclusions」では、以上得られた結果を総括し、ポリマーと金属との異材接合の今後の課題について示している。
　よって、本論文は工学上及び工業上貢献するところが大きく、博士（工学）の学位論文として十分な価値を有するものと認める。