氏名　BOONYAPOOKANA ALISA
学位の種類　博士（工学）
学位記番号　博甲第605号
学位授与の日付　平成23年9月30日
学位論文題目　Fatigue crack growth behavior of silica particle reinforced epoxy resin composite　（シリカ粒子強化エポキシ複合材料の疲労き裂伝ぱ挙動）
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　教授　井原　郁夫
　副査　准教授　宮下　幸雄
　副査　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23（2011）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.viii
List of Tables　p.xi

Chapter1　INTRODUCTION
　1.1　Epoxy resin reinforced composite　p.2
　1.2　Introduction to fatigue crack growth　p.3
　1.2.1　Fatigue crack growth test　p.3
　1.2.2　Crack tip shielding mechanisms　p.6
　1.2.3　Problem statement　p.10
　1.3　Literature review　p.12
　1.3.1　Fatigue crack growth　p.12
　1.3.2　Effect of frequency　p.13
　1.3.3　Crack growth behavior　p.14
　1.4　Research motivation and objectives　p.15
　1.5　Dissertation outline　p.17
　References　p.19

Chapter2　Effect of R-ratio on fatigue crack growth bhavior in silica particle reinforced epoxy resin composite
　2.1　Introduction　p.23
　2.2　Experimental procedures　p.24
　2.2.1　material　p.24
　2.2.2　Fatigue crack growth specimen　p.27
　2.2.3　Fatigue crack growth test　p.27
　2.3　Results and discussion　p.29
　2.3.1　Fatigue crack growth curve　p.29
　2.3.2　Fracture surface observations　p.33
　2.4　Conclusions　p.39
　References　p.40

Chapter3　Effect of R-ratio on fatigue crack growth behavior in pure epoxy resin
　3.1　Introduction　p.44
　3.2　Experimental procedures　p.45
　3.2.1　Material　p.45
　3.2.2　Fatigue crack growth specimen　p.45
　3.2.3　Fatigue crack growth test　p.46
　3.3　Results and discussion　p.47
　3.3.1　Fatigue crack growth curve　p.47
　3.3.2　Fracture suface observations　p.52
　3.4　Conclusions　p.56
　Reference　p.58

Chapter4　Fatigue crack propagation mechanism in silica particle reinforced epoxy resin composite
　4.1　Introduction　p.60
　4.2　Experimental procedures　p.61
　4.2.1　Material　p.61
　4.2.2　Fatigue test specimen　p.61
　4.2.3　In-situ observation of crack propagation behavior　p.62
　4.3　Results and discussion　p.63
　4.3.1　Fatigue crack growth curve　p.63
　4.3.2　Crack growth mechanisms　p.68
　4.3.3　Fracture surface observations　p.70
　4.3.4　Stress distribution analysis　p.73
　4.4　Conclusions　p.77
　Reference　p.79

Chapter5　Fatigue crack growth behavior under Kmax constant condition with different R-ratios in silica particle reinforced epoxy resin
　5.1　Dependence of optimal parameters on discharge gap　p.83
　5.2　Dependence of optimal parameters on applied voltage　p.84
　5.2.1　Material　p.84
　5.2.2　Fatigue test specimen　p.84
　5.2.3　Fatigue crack growth test　p.85
　5.3　Results and discussion　p.87
　5.3.1　Fatigue crack growth curve　p.87
　5.3.2　Crack growth mechanisms　p.91
　5.3.3　Fracture surface observations　p.92
　5.4　Conclusion　p.98
　Reference　p.99

Chapter6　Effect of frequency on fatigue crack growth behavior under Kmax constant in silica particle reinforced epoxy resin composite
　6.1　Introduction　p.101
　6.2　Experimental procedures　p.102
　6.2.1　Material　p.102
　6.2.2　Fatigue test spesimen　p.102
　6.2.3　Fatigue crack growth test　p.103
　6.3　Results and discussion　p.105
　6.3.1　Fatigue crack growth curve　p.105
　6.3.2　Crack growth mechanisms　p.109
　6.3.3　Fracture surface observations　p.115
　6.4　Conclusions　p.125
　Reference　p.126

Chapter7　General conclusions
　7.1　General conslusion　p.128
　7.2　Recommendations for future work　p.130

　Epoxy resin composites are being used increasingly in many applications due to the outstanding properties compare to the other type of polymer composites. They are attractive in a structural components design. During services, these components usually encounter many factors such as loading cycle, mean stress, frequency, and temperature. Under these conditions, crack during service can be initiated and grow rapidly. These cracks often lead to catastrophic failure. Therefore, in order to prevent the failure under service conditions, fracture mechanics approach was applied to estimate the fatigue life in the composite material. Moreover, it is known that in composite materials, failure usually takes place at the bonded interfaces, often involving microcracking, particle debonding, etc. Therefore, it is important to understand the fatigue crack growth behavior as well as crack propagation mechanism of the epoxy resin composites.

Chapter 1 Introduction: An introduction of epoxy resin composite as well as the fracture mechanics approaches using in this research have been describes. A brief literature review on fatigue crack growth and fatigue crack propagation behavior of the present composite is also described. Problem statement undertaking the present study has been presented.

Chapter 2 Effect of R-ratio on fatigue crack growth behavior in silica particle reinforced epoxy resin composite: The fatigue crack growth tests of the epoxy resin composite reinforce with silica particle were carried out under various R-ratios. The fatigue crack growth test results indicated that the crack growth curved arrange by ΔK showed clear R-ratio dependence even under no crack closure effect while crack growth curve arranged by Kmax merged into almost one curve which indicated that Kmax was controlled the fatigue crack growth behavior in the present composite and dominate by time-dependent.

Chapter 3 Effect of R-ratio on fatigue crack growth behavior in pure epoxy resin: In this chapter, fatigue crack growth under various R-ratios of pure epoxy resin was performed in order to clarify the crack growth behavior of matrix which is used in the present composite. The experimental results showed that the fatigue crack growth of pure epoxy resin exhibited same characteristic as the present composite which is dominantly time-dependent and controlled by Kmax. Moreover, reinforced particle was found to increase the threshold value in the present composite compare with the pure epoxy resin.

Chapter 4 Fatigue crack propagation mechanism in silica particle reinforced epoxy resin composite: As observed from the previous chapter, it was found that reinforced particle enhanced the fatigue crack growth rate. Therefore in this chapter the fatigue crack growth behavior of the present composite was investigated under ΔK constant. SEM in situ observation was carried out in order to understanding the crack propagation process in the present composite. The results showed that in the present composite, microcrack always nucleated ahead of the main crack tip between the interface near the matrix/particle and then propagate to coalesce with the main crack. Retardation of crack growth rate was found from the crack bridging induced by microcracking and crack deflection by reinforced particles.

Chapter 5 Fatigue crack growth behavior under Kmax constant condition with different R-ratios in silica particle reinforced epoxy resin composite: From the result in Chapter 2, it has been found that Kmax was the factor that dominated the fatigue crack growth behavior in the present composite. Therefore in this chapter, Kmax constant test was carried out in order to confirm that Kmax dominated the crack growth in the present composite. The fatigue crack growth under 2 levels of Kmax was conducted with various R-ratios. The results showed that the crack growth rate under Kmax constant was independent with R-ratio as indicated in Chapter 2.

Chapter 6 Effect of frequency on fatigue crack growth behavior under Kmax constant in silica particle reinforced epoxy resin composite: In this chapter, to understand more detailed about the fatigue crack growth in the present composite, effect of frequency was also conduct under Kmax constant test with various R-ratios. The results showed the fatigue crack growth rate arranged by da/dN, was increasing when decreasing in frequency while crack growth rate became constant for all cases regardless of frequency when arranged by da/dt. This indicates that crack growth behavior of the present composite is time-dependent.

Chapter 7 General conclusion and future work: The conclusions of the current work were summarized. Recommendation for future work was also presented.

　本論文は、「Fatigue crack growth behavior of silica particle reinforced epoxy resin composite（シリカ粒子強化エポキシ複合材料の疲労き裂伝ぱ挙動）」と題し、7章より構成されている。
第1章「Introduction」では、粒子強化複合材料の諸特性について述べるとともに、複合材料の疲労の研究に関する現状と問題点について述べるとともに、本研究の目的と範囲を述べている。
　第2章「Effect of R-ratio on fatigue crack growth behavior in silica particle reinforced epoxy resin composite」では、シリカ粒子強化エポキシ複合材料の疲労き裂伝ぱの基本特性と応力比の影響について調べ、本複合材料の疲労き裂伝ぱが、これまで扱われているΔKではなくKmaxにより支配されており、Kmaxでき裂伝ぱ曲線を整理することにより応力比によらない一本の伝ぱ曲線が得られることなどを明らかにしている。
　第3章「Effect of R-ratio on fatigue crack growth behavior in pure epoxy resin」では、前章で明らかにしたKmax依存のき裂伝ぱ特性がエポキシ母相のき裂伝ぱ特性に依存するものかどうかを明らかにするため、エポキシの疲労き裂伝ぱ特性を調べ、そのき裂伝ぱ特性がやはりKmaxに支配され、Kmaxで整理することにより応力比に依存しない一本のき裂伝ぱ曲線で整理できること、粒子強化により、き裂伝ぱ抵抗が向上していることなどを明らかにしている。
　第4章「Fatigue crack propagation mechanism in silica particle reinforced epoxy resin composite」では、本複合材料の疲労き裂伝ぱのその場観察を行い、き裂前方で粒子と母相の境界近傍で微小き裂が発生し、それが主き裂と連結することを繰り返し、進展すること、大きな粒子にはき裂が潜在しており、それを経由してき裂が進展する場合のあることなどを明らかにしている。
　第5章「Fatigue crack　growth　behavior　under　Kmax　constant　condition　with　different　R-ratio　in　silica　particle　reinforced epoxy resin composite」では、Kmax一定下でKminを様々に変化させた試験を行い、Kminに全く依存しないKmax支配のき裂伝ぱ挙動を示すことなどを明らかにしている。
第6章「Effect of　frequency　on　fatigue　crack　growth　behavior　under　Kmax　constant　in　silica　particle　reinforced　epoxy resin composite」では、繰返し周波数を大幅に変化したKmax一定の試験を行い、き裂伝ぱ速度が、繰返し速度によらずKmaxで整理でき、き裂伝ぱがKmax支配であり、時間依存の挙動を示すことなどを明らかにした。
第7章「General conclusions」では、本論文で得られた結論を要約するとともに、本論文に基づき、今後の展開についても論じている。
　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。