Experimental and Numerical Investigation on the Structural Principles of Polymer Electrolyte Membrane Fuel Cell and Its Components

Experimental and Numerical Investigation on the Structural Principles of Polymer Electrolyte Membrane Fuel Cell and Its Components
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Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices which convert the chemical energy of reactants directly into electrical energy. This technology enables high efficiency and high energy density compared to internal combustion engines and current batteries, thereby making the technology attractive for broad range of applications. Furthermore, the only exhaust from PEMFCs is water, which makes them favorable from the environmental point of view. The commercial success of PEM fuel cell depends on durability, stability, and reliability issues associated with the cell layers among which mechanical durability is still open for investigation on a much broader class. The power density of PEM fuel cell largely depends upon the coupled electro-chemical and electro-mechanical optimal functioning of the membrane electrode assembly (MEA). As the researches on innovative materials for fuel cell is advancing with a rapid pace, it is always necessary to lay a foundation based on the structural integrity and to relate this with the cell performance and functioning. Hence, the objective of this research is to investigate the structural integrity principles of a single PEM fuel cell stack and its layers through combined experimental and numerical techniques. The experimental investigation includes the fabrication of the catalyst layers (CLs), the nano-mechanical property extractions of the CLs and the carbon fibers (CFs), artificial chemical degradation of the membranes, and the physical characterization. The findings of this research suggest the dependency of mechanical properties on the material heterogeneities associated with the CLs and CFs. The surface roughness evolution and surface morphology changes in the membrane are observed to be dependent on the type of the membranes and the degradation techniques. The experimental results are used in combination with the theoretical and numerical models to assess the fundamental understandings on the durability r
CHAPTER 1 INTRODUCTION 1 1.1 General 1 1.2 Motivation 4 1.3 Research Objectives 5 1.4 Organization of the dissertation 6 References 12 CHAPTER 2 EFFECT OF BIPOLAR PLATE MATERIALS ON THE STRESS DISTRIBUTION AND INTERFACIAL ELECTRICAL CONTACT RESISTANCE 14 2.1 Introduction 15 2.2 Stiffness and Electrical Contact Resistance 16 2.3 Numerical Simulation 19 2.4 Results and discussions 20 2.5 Conclusions 23 References 34 CHAPTER 3 INFLUENCE OF NANO-SCALE HETEROGENEITY IN CATALYST LAYER ON INTERFACIAL STRENGTH BETWEEN CATALYST LAYER AND MEMBRANE 37 3.1 Introduction 38 3.2 Experimental 42 3.3 Analytical 43 3.4 Finite Element Analyses 47 3.5 Results and Discussions 49 3.5.1 Physical Characterization 49 3.5.2 Mechanical Characterization 50 3.5.3 Numerical Analyses 54 FEA under non-graded condition 55 FEA under graded condition 57 3.6 Conclusions 61 References 78 CHAPTER 4 HETEROGENEITY IN CARBON FIBERS OF GAS-DIFFUSION LAYER AND DAMAGE EVOLUTION IN GAS-DIFFUSION ELECTRODE 81 4.1 Introduction 82 4.2 Analytical models 86 4.2.1 Asperity size independent contact resistance model. 86 4.2.2 Failure model for single carbon fiber 88 4.2.3 Flexural strength of GDL 91 4.2.4 Crack propagation in CL 93 4.2.5 Cohesive Zone model 97 4.3 Finite Element Analyses 103 4.3.1 Driving force for crack propagation in CL 103 4.3.2 Cohesive zone model 105 4.4 Results and discussions 107 4.4.1 Indentation results 107 4.4.2 Influence on Electrical Contact resistance 108 4.4.3 Fracture toughness of Teflon coated carbon fiber 109 4.4.4 Structural failure of GDL 110 4.4.5 Structural Integrity Principle of MEA 111 4.4.6 Driving force for crack propagation 114 4.4.7 Crack propagation in cell layers (Mechanical perspective) 117 4.5 Concluding remarks 119 References 138 CHAPTER 5 EFFECT OF GAS-DIFFUSION ELECTRODE MATERIAL HETEROGENEITY ON THE STRUCTURAL INTEGRITY OF POLYMER ELECTROLYTE FUEL CELL 143 5.1 Int
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College of Engineering(공과대학) > Mechanical Engineering(기계공학) > Theses(기계공학 석박사 학위논문)
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