scholarly journals Investigation on Mechanical Properties of a Carbon Paper Gas Diffusion Layer through a 3-D Nonlinear and Orthotropic Constitutive Model

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6341
Author(s):  
Yanqin Chen ◽  
Yuchao Ke ◽  
Yingsong Xia ◽  
Chongdu Cho
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Mechanical Performance ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Operation Conditions ◽  
Significant Difference ◽  
Assembly Technology ◽  
Simulation Results

The mechanical loads that gas diffusion layers (GDLs) withstand in polymer electrolyte membrane fuel cell (PEMFC) stacks are sensitive to the assembly and working conditions. The mechanical properties of GDLs mostly depend on their composition materials, microstructural characteristics, operation conditions, etc. An accurate and comprehensive understanding of the mechanical performance of GDLs is significant for predicting the stress distribution and improving the assembly technology of PEMFC stacks. This study presented a novel 3-D nonlinear and orthotropic constitutive model of a carbon paper GDL to represent the material stiffness matrix with its compressive, tensile, and shear properties. Numerical simulations were performed based on the 3-D constitutive model, and the proposed 3-D model was validated against the experimental data reported previously. It is found that the simulation results of the 3-D constitutive model show a good agreement with the experimental results. Besides, the novel 3-D nonlinear and orthotropic model was applied in the overall stress simulation of a simplified PEMFC unit cell, compared to a conventional 3-D linear and isotropic model, and the simulation results of the two models show a significant difference.

Mechanical behavior simulation: NCF/epoxy composite processed by RTM

2018 ◽  
Vol 27 (2) ◽  
pp. 66-75 ◽  
Author(s):  
Francisco Maciel Monticeli ◽  
David Daou ◽  
Mirko Dinulović ◽  
Herman Jacobus Cornelis Voorwald ◽  
Maria Odila Hilário Cioffi
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
Mechanical Behavior ◽  
Epoxy Resin ◽  
Defect Formation ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Final Conclusion ◽  
Simulation Results ◽  
Matrix Reinforcement

Considering aeronautics requirements, academies and industries are developing matrixes and reinforcements with higher mechanical performance. The same occurs with the process where new studies focus on obtaining composites with suitable matrix/reinforcement interface. The use of epoxy resin and carbon fiber with high mechanical performance does not guarantee a composite with high mechanical properties, considering imperfections and void formation along the laminate in case of inappropriate processing parameters. The aim of this article was to analyze and quantify the mechanical behavior of polymer composite reinforced with continuous fibers using finite element methodology and postprocessing software simulation. In addition, the classical laminate theory and finite elements were used to simulate flexural and tensile tests of composite specimens. Simulation results were compared with experimental test results using a carbon fiber noncrimp fabric quadriaxial/epoxy resin composite processed by resin transfer molding. Although void volume fraction for structural materials presenting results under aeronautics requirements regarding of 2%, imperfections like lack of resin and impregnation discontinuity showed an influence in tensile and flexural experimental results. Experimental mechanical behavior decreased 10% of strength, in comparison with simulation results due to imperfection on impregnation measured by C-Scan map. Improvement in processing procedures could able to provide greater impregnation continuity, reducing defect formation and ensuring better matrix/reinforcement interface. As a final conclusion, the process plays a role as important as the characteristics of reinforcement and matrix and, consequently, the mechanical properties.

The Impact of an MPL on Water Management of an Operating PEMFC Using Synchrotron X-Ray Radiography

2012 ◽  
Author(s):  
J. Lee ◽  
J. Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Water Management ◽  
Current Density ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Stoichiometric Ratio ◽  
Operation Performance ◽  
X Ray ◽  
Electrolyte Membrane ◽  
The Impact

High quality through-plane images of an operating polymer electrolyte membrane fuel cell (PEMFC) were visualized by employing synchrotron X-ray radiography to quantify liquid water in gas diffusion layers (GDL). Two types of GDLs, Toray carbon paper with and without micro-porous layers (MPLs), were employed and imaged during the operation. Performance data and x-ray images of these GDLs are compared to determine the impact of an MPL on water management. At low current density (<0.4A/cm2) under high stoichiometric ratio, the MPL has little overall effect, but may behave as a diffusion barrier for reactants. At higher current density (0.6A/cm2) and under low stoichiometric ratios, the MPL is observed to significantly affect the water management of the PEMFC and is credited for increased cell performance.

scholarly journals Numerical Theoretical Study on Mechanical Properties of New Reinforced Tenon Precast Shear Walls

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Wei Chen ◽  
Qing Wu ◽  
Dongyue Wu ◽  
Longji Dang ◽  
Feifei Jiang
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Equivalent Plastic Strain ◽  
Shear Wall ◽  
Joint Interface ◽  
Distribution Diagram ◽  
Precast Shear Wall ◽  
Bending Capacity ◽  
Assembly Technology ◽  
Simulation Results

Precast construction technologies have several advantages in industrialized production, such as quality control and energy conservation. However, the joint interface slippage between the precast components causes detrimental effect on the mechanical properties, such as dowel shear stress on the connecting steel bars, which strictly restricts the development of assembly technology in aseismic structure. In order to eliminate the horizontal slippage along the assemble joint and optimize the mechanical performance of horizontal joint connections, a new reinforced tenon joint precast shear wall is proposed in this paper. Finite element numerical simulations are conducted on three reinforced tenon joint specimens and a reference specimen to understand the mechanical properties of the reinforced tenon and boundary confinement components of shear wall. The load-displacement curves, the equivalent plastic strain distribution diagram, and the concrete damage distribution diagram are obtained. It is found that the boundary components provide bending strength and the reinforced tenon can reduce the harmful influence of dowel-action shear stress on longitudinal connecting reinforcements. Therefore, the bending and shearing forces are separated at the joint interface. Based on the numerical simulation results and the calculation theory of normal section bearing capacity, the theoretical calculation bending capacity formula of reinforced tenon precast shear wall is established. The obtained calculation results are in good agreement with the simulation results and can accurately reflect the bending capacity of the jointed interface.

Graduated Flow Resistance Through a GDL in a Novel PEM Stack

2009 ◽  
Author(s):  
Terry B. Caston ◽  
Kanthi L. Bhamidipati ◽  
Haley Carney ◽  
Tequila A. L. Harris
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte Membrane ◽  
Catalyst Layer ◽  
Current Density Distribution ◽  
Pem Fuel Cell ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Electrolyte Membrane

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability, and therefore a graduated resistance to flow throughout the GDL. It has been shown that using conventional materials the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack, where the reactant gases are supplied through the side of the GDL rather than through flow field channels, which are machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, and thickness of the GDL on the expected current density distribution at the catalyst layer are studied. Three different thicknesses are investigated, and it is found that as GDL thickness increases, more uniform reactant distribution over the face of the GDL is obtained. Results also show that it is necessary to design a GDL with a much higher in-plane resistance than through-plane resistance for the unconventional PEM stack studied.

Improvement of Electrical and Thermal Properties of Epoxy Based Graphite Bipolar Plate for PEMFC

2007 ◽  
Vol 26-28 ◽  
pp. 853-856 ◽  
Author(s):  
Hong Ki Lee ◽  
Soo Heun Chae ◽  
Joong Pyo Shim ◽  
Sung Won Yang
Keyword(s):  
Thermal Properties ◽  
Polymer Electrolyte Membrane ◽  
Expanded Graphite ◽  
Graphite Powder ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Mechanical And Thermal Properties ◽  
Carbon Cloth ◽  
Graphite Composite

The decrease of material cost for manufacturing fuel cell stack is strongly required for overcoming commercial restriction. The epoxy based graphite bipolar plate (BP) for polymer electrolyte membrane fuel cells (PEMFC) has been prepared and electrical, mechanical and thermal properties were compared. The density of graphite composite bipolar plate showed from 1.67 to 2.54 as graphite content is increased from 60 to 80w/o and decreased as expanded graphite was added. The contact resistance between epoxy/graphite bipolar plate and gas diffusion layer (GDL) had lower value using carbon cloth than carbon paper for GDL. The conformation of thermal stability, improvement of mechanical and electrical properties was accomplished by addition of expanded graphite powder.

Direct Spraying of Catalyst Inks for PEMFC Electrode Manufacturing

2011 ◽  
Author(s):  
Casey J. Hoffman ◽  
Daniel F. Walczyk
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Gas Diffusion ◽  
Production Costs ◽  
Nano Particles ◽  
Process Efficiency ◽  
Carbon Paper ◽  
Membrane Electrode ◽  
Electrolyte Membrane

Automated manufacturing techniques are needed to reduce production costs for polymer electrolyte membrane (PEM) fuel cell electrodes. The work presented in this paper focuses on the use of a low pressure, low volume direct spray valve that uses air pressure to atomize fluids and transfer them to a gas diffusion layer (GDL) to produce a gas diffusion electrode (GDE). Two of these electrodes would then be joined with a polymer electrolyte membrane to produce a fuel cell membrane electrode assembly (MEA). Accurate and reproducible deposition methods such as this will result in less wasted materials, especially platinum, and increased throughput compared to common laboratory-scale techniques such as paint brushing and Mayer-rod coating. In this study, the production of inks will be discussed including a catalyst ink containing platinum nano-particles supported on carbon (20% loading by weight) and a similar analog ink which is identical except for that it does not contain the platinum. Two different substrates, mylar transparency film and actual carbon paper GDL substrate will be used and presented in this study. Ink rheology (viscosity, solids content, etc.) will also be discussed as it pertains to optimizing spray pattern uniformity and process efficiency. Initial results of thickness measurements which are used for determining uniformity and the required overlapping of multiple coats will be presented. In addition, a comparison of scanning electron microscopy (SEM) images of electrode surface structures prepared by mayer-rod and spraying will be shown. A brief discussion of the future work planned by the authors in order to study the effects of processing variables on actual fuel cell performance will also be given.

Weldability - Behavior of Welded Reinforcement

2019 ◽  
Vol 70 (10) ◽  
pp. 3469-3472
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Current Work ◽  
Carbon Equivalent ◽  
Work Process ◽  
Ultimate Limit

Weldability involves two aspects: welding behavior of components and safety in operation. The two aspects will be reduced to the mechanical characteristics of the elements and to the chemical composition. In the case of steel reinforcing rebar’s, it is reduces to the percentage of Cech(carbon equivalent) and to the mechanical characteristics: the yielding limit, the ultimate limit, and the elongations which after that represent the ductility class in which the re-bars is framed. The paper will present some types of steel reinforcing rebar’s with its mechanical characteristics and the welding behavior of those elements. In the current work, process-related behavior of welded reinforcement, joint local and global mechanical properties, and their correlation with behavior of normal reinforcement and also the mechanical performance resulted in this type of joints. Keywords: welding behavior, ultimate limit, reinforcing rebar’s

scholarly journals Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Mechanical Performance ◽  
Tensile Elongation ◽  
Sisal Fiber ◽  
Fiber Reinforced ◽  
Impact Performance ◽  
The Matrix ◽  
Blending Process ◽  
Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

scholarly journals Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2091
Author(s):  
Daniela Mileva ◽  
Jingbo Wang ◽  
René Androsch ◽  
Katalee Jariyavidyanont ◽  
Markus Gahleitner ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Metallocene Catalyst ◽  
Nucleating Agent ◽  
Random Copolymers ◽  
Rapid Cooling ◽  
Significant Difference ◽  
Chip Calorimetry ◽  
High Cooling Rates ◽  
Fast Scanning Chip Calorimetry

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

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