Analysis of PEM fuel cell experimental data using Principal Component Analysis and Multi linear regression

International audiencePolarisation curves performed at the Fuel Cell System Laboratory (FC LAB) at Belfort on a PEM fuel cell stack using a homemade fully instrumented test bench led to more than 100 variables depending on time. Visualising and analysing all the different test variables are complex. In this work, we show how the Principal Component Analysis (PCA) method helps to explore correlations between variables and similarities between measurements at a specific sampling time (individuals). To complete this method, an empirical model of the PEM fuel cell is proposed by linking the different input parameters to the cell voltage using Multiple Linear Regressions. Proton exchange membrane (PEM) fuel cell; Principal Component Analysis (PCA); Multiple Linear Regression; statistical analysis

Peelback of highly oriented cellulosic fibres

International audienceAn original study of peelback of cellulosic fibres spun using the N-methylmorpholine N-oxide (NMMO) process was performed. 13 micrometre diameter fibres were peeled under a microscope. Due to the high orientation of the material, the rupture could propagate in the centre of the fibres. Fibres presenting very different Fibrillability Index (FI=0 or FI=5) and hydration (swollen in water or freezedried) were studied. The resulting surfaces were analysed using Scanning Electron Microscopy (SEM). They showed the original formation of regularly spaced ribs corresponding to tearing of a homogeneous oriented material for the non fibrillable fibres. The structure of fibrillable fibres appeared through the creation of fibrils. Measurements of the energy release rate were performed with a set of each kind of fibres. Low values of this energy were obtained, corresponding to the formation of small ribs, due to the high orientation of the cellulose molecules. The energy values can be increased by the occurence of fibrils in the case of fibrillable fibres

Compression hétérogène de Couche de Diffusion de Gaz dans la Pile à Combustible de type PEMFC

International audienceIn a Proton Exchange Membrane Fuel Cell assembly, the Gas Diffusion Layers are submitted tocompression between the fluidic gas circuits. Thus, this highly porous carbon fibre material undergoesheterogeneous finite strains that influence the fuel cell performances and durability. In this work, theeffect of pattern size on the material deformation was investigated experimentally, and compared withFinite Element Modeling computed using homogeneous mechanical behavior from the state of the art.Dans l'assemblage des piles à combustible à membrane échangeuse de protons, la couche de diffusion de gaz est soumise à une compression par des motifs. Ce matériau très poreux composé de fibres de carbones subit donc de grandes déformations hétérogènes, qui influencent les performances et la durabilité des piles. Une étude expérimentale de l'effet de la taille des motifs sur la réponse du matériau est présentée ici, ainsi que la simulation numérique de ce cas de charge avec les modèles de matériau homogènes classiquement utilisés dans la littérature

Compression hétérogène de Couche de Diffusion de Gaz dans la Pile à Combustible de type PEMFC

International audienceIn a Proton Exchange Membrane Fuel Cell assembly, the Gas Diffusion Layers are submitted tocompression between the fluidic gas circuits. Thus, this highly porous carbon fibre material undergoesheterogeneous finite strains that influence the fuel cell performances and durability. In this work, theeffect of pattern size on the material deformation was investigated experimentally, and compared withFinite Element Modeling computed using homogeneous mechanical behavior from the state of the art.Dans l'assemblage des piles à combustible à membrane échangeuse de protons, la couche de diffusion de gaz est soumise à une compression par des motifs. Ce matériau très poreux composé de fibres de carbones subit donc de grandes déformations hétérogènes, qui influencent les performances et la durabilité des piles. Une étude expérimentale de l'effet de la taille des motifs sur la réponse du matériau est présentée ici, ainsi que la simulation numérique de ce cas de charge avec les modèles de matériau homogènes classiquement utilisés dans la littérature

Rheological behavior of cellulose/monohydrate of n-methylmorpholine n-oxide solutions. Part 1: Liquid state

International audienceSteady-state and dynamic experiments have been performed on solutions containing cellulose dissolved in monohydrate of N-methylmorpholine N-oxide (NMMO). The dependence of the zero-shear viscosity η0, and of the terminal relaxation time τc, on concentration, average degree of polymerization (DP̄) and temperature are discussed. The behavior of this semi-rigid, polymolecular polymer in solution differs from that of flexible monodisperse ones. The slope of the plot of log (η0) versus, on the one hand, log (c) at fixed molecular weight (DP̄) = 600, and, on the other hand, log (DP̄) at fixed concentration (c = 5% w/w) are equal to 4.6 and 5 respectively, instead of 3.4 in the concentrated region. Experimental data for the shear modulus were fitted using the classical Doi-Edwards equation with a log normal distribution of relaxation time. This distribution is compared to the distribution of DP

Compression hétérogène de Couche de Diffusion de Gaz dans la Pile à Combustible de type PEMFC

International audienceIn a Proton Exchange Membrane Fuel Cell assembly, the Gas Diffusion Layers are submitted tocompression between the fluidic gas circuits. Thus, this highly porous carbon fibre material undergoesheterogeneous finite strains that influence the fuel cell performances and durability. In this work, theeffect of pattern size on the material deformation was investigated experimentally, and compared withFinite Element Modeling computed using homogeneous mechanical behavior from the state of the art.Dans l'assemblage des piles à combustible à membrane échangeuse de protons, la couche de diffusion de gaz est soumise à une compression par des motifs. Ce matériau très poreux composé de fibres de carbones subit donc de grandes déformations hétérogènes, qui influencent les performances et la durabilité des piles. Une étude expérimentale de l'effet de la taille des motifs sur la réponse du matériau est présentée ici, ainsi que la simulation numérique de ce cas de charge avec les modèles de matériau homogènes classiquement utilisés dans la littérature

Mechanical response of carbon paper Gas Diffusion Layer under patterned compression

International audienceThe Proton Exchange Membrane Fuel Cell (PEMFC) performances are strongly impacted by the compression of the Gas Diffusion Layer (GDL). Despite its fibrous microstructure, this material is usually considered as a continuous medium and characterized with uniform loading. However, the GDL is subjected to a heterogeneous compression onto rib/channel patterns in the fuel cell assembly. In the present study, an original behavior of the GDL response is experimentally revealed when the material is loaded with a rib/channel pattern, compared to uniform compression. The tests are simulated by finite element modeling using a classical strain-dependent elastic law, using parameters fitted from uniform compression experiments. It is shown that the numerical results do not reproduce the effect of pattern observed experimentally. Hypotheses to interpret these results involve mechanisms at the fiber microscale including fiber fracture, cross-link breakage and fiber rearrangement, which are exacerbated by larger material deformation caused by the heterogeneous loading

Determination of the static and kinetic friction coefficients between the catalyst layer and the microporous layer - influence of the MEA components and its assembly conditions

International audienceMembrane electrode assemblies (MEA) are composed of five principal layers: two gas diffusion layers on top of two catalyst layers surrounding the membrane. The understanding of the mechanical behavior at the different interfaces of the MEA is therefore essential and will be the subject of this study through the development of a new methodology to evaluate the friction coefficients between the different layers. The analysis of the MEA components and their assembly process impact will be considered. A morphological analysis based on confocal microscopy observations of the catalyst layer/microporous layer interface was conducted to evaluate the roughness of the different surfaces submitted to friction. Results show that the static friction increases with the addition of microporous layers and catalyst layers on their substates. The friction coefficients also increase after a low pressure hot pressing but they surprisingly decrease after an assembly performed at a high pressure

Benchmarking carbon-supported Pt-based oxygen reduction reaction electrocatalysts for PEMFC cathodes

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