Extraction of Curved Fibers from 3D Data

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)3882 LNCS659-67

3D microstructure modeling of compressed fiber-based materials

A novel parametrized model that describes the 3D microstructure of compressed fiber-based materials is introduced. It allows to virtually generate the microstructure of realistically compressed gas-diffusion layers (GDL). Given the input of a 3D microstructure of some fiber-based material, the model compresses the system of fibers in a uniaxial direction for arbitrary compression rates. The basic idea is to translate the fibers in the direction of compression according to a vector field which depends on the rate of compression and on the locations of fibers within the material. In order to apply the model to experimental 3D image data of fiber-based materials given for several compression states, an optimal vector field is estimated by simulated annealing. The model is applied to 3D image data of non-woven GDL in PEMFC gained by synchrotron tomography for different compression rates. The compression model is validated by comparing structural characteristics computed for experimentally compressed and virtually compressed microstructures, where two kinds of compression – using a flat stamp and a stamp with a flow-field profile – are applied. For both stamps types, a good agreement is found. Furthermore, the compression model is combined with a stochastic 3D microstructure model for uncompressed fiber-based materials. This allows to efficiently generate compressed fiber-based microstructures in arbitrary volumes

Stochastic 3D Modeling of Fiber Based Materials

A stochastic multi-layer model is developed describing the microstructure of materials which are built up of strongly curved, but almost horizontally oriented fibers. This fully parametrized model is based on ideas from stochastic geometry and multivariate time series analysis. It consists of independent layers which are stacked together, where each single layer is described by a 2D germ-grain model dilated in 3D. The germs form a Poisson point process and the grains are given by random polygonal tracks describing single fibers in terms of multivariate time series. Exemplarily, on the basis of 2D data from SEM images, the parameters of the multi-layer model are fitted to the microstructure of a non-woven material which is used for gas-diffusion layers in PEM fuel cells. Therefore, an algorithm is presented which automatically extracts typical fiber courses from SEM images. Finally, the multi-layer model is validated by comparing structural characteristics computed for 3D data gained by synchrotron tomography from the same material, and for realizations drawn from the multi-layer model. (C) 2012 Elsevier B.V. All rights reserved

Stochastic Aspects of Mass Transport in Gas Diffusion Layers

The relationship between the 3D morphology of gas-diffusion layers (GDL) of HT-PEFCs and their functionality is analyzed. A stochastic model describing the microstructure of paper-type GDL is combined with the Lattice-Boltzmann method (LBM) to simulate gas transport within the GDL microstructure. Virtual 3D microstructures representing paper-type GDL are generated by a stochastic model, where the binder morphology is systematically modified. On these structures single phase, single component gas flow is computed by the LBM. Quality criteria evaluating the spatial homogeneity of gas supply are introduced and related to the binder morphology. The spatial homogeneity of the gas supply is analyzed by a parametrized stochastic model describing the gas flow at the exit of the GDL. This approach gives insight into the spatial structure of the gas flow at the GDL exit. The quality of gas supply is quantified by characterizing size and arrangement of regions with high gas supply. This stochastic gas flow model predicts the quality of gas supply for further binder morphologies. Analyzing the quality criteria and the stochastic evaluation of the spatial structure of the gas flow field at the GDL exit, it is found that the binder morphology has an essential influence on the gas supply