Computer Aided Engineering of new materials
Computer Tomography (CT) images in combination with current computer hardware and new algorithms typify the recent advances in computerized material design. The properties can be computed directly on the images. At the same time, the images are useful for developing geometric material models. These parameterized models can produce virtual CT images, from which the properties of new materials can be predicted using property computations. Once model parameters with improved properties are determined, the manufacture of the new, superior material is worthwhile. And afterwards, CT is again the method of choice to verify that the real material geometry corresponds to the predicted (virtual) optimal one.
Several groups at Fraunhofer Institute for Industrial Mathematics (ITWM) use this approach in a number of projects, with either public or industrial funding. Some of these projects will be discussed here under the perspective of using CT-images. The main applications are the design of filter media, the design and property prediction of layers in Proton Exchange Membrane (PEM) fuel cells, and the simulation of paper dewatering felts. Interesting and computable are also pore size distributions, one-phase and two-phase flows, filter efficiency and filter life time, electrical and thermal conductivity and effective elastic properties.
To warrant the transferability of the results and the knowledge gained in these projects, all material models and material property computations are usable by ITWMs partners and customers through the GeoDict simulation software suite.
Modeling of materials based on CT-Images
CT provides the best impression of a material’s geometry, as long as the available resolution is just below 1 ?m and the contrast is appropriate. Fibrous materials, also called nonwoven, found in diverse application areas such as hygiene, filtration or carpeting, pose challenges to CT in both respects. Synthetic fibers often show little contrast, and increasingly smaller fibers are used, particularly in filtration applications. Fiber diameters that are significantly below 1 ?m require very high resolution CT. Nonwoven models are also suitable for fiber-reinforced composites where the fiber-free space is simply occupied by a matrix material instead of air. Besides fibers, models for various components of PEM fuel cells, ceramics, woven textiles and woven wire meshes, and felts are considered. Figure 1 shows a variety of materials, partly as real CT and partly as virtual CT.