3D characterization, modeling, and effective thermal conductivity of open aluminum foams

Foams made of aluminum or aluminum alloys are used in many application areas, e.g. as heat exchangers, catalysts or in light weight construction. Physical properties of a foam such as thermal conductivity or elasticity are heavily influenced by its microstructure. Therefore, an understanding of the change of these properties through the microstructure is crucial for the choice of optimal foams for given applications. The use of foam models is a powerful tool for studying these relations. Systems of edges or facets of random tessellations are often used as models for open or closed foams, respectively. The models are fitted to the microstructure of the foam cells using geometric characteristics which are estimated from tomographic images. Changing the model parameters, foams with a slightly modified microstructure can be generated. Numerical simulations in these model foams allow for an investigation of relations between the geometric structure of a material and its physical properties. Using this approach an optimization of foams for particular applications and a virtual design of new materials is possible. In this paper, the cell structure of an open aluminum foam is analyzed using a tomographic image of the material. Based on the estimated characteristics a Laguerre tessellation model, i.e. a weighted Voronoi tessellation, is fitted to the foam structure. Starting from the edge system of this tessellation, the varying local thickness of the struts is reproduced using locally adaptable morphology. Finally, heat transfer is simulated in both the original image and images of various model structures and the results are compared.