Monday, 11 October 2004 - 2:40 PM

This presentation is part of : Torquato Symposium

Modeling and Design of Prismatic Cellular Materials

David L. McDowell, Ai-Jun Wang, and Rajesh Kumar. Georgia Institute of Technology, GWW School of Mechanical Engineering, Atlanta, GA 30332-0405

Various mechanical properties of metallic periodic prismatic cellular (honeycomb) structures with a number of different cell types are explored. A wide range of cell shapes, sizes and cell wall thicknesses can be fabricated using a metal oxide extrusion process developed at Georgia Tech. Effective elastic stiffness and initial yield strength of a range of metal honeycombs under in-plane compression and shear are reported as functions of relative density. Comparison among different honeycomb structures demonstrates that diamond cells, hexagonal periodic supercells composed of six equilateral triangles and the Kagome cells have superior in-plane mechanical properties among the set considered. Yield surfaces are constructed for various cell structures. Effects of missing or fractured cell walls on in-plane elastic stiffness and initial yield strength of metal honeycombs with square or triangular cells are investigated using finite element analysis. Results indicate that some properties sharply diminish with defect density, while others exhibit more gradual decay. Generalized continuum models are introduced to represent the cellular structure as an equivalent micropolar medium. The micropolar elastic constants for various cell structures are obtained by explicit analytical or numerical micromechanics solutions. The utility of the equivalent continuum model in analysis and design of these materials is explored. Finally, topology design methods for tailoring cell configurations of metal honeycombs to meet combined mechanical and thermal performance objectives are introduced and applied to heat sink design. Future potential applications are discussed, including extended micropolar theories that admit variation of cell wall thickness and shape/joint connectivity.

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