The tensile ductility of cellular Solids: The role of imperfections

Authors
Ronan, W 
Deshpande, VS 
Fleck, NA 

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Type
Article
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Abstract

© 2016 Metallic and polymeric foams typically possess a low tensile failure strain of a few percent despite the fact that the parent solid can have high ductility (10% or more). This is remarkable as foams are bending-dominated in their structural response, and it is widely accepted that beams have a high ductility in bending compared to a bar in uniaxial tension. Possible reasons for this paradox are explored for a 2D hexagonal honeycomb, and for a so-called ‘lotus cellular material’, made from an elastic-plastic parent solid. Finite element simulations reveal that there is only a small drop in tensile ductility due to the presence of Plateau borders or due to the random misalignment of nodes; a much greater drop in ductility results from missing cell walls (equivalent to misshapen cells) or to the presence of stiff inclusions. The drop in ductility due to inclusions is associated with the multi-axial stress state that exists in their vicinity. This study emphasises the need for a uniform microstructure in order for foams to possess a high macroscopic ductility.

Publication Date
2016-12-15
Online Publication Date
2016-10-11
Acceptance Date
2016-10-10
Keywords
Cellular foams, Elastic plastic solids, Finite element, Foam structures, Micro-mechanics, Stress strain, Tension
Journal Title
International Journal of Solids and Structures
Journal ISSN
0020-7683
1879-2146
Volume Title
102-103
Publisher
Elsevier BV