Due to their peculiar low density properties, cellular solids are widely used in industries and play a very important role in our daily life. Two of the most studied celluar solids are honeycombs and foams. With the development of nanotechnology, another kind of cellular solids - carbon based materials are drawing more and more attentions nowadays, e.g., the carbon nanotube related researches. The other very hot research field is the bio-inspired materials. Many efforts have been made by the scientists all over the world and a lot of insightful results are obtained. No matter the well studied celluar solids or the newly studied natural and artificial materials, what we care about them are not only their mechicanl properties but also the multifunctionality they may display, in order that they could serve the human being more effectively and more conveniently. Therefore, in this thesis we have focused on the multifunctional hierarchical cellular solids. In the first chapter, by reviewing some recent developments of the cellular solids, honeycombs and carbon nanotube networks, we summarized the potential multifunctionality they show and thus the significance they may be of for practical applications. Based on this simple review, the motivation of this thesis is introduced, which is to explore the multifunctionalities of these two kinds of cellular solids more widely and deeply. In chapter 2, through the effective media model, the thermal and thermomechanical performances of the two-dimensional metal honeycombs (with relative density less than 0.3), hexagonal, triangular, square and Kagome honeycombs, are systematically studied. To improve the in-plane stiffness of the regular hexagonal honeycombs, in chapters 3 and 4 we proposed the multifunctional hierarchical honeycombs (MHH). The MHH is constructed by substituting the cell wall of an original regular honeycomb with five different equal mass lattices, hexagonal, triangular, Kagome, re-entrant hexagonal and chiral honeycombs, respectivley. Elastic and transport properties of the MHH with hexagonal, triangular and Kagome substructures are studied. In-plane stiffnesses of the MHH with re-entrant hexagonal and chiral honeycombs are analyzed. Chapter 5 involves the cellular solids, super carbon nanotubes (STs). To avoid the diameter shrinkage that the normal STs under uniaxial tension show, a new kind of hierarchical fibers with a negative Poisson’s ratio for tougher composites is proposed and their equivalent elastic parameters are calculated. Chapter 6 reported an application of the hierarchical fibers in bridged crack model. Chapter 7 provides conclusions and an outlook for the future work.

Multifunctional Hierarchical Cellular Solids / Sun, Yongtao. - STAMPA. - (2013). [10.6092/polito/porto/2507349]

Multifunctional Hierarchical Cellular Solids

SUN, YONGTAO
2013

Abstract

Due to their peculiar low density properties, cellular solids are widely used in industries and play a very important role in our daily life. Two of the most studied celluar solids are honeycombs and foams. With the development of nanotechnology, another kind of cellular solids - carbon based materials are drawing more and more attentions nowadays, e.g., the carbon nanotube related researches. The other very hot research field is the bio-inspired materials. Many efforts have been made by the scientists all over the world and a lot of insightful results are obtained. No matter the well studied celluar solids or the newly studied natural and artificial materials, what we care about them are not only their mechicanl properties but also the multifunctionality they may display, in order that they could serve the human being more effectively and more conveniently. Therefore, in this thesis we have focused on the multifunctional hierarchical cellular solids. In the first chapter, by reviewing some recent developments of the cellular solids, honeycombs and carbon nanotube networks, we summarized the potential multifunctionality they show and thus the significance they may be of for practical applications. Based on this simple review, the motivation of this thesis is introduced, which is to explore the multifunctionalities of these two kinds of cellular solids more widely and deeply. In chapter 2, through the effective media model, the thermal and thermomechanical performances of the two-dimensional metal honeycombs (with relative density less than 0.3), hexagonal, triangular, square and Kagome honeycombs, are systematically studied. To improve the in-plane stiffness of the regular hexagonal honeycombs, in chapters 3 and 4 we proposed the multifunctional hierarchical honeycombs (MHH). The MHH is constructed by substituting the cell wall of an original regular honeycomb with five different equal mass lattices, hexagonal, triangular, Kagome, re-entrant hexagonal and chiral honeycombs, respectivley. Elastic and transport properties of the MHH with hexagonal, triangular and Kagome substructures are studied. In-plane stiffnesses of the MHH with re-entrant hexagonal and chiral honeycombs are analyzed. Chapter 5 involves the cellular solids, super carbon nanotubes (STs). To avoid the diameter shrinkage that the normal STs under uniaxial tension show, a new kind of hierarchical fibers with a negative Poisson’s ratio for tougher composites is proposed and their equivalent elastic parameters are calculated. Chapter 6 reported an application of the hierarchical fibers in bridged crack model. Chapter 7 provides conclusions and an outlook for the future work.
2013
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2507349
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