Materials 2013, 6(2), 699-712; doi:10.3390/ma6020699

Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites

1 Laboratory of Bio-Inspired Nanomechanics "Giuseppe Maria Pugno", Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy 2 Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, Trento I-38123, Italy
* Author to whom correspondence should be addressed.
Received: 27 November 2012; in revised form: 9 January 2013 / Accepted: 15 January 2013 / Published: 22 February 2013
(This article belongs to the Special Issue Advances in Bio-inspired Materials)
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Abstract: In this paper, a new kind of hierarchical tube with a negative Poisson’s ratio (NPR) is proposed. The first level tube is constructed by rolling up an auxetic hexagonal honeycomb. Then, the second level tube is produced by substituting the arm of the auxetic sheet with the first level tube and rolling it up. The Nth ( ) level tube can be built recursively. Based on the Euler beam theory, the equivalent elastic parameters of the NPR hierarchical tubes under small deformations are derived. Under longitudinal axial tension, instead of shrinking, all levels of the NPR hierarchical tubes expand in the transverse direction. Using these kinds of auxetic tubes as reinforced fibers in composite materials would result in a higher resistance to fiber pullout. Thus, this paper provides a new strategy for the design of fiber reinforced hierarchical bio-inspired composites with a superior pull-out mechanism, strength and toughness. An application with super carbon nanotubes concludes the paper.
Keywords: negative Poisson’s ratio (NPR); hierarchy; super carbon nanotubes (STs); auxetic; pull-out; toughness

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MDPI and ACS Style

Sun, Y.; Pugno, N. Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites. Materials 2013, 6, 699-712.

AMA Style

Sun Y, Pugno N. Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites. Materials. 2013; 6(2):699-712.

Chicago/Turabian Style

Sun, Yongtao; Pugno, Nicola. 2013. "Hierarchical Fibers with a Negative Poisson’s Ratio for Tougher Composites." Materials 6, no. 2: 699-712.

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