title: Hierarchical honeycomb auxetic metamaterials.
abstract: Most conventional materials expand in transverse directions when they are compressed uniaxially resulting in the familiar positive Poisson's ratio. Here we develop a new class of two dimensional (2D) metamaterials with negative Poisson's ratio that contract in transverse directions under uniaxial compressive loads leading to auxeticity. This is achieved through mechanical instabilities (i.e., buckling) introduced by structural hierarchy and retained over a wide range of applied compression. This unusual behavior is demonstrated experimentally and analyzed computationally. The work provides new insights into the role of structural organization and hierarchy in designing 2D auxetic metamaterials, and new opportunities for developing energy absorbing materials, tunable membrane filters, and acoustic dampeners.
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Davood
authors.initials: D
authors.lastname: Mousanezhad
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Sahab
authors.initials: S
authors.lastname: Babaee
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Hamid
authors.initials: H
authors.lastname: Ebrahimi
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Ranajay
authors.initials: R
authors.lastname: Ghosh
authors.affiliation: Mechanical and Industrial Engineering Department, Qatar University, Doha, Qatar.
authors.forename: Abdelmagid Salem
authors.initials: AS
authors.lastname: Hamouda
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Katia
authors.initials: K
authors.lastname: Bertoldi
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Ashkan
authors.initials: A
authors.lastname: Vaziri