title: Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials.
abstract: We describe a new class of negative Poisson's ratio (NPR) open cell PU-PE foams produced by blocking the shape memory effect in the polymer. Contrary to classical NPR open cell thermoset and thermoplastic foams that return to their auxetic phase after reheating (and therefore limit their use in technological applications), this new class of cellular solids has a permanent negative Poisson's ratio behavior, generated through multiple shape memory (mSM) treatments that lead to a fixity of the topology of the cell foam. The mSM-NPR foams have Poisson's ratio values similar to the auxetic foams prior their return to the conventional phase, but compressive stress-strain curves similar to the ones of conventional foams. The results show that by manipulating the shape memory effect in polymer microstructures it is possible to obtain new classes of materials with unusual deformation mechanisms.
authors.affiliation: Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Boba
authors.affiliation: Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bianchi
authors.affiliation: Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
authors.forename: Greg
authors.initials: G
authors.lastname: McCombe
authors.affiliation: Metamaterials Unit, University of Malta , Msida MSD 2080, Malta.
authors.forename: Ruben
authors.initials: R
authors.lastname: Gatt
authors.affiliation: Materials Science and Engineering, Georgia Institute of Technology , 801 Ferst Drive North West, Atlanta, Georgia 30332-029, United States.
authors.forename: Anselm C
authors.initials: AC
authors.lastname: Griffin
authors.affiliation: H H Wills Physics Laboratory, University of Bristol , Tyndall Avenue, Bristol, BS8 1TS, United Kingdom.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Richardson
authors.affiliation: Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Scarpa
authors.affiliation: Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Hamerton
authors.affiliation: Metamaterials Unit, University of Malta , Msida MSD 2080, Malta.
authors.forename: Joseph N
authors.initials: JN
authors.lastname: Grima
keywords: foam; metamaterial; negative Poisson’s ratio; polyurethane; shape memory