Auxetic materials

Abstract The current status of research into auxetic (negative Poisson's ratio) materials is reviewed, with particular focus on those aspects of relevance to aerospace engineering. Developments in the modelling, design, manufacturing, testing, and potential applications of auxetic cellular solids, polymers, composites, and sensor/actuator devices are presented. Auxetic cellular solids in the forms of honeycombs and foams are reviewed in terms of their potential in a diverse range of applications, including as core materials in curved sandwich panel composite components, radome applications, directional pass band filters, adaptive and deployable structures, MEMS devices, filters and sieves, seat cushion material, energy absorption components, viscoelastic damping materials, and fastening devices. The review of auxetic polymers includes the fabrication and characterization of microporous polymer solid rods, fibres, and films, as well as progress towards the first synthetic molecular-level auxetic polymer. Potential auxetic polymer applications include self-locking reinforcing fibres in composites, controlled release media, and self-healing films. Auxetic composite laminates and composites containing auxetic constituents are reviewed and enhancements in fracture toughness, and static and low velocity impact performance are presented to demonstrate potential in energy absorber components. Finally, the potential of auxetics as strain amplifiers, piezoelectric devices, and structural health monitoring components is presented.