Auxetic Blast Curtain demonstration

Auxetic blast curtains in action

Auxetic Chiral Honeycomb

Auxetic chiral honeycomb with embedded damage sensor

Auxetic materials

The world leading research into negative Poisson’s ratio (Auxetic) materials and structures occurring at the University of Exeter Multi-Functional Materials group examines the counter-intuitive property where a material expands laterally when stretched axially, i.e. it gets fatter when it is stretched!

This surprising property is widely occurring in the natural world and has even been measured in the human body with skin, artery walls and trabechular bone all possessing a negative Poisson’s ratio.

Auxetic materials possess a number of benefits over conventional materials:

  • When put into flexure they form a dome shape rather than the conventional saddle shape which is ideal for the production of doubly curved components such as aircraft and automobile components.
  • When indented the material under the indenter densifies acting to make the material harder, ideal for indentation resistant foam packaging
  • Poisson’s ratio balancing, allowing the use of dissimilar materials where auxetic content is used to match the lateral expansions of components to prevent internal stresses under loading.
  • Auxetic materials have been successfully used to enhance the vibration damping of cellular structures used in sandwich panel cores for use in aerospace structures.

The majority of negative Poisson’s ratio materials are cellular solids such as honeycombs and foams, however work into fibres and recently composites (including carbon fibre composites) has allowed the production of auxetic fibre composites which may be used in conjunction with auxetic honeycombs or foams to create entirely auxetic sandwich structures and to make auxetic fabrics used to develop next generation blast curtains.