Sweet inspiration

A Bristol University-led EU project has developed a material that could provide industry with an alternative to currently available core materials used for building sandwich structures.

Project CHISMACOMB’s (CHIral SMArt honeyCOMB) material can be embedded with sensors and electromagnetic actuators to provide information about the structural integrity of sandwich structures used in civil, naval, aerospace, construction and electromagnetic shield applications.

The optimised chiral cellular core configuration of the auxetic, honeycomb-structured material also becomes thicker when stretched, providing greater flexibility without compromising strength.

The explanation behind the material’s unusual behaviour is a scientific principle called Negative Poisson’s ratio, which can occur in the cellular assemblies of honeycomb composite structures. In honeycombs, the ratio behaviour implies a stiffening geometric effect, which leads to high resistance, stiffness and strength. The auxetic behaviour also leads to the material’s bowl-shaped curve, which the researchers say is useful when manufacturing curved sandwich shells.

Fabrizio Scarpa, of the aerospace engineering department at Bristol, is the leader of the project. He said scientists have talked about the possibility of using a material with a Negative Poisson’s ratio since the 1920s.