What are auxetic materials?

Auxetic materials are materials with a negative Poisson’s Ratio, i.e. become fatter when stretched and thinner when squashed .

Figure 1: Loading in the Y-direction of a conventional and auxetic honeycomb structure
 
 

What are auxetic materials like?

Very few exist naturally but recently more have been fabricated by modifying the microstructure of existing materials e.g. foams, polymers. Structures for molecular auxetics have been proposed, which are expected to be intrinsically superior to the microstructural auxetics so far developed .

What advantages do auxetic materials offer?

Apart from the scientific value of having materials with a negative Poisson`s ration, auxetic materials show enhanced mechanical properties such as:

• increased shear stiffness
• increased plane strain fracture toughness
• increased indentation resistance

which make them superior to classical materials for many practical applications.