Auxetic behavior from rotating triangles

The auxetic behavior of materials with a negative Poisson's ratio is discussed. This property gives a material several beneficial effects such as increased shear stiffness, increased plane strain fracture toughness, increased indentation resistance and improved acoustic damping properties. The Poisson's ratio is not constant and varies with strain and the initial geometry parameters. The deformations of the triangles inevitably occur in parallel with the rotations, which reduce the extent of the auxetic effect and allows the system to shear. The force-field based simulations suggest that auxetic behavior is retained, which illustrates that the rotating triangles mechanism can be a very effective way for introducing negative Poisson's ratios in real materials.