Negative Poisson's ratios in metal nanoplates.
The Poisson's ratio is a fundamental measure of the elastic-deformation behaviour of materials. Although negative Poisson's ratios are theoretically possible, they were believed to be rare in nature. In particular, while some studies have focused on finding or producing materials with a negative Poisson's ratio in bulk form, there has been no such study for nanoscale materials. Here we provide numerical and theoretical evidence that negative Poisson's ratios are found in several nanoscale metal plates under finite strains. Furthermore, under the same conditions of crystal orientation and loading direction, materials with a positive Poisson's ratio in bulk form can display a negative Poisson's ratio when the material's thickness approaches the nanometer scale. We show that this behaviour originates from a unique surface effect that induces a finite compressive stress inside the nanoplates, and from a phase transformation that causes the Poisson's ratio to depend strongly on the amount of stretch.
1] School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea [2] Multiscale and Multiphysics Simulations Group and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea.
Duc Tam
DT
Ho
1] School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea [2] Multiscale and Multiphysics Simulations Group and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea.
Soon-Dong
SD
Park
1] School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea [2] School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea.
Soon-Yong
SY
Kwon
School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea.
Kibog
K
Park
1] School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea [2] Multiscale and Multiphysics Simulations Group and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology, Ulsan 689-798, South Korea.
Sung Youb
SY
Kim