An Anisotropic Auxetic 2D Metamaterial Based on Sliding Microstructural Mechanism.

A new 2D microstructure is proposed herein in the form of rigid unit cells, each taking the form of a cross with two opposing crossbars forming slots and the other two opposing crossbars forming sliders. The unit cells in the microstructure are arranged in a rectangular array in which the nearest four neighboring cells are rotated by 90° such that a slider in each unit cell is connected to a slot from its nearest neighbor. Using a kinematics approach, the Poisson's ratio along the axes of symmetry can be obtained, while the off-axis Poisson's ratio is obtained using Mohr's circle. In the special case of a square array, the results show that the Poisson's ratio varies between 0 (for loading parallel to the axes) and -1 (for loading at 45° from the axes). For a rectangular array, the Poisson's ratio varies from 0 (for loading along the axes) to a value more negative than -1. The obtained results suggest the proposed microstructure is useful for designing materials that permit rapid change in Poisson's ratio for angular change.