Designing Amorphous Networks with Adjustable Poisson Ratio from a Simple Triangular Lattice

Abstract

Materials with a negative and tunable Poisson ratio have great potential applications in fracture resistance and energy absorption. However, one material usually exhibits one specific Poisson ratio and a systematic tuning is highly desired. In this study, we design disordered networks with a wide tunable range of the Poisson ratio based on triangular analysis. By distorting the equilateral triangle lattice, the Poisson ratio can be systematically decreased due to the large area change in highly nonequilateral triangles. Analysis further shows that in a nonequilateral triangle, bonds with different lengths play distinct roles: the removal of short bonds can decrease the Poisson ratio, while the removal of long bonds does the opposite. Thus a negative Poisson ratio can be achieved by removing a small amount of short bonds. Moreover, such networks can serve as unit cells to build larger systems with a similar performance. Such auxetic networks are further experimentally realized in both spring and three-dimensionally printed systems, demonstrating the general validity of our analysis and its possible applications in building practical systems.