Tensile behavior of an auxetic structure: Analytical modeling and finite element analysis

Auxetic materials possess the fascinating property of expanding laterally when stretched longitudinally. However, previous investigations into behavior under large deformation of such materials in tension have been very limited. This work systematically analyses the tensile behavior beyond yield of re-entrant hexagonal honeycombs in the two principal directions. Analytical modeling is performed by considering the plastic, nonlinear behavior of cell walls based on idealized mechanisms. The analytical results are compared with those of the corresponding finite element simulations. Two material models have been studied, a rigid-perfectly plastic material model and that with strain hardening. Plastic Poisson's ratio is calculated as the ratio of the incremental strains in the two perpendicular directions and this ratio changes significantly, from negative to positive, for the re-entrant honeycombs in tension. The elastic slope of stress-strain curves is also considered and initial yielding point is determined. The influences of various geometrical and material parameters on the response of re-entrant honeycombs are discussed. (C) 2017 Elsevier Ltd. All rights reserved.