The effect of defects and missing connections on the Poisson’s ratios and other properties of cellular systems with particular reference to their auxetic potential

Abstract

Auxetics are systems which exhibit a negative Poisson’s ratio, i.e. get fatter when stretched and thinner when compressed. This anomalous behaviour is manifested in several honeycombs and cellular structures and may be explained in terms of various geometry / deformation mechanism based models. In particular, it has been proposed that auxetic behaviour may be obtained from re-entrant honeycombs which deform through hinging and/or hinging of the cell walls [1], rotation of rigid units [2,3] as well as mechanisms which involve selective removal of ribs in conventional honeycombs (missing ribs model) [4]. This work investigates the effect that defects have in cellular systems, in particular, how the removal of some structural unit within an auxetic or conventional system affects the mechanical properties, in particular the Poisson’s ratios.