An auxetic honeycomb structure with series-connected parallograms

•A new NPR 2D honeycomb was developed based on the horizontal series-connected parallelograms.•A combination of analytical, numerical and experimental method was adopted to investigated the in-plane effective modulus of the new 2D honeycomb.•Dependence of the mechanical properties of the new 2D homeycomb on the geometric parameters was exploited.•New mechanism for generating NPR was discovered.•The new 2D honeycomb was extended to three dimensions. This paper details a new 2D auxetic honeycomb that was structured by mirroring the horizontal series-connected parallelograms along the vertical direction. A combination of analytical, numerical, and experimental methods was used to gain a deep understanding of the elastic behavior of the new honeycomb and examined its dependence on the geometric parameters. The results showed that the new honeycomb can achieve a negative Poisson's ratio via a novel mechanism. Furthermore, the newly developed 2D honeycomb was extended to three dimensions, and three kinds of 3D structures were conceived via different splicing methods. A preliminary numerical study was conducted to explore the mechanical properties of the 3D structures. An auxetic effect was found in two principal orthogonal coordinate directions of those 3D structures when they were compressed along the other principal axis. This work may provide a new insight into the design of both the 2D and 3D auxetics.