Three-dimensional cellular materials are ubiquitous in nature. These materials have found use in a variety of engineering applications credit to their excellent mechanical properties, such as: light weight, low moduli and large variation of Poisson’s ratio, which are usually inaccessible with ordinary materials. As a result, these materials have been widely studied. A particular category of cellular structures is the chiral cellular structure that cannot mirror itself by translations and rotations alone. Fortunately, as a phenomenon ubiquitous in nature, chirality has already been studied in many branches of science. Nonetheless, in recent years, chiral cellular structures with novel and unique properties have attracted growing interest from both scientists and engineers in the field of composite materials and structures. Consequently, various types of chiral cellular structures have been investigated on their mechanics and potential applications. Existing literature has reported that the chiral cellular structures exhibit considerable compliant behavior, which makes them good candidates for flexible structures in precision engineering, morphing aircraft design – among others.
Different from the widely studied chiral structures, the missing-rib cellular structure, composed of four V-shaped wings intersecting at the center of the unit cell, owns a distinct novel topology, and also exhibits chirality with great potential in engineering applications. Regardless, there exists little literature on the elastic properties of the missing-rib structure. Generally, there is need to study the 2D chiral cellular structure with more geometric parameters so as to enrich the structural configurations. On this account, researchers from Hohai University in China: Professor Weidong Liu, Master Honglin Li, Master Zhendong Yang and Dr. Xinfeng Ge, in collaboration with Dr. Jiong Zhang at the Wuyi University assessed the in-plane mechanics of the 2D chiral structure with more geometric parameters using a simple and robust way. Their work is currently published in the research journal, Engineering Structures.
In their approach, the structure was presented by employing the parameters of the constituting ribs of the V-shaped wings, and then the in-plane mechanical properties of the structure were investigated through energy-based method and verified through finite element (FE) analysis. The effects of the geometrical parameters on the relative elastic and shear moduli, the maximum global-local strain ratios and the coupling effects of the structure were also concretely discussed.
The research team reported that the equivalent moduli of the structure can be several orders of magnitude lower than those of the base material, and the maximum global strains can be dozens of times those of the base material. Besides, the structure showed significant in-plane elastic coupling effects: the maximum ratio of the shear to elastic strain beyond 17.2°/% and the maximum ratio of the elastic to shear strain exceeding 1.52%/° (x-direction) and 1.64%/° (y-direction).
In summary, the study presented an in-depth investigation of the in-plane elasticities of the 2D chiral cellular structure with V-shaped wings based on the energy method and verified by FE analysis. The structure studied in this paper exhibited low in-plane moduli as well as large maximum global-local strain ratios, which indicated considerable in-plane elasticities and morphing capabilities. In a statement to Advances in Engineering, Professor Weidong Liu, the corresponding author said that the investigated 2D chiral structure showed great potential as a candidate selection for flexible structures in engineering applications.
Weidong Liu, Honglin Li, Zhendong Yang, Jiong Zhang, Xinfeng Ge. In-plane elastic properties of a 2D chiral cellular structure with V-shaped wings. Engineering Structures, volume 210 (2020) 110384.