Mechanics of curved chiral beam based three-dimensional metamaterial

Abstract

Flexible metamaterials with low modulus but progressively enhanced compressive resistance have shown huge potential in flexible protection applications for personnel and sensitive equipment. Ascribed to the specific mechanical properties such as negative Poisson's ratios and significant compressibility, the chiral microstructural configurations have attracted great interests in energy absorption and can therefore be customized for specific designs. However, the more advanced design is still desired. In this paper, a three-dimensional curved chiral beam based lattice (3D-CCBL) was proposed by replacing the conventional straight trusses with curved chiral beams, aiming to achieve novel metamaterial with excellent flexibility and tailorable mechanical properties. Two types of 3D-CCBL specimens, with arc angles ranging from 120° to 210° were fabricated using the selective laser sintering (SLS) additive manufacturing technique. The compressive characteristics of 3D-CCBL were thoroughly investigated via experiments and simulations, considering the effects of anisotropy and relative density. In addition, a theoretical model was derived to predict the compressive modulus and plateau stress of 3D-CCBL, which achieved satisfactory agreement with both experimental measurements and numerical predictions. It is indicated that both types of 3D-CCBL mainly exhibited a bending-dominated deformation mode, although type II of 3D-CCBL possessed better energy-absorbing capacity and resistance to instability. The energy-absorbing capacity of 3D-CCBL can be enhanced by appropriately decreasing the arc angle, whereas the small angles would be more likely lead to instability. This paper provides a framework for guiding the design of three-dimensional flexible and ultra-lightweight metamaterials and promotes their applications in the fields of flexible protections.