Mechanical behavior of a novel lattice structure with two-step deformation

Lattice structures are increasingly attracting attention due to their excellent mechanical properties and broad application prospects. However, most developed lattices feature single-step deformation or single plateau stress, which confine its multi-task applications. Herein, a novel body-centered cubic (NBCC) with two-step deformation based on body-centered cubic (BCC) and bionic fractal design is introduced. NBCC exhibits bi-plateau stress in the stress–strain curves. The underlying mechanism is caused by the bending and buckling deformation of the struts. The mechanical behaviors of NBCC are investigated by finite element simulation which verified by experiment. Compared with traditional BCC, NBCC has improved modulus of elasticity by 88 %, yield strength by 21.2 %, and specific energy absorption by 108 % when ρ′ and α are 0.07 and 0.5, respectively. Moreover, the elastic modulus as well as yield strength increase with geometrical ratio α. The specific energy absorption tends to maximum at the geometric ratio α = 0.6 ∼ 0.7. From the Ashby map, the proposed NBCC lattice possesses high energy absorption, exceeding most of the existing architected materials at the same density. Furthermore, the results show that NBCC has better isotropy of elastic modulus and tends to be more isotropic material compared to BCC. Finally, theoretical model of two-step plateau stress is established based on hinge dissipation principle. This work opens up new insights into the use of element replacement design to create multi-step pathways that can be applied to design engineering structures with multiple tasks and application for impact protection.