Crystal-twinning inspired lattice metamaterial for high stiffness, strength, and toughness

Abstract

Inspired by the strengthening mechanism of crystal twinning boundary, this work proposes a novel strategy for lattice metamaterial design to improve stiffness, strength, and toughness. At the microscale, the inclination variable of unit-cell is introduced into the analytical formula of modulus in the compression direction. Then, the mechanical constitutive model of lattice structure with the inclination variable is established, which can be used to obtain the optimized inclination angle and maximize the stiffness in the compression direction. At the scale of periodic macro-array, to achieve the best mechanical properties in the compression direction without sacrificing the mechanical properties in the horizontal direction, twinning boundaries are introduced into both horizontal and vertical directions of the structure. Additionally, the mechanical properties of the structure can be further improved by controlling the number of twinning boundaries. The models are then fabricated through additive manufacturing and compressed. The experimental and simulation results show that the proposed method can simultaneously improve the stiffness, strength, and toughness of the lattice structure. For example, the stiffness of the optimized SC-BCC lattice structure is improved by 50.82%, the strength by 10.94%, and the energy absorption performance by 20.06% in the compression direction.

Keywords

• Lattice metamaterial design
• Crystal twinning boundary
• Enhanced strength, stiffness, and toughness
• Multi-scale design
• Novel lattice