Transition boundaries and stiffness optimal design for multi-TPMS lattices

Highlights: • The unique function mapping unique TPMS lattice cells can significantly improve the structural performance. • The interface of Multi-TPMS lattice can effectively transfer loads and retard crack propagation. • The stiffness of optimized bending specimen is increased by 31% compared with the traditional TPMS lattice. Nature has skillfully and finely optimized porous structures with specific configurations in different regions according to the service requirements of organisms, thus evolving the heterogeneous structure with multiple functions. In order to further improve the performance and function of the heterogeneous structure, an optimal design method of multi-scale and Multi-TPMS lattices with geometric continuity is proposed in this paper. The geometrical continuity problem of complex transition boundary of Multi-TPMS lattice is solved, and correlation mapping between principal stress direction and lattice type is established. In mesoscopic view, density model is used to represent the effective properties of lattice structure. Macroscopically, the design domain is divided into Stretch- and shear-dominated region according to the principal stress direction. By mapping specific lattice cells in different stress regions, the unique properties of different lattice cells are fully utilized to improve the mechanical properties. The experimental results show that the stiffness and strength of the optimized samples are increased by 31% and 21%, respectively, compared with the traditional TPMS gradient density lattice.