TPMS-based interpenetrating lattice structures: Design, mechanical properties and multiscale optimization

Compared to single-phase structures, interpenetrating lattice structures display the potential to achieve a wide range of tailorable physical and mechanical properties. Herein, we present a novel class of interpenetrating lattice structures based on triply periodic minimal surfaces. Using representative volume elements applied with the periodic boundary conditions, the contributions of the volume fraction and the interpenetrating parameter, a measure of the ratio of the two phases, on the mechanical properties and deformation behavior of the interpenetrating lattice structures are investigated. Results show that the mechanical properties are highly dependent on the interpenetrating parameter, and isotropic elasticity can be achieved at a particular value. Moreover, the uniaxial and shear deformation mechanisms (bending or stretching behavior) can be easily changed by adjusting the interpenetrating parameter. Our new interpenetrating lattice designs are experimentally validated using 3D-printed samples. Finally, a new multiscale optimization framework, based on simultaneously optimizing the distribution of the volume fraction and the interpenetrating parameter, is developed. Compared to the traditional optimized designs that only consider the volume fraction, the proposed optimized design reduces the structural compliance by more than 10.85%, confirming the effectiveness of the proposed optimization framework for lightweight applications.