Buckling optimization of Kagome lattice cores with free-form trusses

Highlights: • A novel free-form shape optimization method is presented to increase the buckling loads of lattice cores. • The shape-optimized trusses maintain smooth cross-sectional profiles and eliminate stress concentrations at truss joints. • FE models show 26.8% and 20.4% improvements of the critical buckling loads for 1D clamped columns and 3D Kagome cores. • Compression tests on 3D printed specimens validate the numerically predicted improvements of the buckling loads. Lightweight lattice structures are an important class of cellular structures with high potentials for multi-functional applications. Considering load-bearing requirements, truss buckling is one of the main failure mechanisms for low density and slender lattice structures. Critical buckling loads can be increased by modifying the profile of a truss. In this paper, we present a shape design method to optimize the critical buckling loads for lattice cores with free-form trusses. The free-form truss is represented by Fourier series and implicit surfaces, having smooth truss diameter variations and truss joints. The optimized truss profile is obtained by solving a parametric shape optimization problem with Fourier series coefficients as design variables. The method is used for designing optimized 1D columns and 3D Kagome lattice cores for sandwich panels. The numerical results predict 26.8% and 20.4% improvements of the critical buckling loads for 1D columns and 3D Kagome lattice cores compared to their uniform counterparts of the same mass, respectively. The optimized structures include complex smooth and curved geometries that are well suited for additive manufacturing because of the greater design freedom. Finally, the initial and optimized lattice cores are additively manufactured and tested. The experimental results validate the effectiveness of the proposed method.