Buckling-stretch-buckling dominated hybrid mechanical metamaterials fabricated from 3D-printed photopolymer: Design and investigation for enhanced multifunctional mechanical characteristics

With additive manufacturing, lattice structures have become advanced frameworks, and hybrid lattice structures, a type of mechanical metamaterial, can be used for lightweight and impact-resistant materials. In this paper, we present a novel study that solves the global buckling problem by dividing the lattice structure into three layers and combining them based on the mechanical properties that are stretch- and bending-dominated structures. Stretch-dominant structures are in the middle layer, while bending-dominant structures are at the top and bottom. Octets, Iso-trusses, and Truncated cubes are hybridized with benchmark structures like BCC, FCC, and Kelvin, and additively manufactured using stereolithography to create mechanical metamaterials. A support vector machine (SVM) model was used to predict the peak load, force-displacement response, compressive strength, and energy absorption of all lattice structures under uniaxial compression. The hybrid lattice structure (FCC and Truncated cube) increased the peak load, compressive strength, and energy absorption by 15 %, 18 %, and 20 %, respectively, as compared to uniform lattices. Kelvin and Iso-truss hybrid lattice structures endure peak loads better than Kelvin uniform lattices. BCC and Truncated cube hybrid lattice structures absorb more energy and higher compression modulus than BCC. Designed hybrid mechanical metamaterials are multifunctional due to their global buckling resistance as compared to uniform structures. When compared with the analytical model, FCC and Truncated cube hybrid lattice structure exceed compressive modulus by 4 times that of the uniform lattices. SVM made accurate predictions with an average error of 3.2 %, 6.3 %, and 1.5 % for the peak force, compression modulus, and energy absorption, respectively.