Stiffness optimisation of sandwich structures with elastically isotropic lattice core

Abstract

This study concerns homogenisation-based stiffness optimisation with elastically isotropic plate and truss-based lattice structures. Due to the lattices’ isotropy, an optimised design can be obtained without including each lattice's rotational degree of freedom (DOF) as a design variable. Stiffness optimisation was performed on sandwich structures with lattice cores. Two optimised sandwich structures were fabricated using material extrusion additive manufacturing, and their deformation behaviour was studied using digital image correlation (DIC). DIC results revealed that when using a truss-based lattice as the core, certain trusses were susceptible to local strain concentration. On the other hand, sandwich structures with a plate-based lattice as the core showed an evenly distributed strain field, indicating loads can be more efficiently carried. Optimisation results in a maximum increase of 14.0 % for bending stiffness and 24.2 % for energy absorption. This research stands out for its novel selection of lattices and in-depth analysis of the full-field strain distribution in optimised sandwich lattice structures during bending. Combining experimental and numerical methods, the study sheds light on the deformation mechanism of these additively manufactured lattices, offering additional insights.