Damping capability of lattice structures: a numerical study

Lattices are recognized as ultra-lightweight materials with high specific stiffness and high specific strength. The applications of this architectural material range from the aerospace and automotive industry up to the biomedical one. In the literature, most of the studies address the mechanical responses of lattice structures under static, dynamic (impact) and fatigue loading conditions while only few works deal with the damping capabilities of such structures. This study focuses on the damping capability of classical lattice configurations whose architecture is made of struts (i.e. CC, CBCC, ACC, Octet, Rhombic dodecahedron). The influence of three aspects has been investigated: the geometrical parameters defining the structure of the lattice cell, the introduction of a compressive pre-stress field within the cell and the plastic constitutive behaviour of the material used for the struts. A broad sensitivity campaign has been performed in order to evaluate the amount of dissipated energy for the different cell architectures according to the variation of the strut diameter and to the presence of local instabilities (post-buckling behaviour of the struts). In order to perform the sensitivity analyses, two general modelling strategies have been developed. The first one is intended for a linear elastic material behaviour. In this case, the strategy comprises four phases: 1) an eigenvalue buckling analysis, 2) a non-linear buckling analysis, 3) a pre-stress modal analysis and 4) an harmonic analysis. The second modelling strategy has been developed when a non-linear plastic behaviour is assigned to the struts material. The phases of the numerical strategy change into: 1) an eigenvalue buckling analysis, 2) a non-linear buckling analysis and 3) a non-linear transient analysis with pre-stress. The numerical results highlight how the damping capability of the considered cell, for the same loading condition, is strongly related to the topology of the cell and to its relative density. By smartly tailoring these parameters, the damping capability without pre-stress can be increased up to 32% and, if the pre-stress is introduced within the cell, the damping effects can intensified up to 60%.