  Particle dampers represent a simple yet effective means to reduce unwanted
oscillations when attached to structural components. Powder bed fusion additive
manufacturing of metals allows to integrate particle inclusions of arbitrary
shape, size and spatial distribution directly into bulk material, giving rise
to novel metamaterials with controllable dissipation without the need for
additional external damping devices. At present, however, it is not well
understood how the degree of dissipation is influenced by the properties of the
enclosed powder packing. In the present work, a two-way coupled discrete
element - finite element model is proposed allowing for the first time to
consistently describe the interaction between oscillating deformable structures
and enclosed powder packings. As fundamental test case, the free oscillations
of a hollow cantilever beam filled with various powder packings differing in
packing density, particle size, and surface properties are considered to
systematically study these factors of influence. Critically, it is found that
the damping characteristics strongly depend on the packing density of the
enclosed powder and that an optimal packing density exists at which the
dissipation is maximized. Moreover, it is found that the influence of
(absolute) particle size on dissipation is rather small. First-order analytical
models for different deformation modes of such powder cavities are derived to
shed light on this observation.
