The integration of lattice structures into parts using powder bed fusion of metals using a laser beam (PBF-LB/M) allows tailoring mechanical properties by adjusting their geometric parameters. A composite material created by filling the voids in the lattice structures with a second, viscoelastic material offers promising dynamic properties. However, understanding the relationship between the lattice geometry and the resulting dynamic mechanical behavior is essential for designing composite materials and applying them to industrial components, such as boring bars. This study investigated the dynamic structural behavior of various strut- and wall-based lattice structures filled with epoxy resin. Lattice structures were integrated into IN718 beams manufactured by PBF-LB/M. Experimental modal analyses were conducted to evaluate the changes in the eigenfrequency, the dynamic compliance, and the damping ratio before and after the filling. Microscopic and cross-sectional analyses supported examinations. The results showed that the unit cell size and the volume fraction significantly influence the infiltration. In addition, the eigenfrequency and the dynamic compliance can be effectively adjusted by changing the volume fraction. In particular, the epoxy resin filling had a large effect on the damping ratio and increased it by a factor of up to 3.6 for the body-centered cubic cell. Among all the studied lattice types, the diamond TPMS structure had the highest eigenfrequency and the lowest dynamic compliance. From the results of the statistical evaluation, recommendations of action for the design of composite lattice structures were derived.

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.

Vibrationsanfällige Werkzeuge, wie z. B. lange und dünne Bohrstangen, weisen aufgrund einer erhöhten dynamischen Beanspruchung eine reduzierte Lebensdauer im Vergleich zu schwingungsresistenten Strukturen auf. Die Integration passiver Dämpfungsstrukturen in die Werkzeuge kann diese Herausforderung lösen. Das Laser-Strahlschmelzen (PBF-LB/M) ermöglicht diese Funktionsintegration und die Herstellung geometrisch komplexer Strukturen. Im Forschungsprojekt „AM Damping Microstructures“ werden daher additiv gefertigte Dämpfungsstrukturen untersucht, um das Dämpfungsverhalten vibrationsanfälliger Bauteile gezielt einzustellen. Die Ergebnisse in dieser Arbeit vergleichen das Dämpfungsverhalten und die dynamische Nachgiebigkeit unterschiedlicher Konzepte.