Abstract
Breakthroughs in fabrication techniques enabled the creation of microlattice materials, which are assembled from truss-like elements on the micro-scale. The mechanical properties of these materials can be controlled varying the geometry of their microstructure. Here, we study the effect of topology and effective density on the visco-elastic properties of microlattices fabricated by direct laser writing. We perform micro scale relaxation experiments using capacitive force sensing in compression. The experimental results are analyzed using a generalized Maxwell model and the viscoelastic properties are studied in terms of density scaling laws. We develop a finite element model that allows extracting the bulk polymer viscoelastic properties. The experimental results show that the stiffness of lattice materials can be adjusted independently from the loss factor in a wide range of frequencies. We find that the loss factor dramatically increases with applied strain due to the onset of nonlinear dissipation mechanism such as buckling and plasticity. We show that at effective densities around 50% the energy dissipation per cycle in a microlattice outperforms the dissipation in the bulk, giving rise to a “less is more” effect. The present research defines a first step in the application of microlattice materials in vibration absorption.
Highlights
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Breakthroughs in fabrication techniques enabled the creation of microlattice materials, which are assembled from truss-like elements on the micro-scale
We study the effect of topology and effective density on the visco-elastic properties of microlattices fabricated by direct laser writing
Summary
In our work we focus on the control of mechanical properties by adjusting the microstructure, apart from the possibility of controlling their properties by changing the polymer base or degree of polymerization [15]. The amplitude of the wrinkles is approximately 0.1 μm with a wavelength of 0.35 μm Another aspect of the writing process is the residual deformation due to residual stresses, which can be observed by slightly curved vertical edges of the microlattice structures. This aspect will be neglected in the analysis. The chosen truss radii result in effective densities between 8% and 65% for stretch dominated structures and 4% and 45% for bending dominated structures respectively (see Fig. 2(a), (b)). The resulting effective densities of the SD structures are larger at equal radius due to the higher number of trusses per unit cell and the higher connectivity of trusses. The minimum radius is restricted by structural stability, while the maximum radius is set close to the merging of individual trusses
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