Mechanical characterization of hollow ceramic nanolattices

Reexamining the mechanical property space of three-dimensional lattice architectures

“…In solid-beam lattices, the nodes form solid joints that hinder beam rotation, shortening the effective length of the constituent beams and generally leading to higher stiffnesses. While beam models that capture shearing behavior, such as Timoshenko models, can be used to more accurately capture the behavior of short beams [20,46], they lead to a drop in the effective stiffness, which is opposite from the trend observed here. Accurately replicating the mechanics of solid lattices with computationally efficient models, similar to what is done using beam elements, requires in-depth investigations into the role of nodes on the mechanical properties, which is outside the scope of this work.…”

“…The non-rigid tetrakaidecahedron lattices accommodate macroscopic deformation through local deformation at the nodes ( Figure 4D), which causes them to be sensitive to nodal compliance and less sensitive to the beam waviness. The primary imperfections at the nodes exist in the form of misalignment [15], which have a minimal effect on the stiffness [20] and lead to an agreement between FE and experimental results across the tested range of relative densities. The effect of beam waviness has been quantified in the Supplementary Materials.…”

“…This degradation in mechanical properties is greater than what is observed even in stochastic materials, suggesting that it can have a hugely detrimental role on lattice stiffness. Nodal misalignment is the most common form of imperfection in lattices fabricated here [20]. In lattices with offset nodes, no observable change in the stiffness occurred, with only a minimal change in the yield strength, which had a ~22% decrease in strength for the most heavily distorted lattice.…”

“…These materials are 3D assemblies of beams with micro-and nanoscale constituent dimensions, and it is the confluence of nanometer-sized dimensions and architecture that gives rise to their unique properties [1][2][3]15,[18][19][20][21][22][23][24][25][26]. The theoretical maximum Young's modulus ‫)ܧ(‬ and yield strength (ߪ ௬ ) of a lightweight porous material are set by the Voigt bound, which are functions of the relative density (ߩ̅ ) as ‫ܧ‬ = ‫ܧ‬ ௦ ߩ̅ and ߪ ௬ = ߪ ௬௦ ߩ̅ .…”

3D nano-architected metallic glass: Size effect suppresses catastrophic failure

“…Nanolattices, or architected structural metamaterials, exhibit hierarchical ordering ranging from nanometer length scales in wall thickness to micron length scales in defining unit cells and beyond millimeter scales in the overall macroscale architecture, with many nano-architectures produced by using direct-laser-writing two-photon lithography [14][15][16][17]. Existing work on nanolattices has primarily focused on hollow ceramic nanolattices [18][19][20][21][22], due to the ease of depositing conformal coatings of ceramic materials by atomic layer deposition (ALD) and the M A N U S C R I P T 4 inertness of these ceramic materials to oxygen plasma, which has thus far been the plasma of choice for etching away the internal polymer scaffold to produce nanolattices. One of the key findings from these studies is that by optimizing the wall thickness-to-radius ratio of the nanolattice beams, hollow alumina nanolattices can recover to their original shape after compression in excess of 50% strain [20].…”