Modulating poisson’s ratio in flexible honeycombs by density and architecture gradations

Abstract

Zero Poisson’s ratio structures are a new class of mechanical metamaterials wherein the absence of lateral deformations allows the structure to adapt and conform their geometries to desired shapes with minimal interventions. These structures have gained attention in large deformation applications where shape control is a key performance attribute, with examples including but not limited to shape morphing, soft robotics, and flexible electronics. The present study introduces an experimentally driven approach that leads to the design and development of (near) zero Poisson’s ratio structures with considerable load-bearing capacities through concurrent density and architecture gradations in hybrid honeycombs created from hexagonal and re-entrant cells. The strain-dependent Poisson’s ratios in hexagonal and re-entrant honeycombs with various cell wall thicknesses have been characterized experimentally. A mathematical approach is then proposed and utilized to create hybrid structures wherein the spatial distribution of different cell shapes and densities leads to the development of honeycombs with minimal lateral deformations under compressive strains as high as 0.7. Although not considered design criteria, the load-bearing and energy absorption capacities of the hybrid structures are shown to be comparable with those of uniform cell counterparts. Finally, the new hybrid structures indicate lesser degrees of instability (in the form of cell buckling and collapse) due to the self-constraining effects imposed internally by the adjacent cell rows in the structures.

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions

“…[10,38,39] Moreover, the processing simplicity of TPU-based nanocomposites makes them a suitable polymer candidate for fabricating complex cellular structures with large elongation-to-failure. [39][40][41][42] In addition, the resilience of TPU to abrasion, wear, and environmental conditions makes it well-suited for developing strain sensors that must endure significant deformation with multifunctional capabilities. [33,43] Several fabrication techniques, such as melt mixing, solution blending, and in situ polymerization, have been reported to integrate nanofillers in polymer matrices.…”