Structurally Efficient Three-dimensional Metamaterials with Controllable Thermal Expansion

Abstract

The coefficient of thermal expansion (CTE) of architected materials, as opposed to that of conventional solids, can be tuned to zero by intentionally altering the geometry of their structural layout. Existing material architectures, however, achieve CTE tunability only with a sacrifice in structural efficiency, i.e. a drop in both their stiffness to mass ratio and strength to mass ratio. In this work, we elucidate how to resolve the trade-off between CTE tunability and structural efficiency and present a lightweight bi-material architecture that not only is stiffer and stronger than other 3D architected materials, but also has a highly tunable CTE. Via a combination of physical experiments on 3D fabricated prototypes and numeric simulations, we demonstrate how two distinct mechanisms of thermal expansion appearing in a tetrahedron, can be exploited in an Octet lattice to generate a large range of CTE values, including negative, zero, or positive, with no loss in structural efficiency. The novelty and simplicity of the proposed design as well as the ease in fabrication, make this bi-material architecture well-suited for a wide range of applications, including satellite antennas, space optical systems, precision instruments, thermal actuators, and MEMS.

Enhanced thermal conductivity of epoxy composites filled with silicon carbide nanowires

“…In order to fabricate composites with superior thermal conductivity, beside the amount of filler, uniform dispersion in polymer matrix is the critical factor 35 . We adopted a transient laser flash method to indirectly estimate the thermal conductivity of the neat epoxy and its composites at room temperature.…”

Origami Metamaterials for Tunable Thermal Expansion

“…The experimental results shown as markers in Figure 2a,b reveal an important feature of our system: the coefficient of thermal expansion can be tuned in situ by varying the opening angle. [6,14,15] Finally, we note that δ has almost no effect on design #A, which is always characterized by negligible area changes. This marks a difference with previously proposed concepts, whose response is characterized by fixed coefficients of thermal expansion, that are typically extremely difficult to tune and control after the assembly.…”

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materials, which include 2D [6][7][8][9][10] and 3D [11][12][13][14][15] multimaterials lattices as well as bi-materials microstructures, [16,17] are all porous and characterized by a response that is very difficult to be tuned after manufacturing.Origami-the ancient art of paper folding-not only leads to aesthetically pleasant structures but also enables the design of materials with novel mechanical properties, including negative and adjustable Poisson's ratio, [18][19][20][21] programmable curvature [22] and mechanical response, [23] and multistability. [24] Here, we focus on a simple origami tessellation, the Miuraori, [25] and combine experiments with simulations to demonstrate that this system can also provide a platform for the design of materials with a wide range of coefficients of thermal expansion.

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“…materials, which include 2D [6][7][8][9][10] and 3D [11][12][13][14][15] multimaterials lattices as well as bi-materials microstructures, [16,17] are all porous and characterized by a response that is very difficult to be tuned after manufacturing.…”

Thermomechanically Tunable Elastic Metamaterials With Compliant Porous Structures

“…The other approach for designing metamaterials with NTE is in construction with triangular or tetrahedron unit cells with multimaterial truss members, causing different principal strains in response to temperature leading to macroscopic shearing [35,50]. Indeed, triangulated structures have an excellent structural performance-high specific modulus and strength with elastic isotropy.…”