US-12618331-B2 - Discrete macroscopic metamaterial systems

Abstract

A construction system for mechanical metamaterials based on discrete assembly of a finite set of modular, mass-produced parts. A modular construction scheme enables a range of mechanical metamaterial properties to be achieved, including rigid, compliant, auxetic and chiral, all of which are assembled with a consistent process across part types, thereby expanding the functionality and accessibility of this approach. The incremental nature of discrete assembly enables mechanical metamaterials to be produced efficiently and at low cost, beyond the scale of the 3D printer. Additionally, a lattice structure constructed of two or more rigid, compliant, auxetic and chiral part types enable the creation of heterogenous macroscopic metamaterial structures.

Inventors

• Benjamin Jenett

Assignees

• MASSACHUSETTS INSTITUTE OF TECHNOLOGY

Dates

Publication Date

20260505

Application Date

20240618

Claims (7)

1. 1 . A cuboctahedron cell voxel of a discrete macroscopic lattice system, the cuboctahedron cell voxel comprising: a plurality of cell faces connected to form the cuboctahedron cell voxel; and wherein one cell face of the plurality of cell faces comprises at least one auxetic cell face comprising a plurality of intersecting planes of reentrant mechanisms that form a rectangular arrangement of four corners.
2. 2 . The cuboctahedron cell voxel of claim 1 , wherein each reentrant mechanism resolves uniaxial tension and compression with a lateral expansion and contraction, respectively.
3. 3 . The cuboctahedron cell voxel of claim 2 , wherein the lateral expansion and contraction is a function of an auxetic parameter.
4. 4 . The cuboctahedron cell voxel of claim 3 , wherein the auxetic parameter is a reentrant distance.
5. 5 . The cuboctahedron cell voxel of claim 4 , further comprising a plurality of the auxetic cell faces, wherein each auxetic cell face exhibits a near-zero Poisson's ratio.
6. 6 . The cuboctahedron cell voxel of claim 5 , wherein each auxetic cell face responds to axial strain with a similarly signed transverse strain.
7. 7 . The cuboctahedron cell voxel of claim 4 , wherein the plurality of intersecting planes of reentrant mechanisms comprises: four coplanar nodes, wherein each node is coupled to a distal end of a reentrant mechanism, and wherein a proximal end of each reentrant mechanism joins at a connection point out of plane with the four coplanar nodes.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of priority of (a) U.S. provisional application No. 63/161,251, filed 15 Mar. 2021; and (b) U.S. non-provisional application Ser. No. 17/654,889, filed 15 Mar. 2022, as a Divisional thereof, the contents of both are herein incorporated by reference. BACKGROUND OF THE INVENTION The present invention relates to light weight macroscopic structures and, more particularly, to macroscopic metamaterial systems and methods of assembly. Engineering structures and systems today—from bridges to cars to airplanes—are informed and limited by the materials of which they are made, and the processes used to shape, join, and configure these materials into end products. Scale, cost, and performance are inevitably drivers for the types of structures that exist: the implication being large, high-performance structures are difficult and expensive to build. For instance, turbine blades are relatively cheap, but quickly run into issues at lengths over 50 m. Aircraft are more expensive and require dedicated infrastructure, such as airplanes bigger than airplanes to transport the airplanes. And finally, space structures like the ISS take decades to install and cost billions of dollars, yet ultimately are limited by the material and shaping processes used to make any other given structures on earth. Humans are highly skilled makers, but that does not change the fact that making big things is fraught with challenges. The notion of rationally designing a material from the microscale to the macroscale has been a long-standing goal with broad engineering applications. From the field of material science, the notion first emerged of an artificial material with novel properties controlled by local, cellular design (e.g., electromagnetic metamaterials possess synthetic properties that allows them to interact with electromagnetic waves in ways that naturally occurring materials cannot). Benefits of nanoscale features to further expand the exotic property parameters on the microscopic level have also been explored. In the field of mechanics, a practitioner is interested in controlling separately the elastic constants of an engineered material (modulus of elasticity E, bulk modulus K, shear modulus G, and Poisson's ratio v) to design macroscopic structures. And with the introduction of additive manufacturing, it was finally possible to materialize macroscopic mechanical metamaterials with superior stiffness and strength at ultralight densities with multiscale hierarchy. However, additive manufacture has limits that undermine its use for large scale structures. Namely, the size of three-dimensional printer limits the size of the pieces that can be additively manufactured. In fact, for such larger construction projects, the cost, scalability, and throughput rates of alternative discrete assembly are competitive and, in some cases, better than state of the art additive manufacture, making discrete assembly of metamaterial lattice structures an appealing method for constructing large scale cellular structures. As can be seen, there is a need for macroscopic metamaterial discrete lattice systems and methods of assembly that are scalable, versatile, and reliable. The macroscopic metamaterial systems embodied in the present invention exhibit a new range of attainable properties, such as rigidity, compliance, chirality, and auxetic behavior, all within a consistent manufacturing and assembly framework. These discrete mechanical metamaterials show global continuum properties based on local cellular architectures, resulting in a system with scalability, versatility, and reliability. Furthermore, the macroscopic metamaterial discrete lattice systems of the present invention enable assembly automation through use of mobile robots adapted to operate relative to their discrete material environment. By leveraging the embedded metrology of discrete materials, these relative robots have reduced complexity without sacrificing extensibility, enabling the robots to build structures larger and more precise than themselves. Additionally, multi-robot assembly has cost and throughput benefit at larger scales. The present invention contemplates discretely assembled systems utilizing internal architectures at the macroscopic unit cell level, that can be designed to transmit or respond to load in non-standard ways. For example, auxetic metamaterials exhibit zero or negative Poisson's ratio, wherein internal, re-entrant architectures produce contraction perpendicular to compressive loading, and expansion perpendicular to tensile loading, counter to traditional continuum material behavior. Chiral metamaterials exhibit handedness based on asymmetric unit cell geometry. These designs produce out of plane deformations, such as twist, in response to in plane loading. The unit cell level, called voxel herein, are composed of vertex-connected open face parts to form the cuboctahedra voxel. Each of these