Multi-material 3D printed mechanical metamaterials: Rational design of elastic properties through spatial distribution of hard and soft phases

Abstract

Up until recently, the rational design of mechanical metamaterials has usually involved devising geometrical arrangements of micro-architectures that deliver unusual properties on the macro-scale. A less explored route to rational design is spatially distributing materials with different properties within lattice structures to achieve the desired mechanical properties. Here, we used computational models and advanced multi-material 3D printing techniques to rationally design and additively manufacture multi-material cellular solids for which the elastic modulus and Poisson's ratio could be independently tailored in different (anisotropic) directions. The random assignment of a hard phase to originally soft cellular structures with an auxetic, zero Poisson's ratio, and conventional designs allowed us to cover broad regions of the elastic modulus-Poisson's ratio plane. Patterned designs of the hard phase were also used and were found to be effective in the independent tuning of the elastic properties. Close inspection of the strain distributions associated with the different types of material distributions suggests that locally deflected patterns of deformation flow and strain localizations are the main underlying mechanisms driving the above-mentioned adjustments in the mechanical properties.

Hinged-3D metamaterials with giant and strain-independent Poisson’s ratios

“…Unlike existing designs of metamaterials 22,[27][28][29]32,33 , our proposed metamaterial is of constant Poisson's ratios. In our metamaterial, the transverse displacement is directly proportional to the applied longitudinal displacement.…”

“…Whereas previous studies proposed metamaterials with giant Poisson's ratios 22,[27][28][29]32,33 , the Poisson's ratio being tailorable as the applied strain increases is a must. For example, the Poisson's ratio of microporous foam varied between ∼1 and −12 when increasing the applied strain from 2% to 35% 22 .…”

“…Recent studies demonstrated giant negative Poisson's ratios of artificial metamaterials with microlattices of dissimilar materials 32 . For instance, 3D printed-multimodulus metamaterials gave −7 Poisson's ratio 32,33 .…”

“…Recent studies demonstrated giant negative Poisson's ratios of artificial metamaterials with microlattices of dissimilar materials 32 . For instance, 3D printed-multimodulus metamaterials gave −7 Poisson's ratio 32,33 .Whereas previous studies proposed metamaterials with giant Poisson's ratios 22,[27][28][29]32,33 , the Poisson's ratio being tailorable as the applied strain increases is a must. For example, the Poisson's ratio of microporous foam varied between ∼1 and −12 when increasing the applied strain from 2% to 35% 22 .…”

Accelerating Auxetic Metamaterial Design with Deep Learning

“…Aside from the pressure‐driven actuation control system, in many of these cases, the only way for the intricate structures to be manufactured is through detailed casting or, as we use in our approach, via an additive manufacturing system. Additive manufacturing is an ideal method of creating various types of metamaterials because 3D printers are capable of fabricating complex architectures . The coupled ability to rapidly and iteratively discover new designs with machine learning and experimentally validate results with additive manufacturing marks a novel discovery process in manufacturing and materials characterization .…”