Exploring the mechanical properties of bending- and stretching-dominated metamaterials

Nature has always had randomness in many ways. Natural cellular structures, specifically, have used randomized microarchitectures to form mechanically efficient materials, such as wood, sponge, and trabecular bone. Mechanical metamaterials are a class of artificial microarchitected materials designed to carry tensions and compressions with...

Toolpath Generation for Fused Filament Fabrication of Functionally Graded Materials

The products in our day to day lives have different requirements in different regions of the product. One way of dealing with such spatially varying requirements is to divide the product into multiple parts and assign each part a different material. For example, the handle of a drill is often fitted with a rubbery material which gives it more...

Active mechanical metamaterial unit cell with integrated piezoelectric stack actuator

Metamaterials are engineered structures that exhibit exotic properties that are obtained from the unit cell geometry and arrangement instead of its constituent materials. Mechanical metamaterials alter mechanical stimuli and they can exhibit unique elastic properties such as negative stiffness, shear modulus, bulk modulus, and Poisson’s ratio....

Curvature Induced by Deflection in Thick Meta-Plates

The design of advanced functional devices often requires the use of intrinsically curved geometries that belong to the realm of non-Euclidean geometry and remain a challenge for traditional engineering approaches. Here, it is shown how the simple deflection of thick meta-plates based on hexagonal cellular mesostructures can be used to achieve...

Femur auxetic meta-implants with tuned micromotion distribution

Stress shielding and micromotions are the most significant problems occurring at the bone-implants interface due to a mismatch of their mechanical properties. Mechanical 3D metamate-rials, with their exceptional behaviour and characteristics, can provide an opportunity to solve the mismatch of mechanical properties between the bone and...

Idealized 3D auxetic mechanical metamaterial: An analytical, numerical, and experimental study

Mechanical metamaterials are man-made rationally-designed structures that present un-precedented mechanical properties not found in nature. One of the most well-known mechanical metamaterials is auxetics, which demonstrates negative Poisson’s ratio (NPR) behavior that is very beneficial in several industrial applications. In this study, a...

Elasticity Approach to Predict Shape Transformation of Functionally Graded Mechanical Metamaterial under Tension

The re-entrant structures are among the simple unit cell designs that have been widely used in the design of mechanical metamaterials. Changing the geometrical parameters of these unit cell structures, their overall elastic properties (i.e., elastic stiffness and Poisson’s ratio), can be simultaneously tuned. Therefore, different design...

Active metamaterials: unit cells for tunable damping

The concept of metamaterials has been extended from electromagnetics and acoustics to the field of mechanics. Metamaterials do not derive their properties from those of the composite, but from the artificial meso-scale geometry as well as from the unit cell structure. Mechanical metamaterials are constrained in that the mechanical properties are...

Application of mechanical metamaterials in a parametric, 3D printed ankle foot orthosis

During this project the possibilities of enriching the functionality of an Ankle Foot Orthosis (AFO) by implementing mechanical metamaterials are researched. The project is executed for Buchrnhornen, a company based in Eindhoven which has over 70 years of experience in manufacturing orthopaedic shoes and orthosis in a traditional way. Mechanical...

Spatial pseudo-rigid body model for the analysis of a tubular mechanical metamaterial

In this paper, a pseudo-rigid body model is proposed for the analysis of a spatial mechanical metamaterial and its application is demonstrated. Using this model, the post-buckling behavior of the mechanical metamaterial can be determined without the need to consider the whole elastic structure, e.g., using finite-element procedures. This is done...

Mechanical Metamaterials by Topology Optimization

Auxetic materials exhibit material properties, which are usually not seen in nature. This type of materials belong to the class of mechanical metamaterials and can be used for e.g. energy absorption, cloaking of objects, shape morphing applications and the design of fiber-reinforced composites. They exhibit a negative Poisson’s value and derive...

Design of a Super-Compressible Metamaterial: An Experimental Investigation Guided by Machine Learning

Mechanical metamaterials are a new emerging class of materials which achieve properties outside the bounds of conventional materials. A metamaterial consists of a unit cell which is periodically repeated in space. In this study, a new metamaterial unit cell is proposed, derived from a class of space structures known as deployable masts. What...

Non-auxetic mechanical metamaterials

The concept of "mechanical metamaterials" has become increasingly popular, since their macro-scale characteristics can be designed to exhibit unusual combinations of mechanical properties on the micro-scale. The advances in additive manufacturing (AM, three-dimensional printing) techniques have boosted the fabrication of these mechanical...

2D Lattice Materials for Actuation

Externally triggered lengthening or shortening (actuation) of one or more members in a lattice material can be used to achieve macroscopic shape changes. The three main attributes looked for in 2D lattice materials to be deemed suitable for actuation are in-plane isotropy, high specific elastic properties and limited energy requirement for...

Green's function molecular dynamics approach: Proportionality between area and load

The rational design of meta-implants using a combination of auxetic and conventional microstructures

With the aging population growing, the increasing prevalence of osteoarthritis (OA) seems inevitable. As a result, the number of joint replacements is expected to grow substantially within the next decade. Today’s hip replacements have the potential to function for more than 20 years, but due to risk factors such as aseptic loosening, the...