I do research on the field of mechanical behavior of materials, and more precisely mechanical metamaterials. Mechanical metamaterials are structures, or spatially architected materials, such as lattices, with unique mechanical properties that cannot be found in nature. I investigate metamaterials for energy absorption, high specific strength, or wave filtering. To conduct research I combine different tools, like analytical models, simulations (finite element analysis), advanced manufacturing, and experimental analysis.
Using negative stiffness elements we can design metamaterials that absorb energy; or metamaterials that have multiple stable configurations with different acoustic properties.
Negative stiffness is the reverse of the positive stiffness. Positive stiffness is the ability to resist deformation under stress. A material with negative stiffness will aide the deformation, instead of opposing it. Negative stiffness is by itself unstable, but there are elements that can present a negative stiffness phase, like two tilted pin-joined springs, or ached shaped beam.
An example of this concept is the bottom of an aluminum can (i.e. a dome-shaped membrane). If we press the middle of the bottom of a can, at first it will oppose the deformation, but at a certain force it will pop and invert its original shape. This sudden pop is a negative stiffness phase, as the membrane deformed from one configuration to another without resisting.
Energy Absorption is an important mechanical property to design dampers, helmets, or crumple zones of cars, to name a few applications. We can design metamaterials with negative stiffness elements that absorb energy repeatedly, and/or filter vibrations.
Another type of metamaterials that I investigate are nanolattices with high specific strength (strength per unit weight), and/or high energy absorption for impact protection.
Nanolattices are structures with nanometer-size members. A material can be many times stronger in the nanoscale than in regular dimensions. Manufacturing lattices at the nanoscale aims to exploit beneficial size effects to make metamaterials with superior strength.
By synthesizing nanolattices formed by a shell with homogeneous curvature, like spinodal topology (picture), we can achieve a metamaterial that maintains a high strength for prolonged deformations. Thus, when crushed, nanospinodals absorb a lot of energy.