4D-Materials & Structures: Using Space-Time Variation to Tailor Structural Properties (2006-2008)
What happens with the effective (i.e. overall / homogenized) properties of a material or structure whose local properties are modulated in both space and time - i.e. in “four dimensions”/4D - and how could this possibly be utilized?
This project combines recent research by the applicants into new ways of creating materials and structures, whose effective dynamic properties can be adjusted “by turning a knob”. They combine that 1) structures can be synthesized with a spatial distribution of material(s) giving specified dynamic properties (e.g. frequency response or stopband locations); and that 2) simple high-frequency mechanical excitation can be used to change effective structural properties (e.g. stiffness and energy dissipation). For example, stopbands of a rod or plate in an acoustic wave guide could be created and tuned in frequency, by applying high-frequency voltage to periodically distributed imbedded piezoelectric actuators.
The 4D materials and structures to be explored share actuator technologies (e.g. piezoelectric, magneto-/electro-strictive components) with materials and structures that are called smart, intelligent, active, or actuated. However, 4D-materials will not rely on complicated sensing, state estimation, and feedback computation and actuation, but be driven more robustly, by simple feedforward electromagnetic input. General application areas include damping, isolation, and confinement of sound and vibration; acoustic filters and wave guides; wave attenuation and amplification; and synthesis for specified dynamic response.
The project is composed of three sub-projects, fundamental as well as application-oriented: 1) A 4D-rod with Adjustable Bandgaps; 2) Slightly Disordered 4D-Structures for Vibration Confinement; and 3) A 4D-Structure with Local Resonators for Bandgap Lowering.