• Parnell, William J.
• Cotterill, Philip
• Nigro, David

Abstract

The Giant Monopole Resonance is a well-known<br/>phenomenon, employed to tune the dynamic response<br/>of composite materials comprising voids in an elastic<br/>matrix which has a bulk modulus much greater than<br/>its shear modulus, e.g. elastomers. This low-frequency<br/>resonance (e.g. λp/a ≈100 for standard elastomers,<br/>where λp and a are the compressional wavelength<br/>and void radius respectively) has motivated acoustic<br/>material design over many decades, exploiting the<br/>subwavelength regime. Despite this widespread<br/>use, the manner by which the resonance arising<br/>from voids in close proximity is affected by their<br/>interaction is not understood. Here we illustrate<br/>that for planar elastodynamics (circular cylindrical<br/>voids), coupling due to near-field shear significantly<br/>modifies the monopole (compressional) resonant<br/>response. We show that by modifying the number<br/>and configuration of voids in a metacluster, the<br/>directionality, scattering amplitude and resonant<br/>frequency can be tailored and tuned. Perhaps most<br/>notably, metaclusters deliver a lower frequency<br/>resonance than a single void. For example, two<br/>touching voids deliver a reduction in resonant<br/>frequency of almost 16% compared with a single void<br/>of the same volume. Combined with other resonators,<br/>such metaclusters can be used as meta-atoms in<br/>the design of elastic materials with exotic dynamic<br/>material properties.

Topics

• impedance spectroscopy
• composite
• void
• bulk modulus
• elastomer