Supershear surface waves reveal prestress and anisotropy of soft materials

TL;DR

This paper investigates supershear surface waves in soft, viscoelastic materials, revealing their properties, effects of prestress and anisotropy, and potential for material characterization.

Contribution

It provides the first combined theoretical and experimental analysis of supershear surface waves in rubbery materials, highlighting their sensitivity to prestress and anisotropy.

Findings

Supershear surface waves can exist in viscoelastic materials regardless of shear quality factor.

Prestress affects supershear wave speed oppositely to Rayleigh waves.

Material anisotropy significantly influences supershear wave behavior.

Abstract

Surface waves play important roles in many fundamental and applied areas from seismic detection to material characterizations. Supershear surface waves with propagation speeds greater than bulk shear waves have recently been reported, but their properties are not well understood. In this Letter, we describe theoretical and experimental results on supershear surface waves in rubbery materials. We find that supershear surface waves can be supported in viscoelastic materials with no restriction on the shear quality factor. Interestingly, the effect of prestress on the speed of the supershear surface wave is opposite to that of the Rayleigh surface wave. Furthermore, anisotropy of material affects the supershear wave much more strongly than the Rayleigh surface wave. We offer heuristic interpretation as well as theoretical verification of our experimental observations. Our work points to the potential applications of supershear waves for characterizing the bulk mechanical properties of soft solid from the free surface.