Guided elastic waves in a highly-stretched soft plate

TL;DR

This study investigates guided elastic wave propagation in a highly-stretched elastomeric plate, revealing anisotropy effects and improving phase velocity predictions by incorporating a rheological model.

Contribution

It introduces an experiment-driven fractional rheological model to accurately predict phase velocities in a highly-stretched elastomer, extending acoustoelastic theory.

Findings

Anisotropy induced by high stretch is characterized by phase velocity measurements.

Standard acoustoelastic theory has limitations in predicting velocities in prestressed elastomers.

A rheological model improves predictions up to 80% elongation.

Abstract

We study the propagation of guided elastic waves in a highly-stretched Ecoflex\c{opyright} plate, a nearly incompressible elastomer. The plate is subjected to a nearly-uniaxial stress with an elongation reaching 120% and we measure in-plane displacements of the shear horizontal mode SH0 and of the plate mode S0 coexisting in the low frequency limit. An induced anisotropy is first observed and characterized by following the phase velocities in two principal directions. Although these measurements provide an initial stress estimate, we evidence the limits of the acoustoelastic theory to predict those phase velocities in a prestressed elastomer. Taking into account the frequency dependent shear modulus of the elastomer, an experiment-driven fractional rheological model is added to the theory. This provides a proper prediction of phase velocities up to 80% elongation.