Recovery of the Elastic Constants from Wavespeed Measurements in Viscoelastic Composites by Photoacoustic Technique

Abstract

Mixtures of black rubber (natural rubber) vulcanizates containing various concentrations of sand particles, as hard fillers, were prepared to determine their elastic constants at low and high frequency using the photoacoustic technique. These parameters are related with the degree of sand filler dispersion which determines the changes in stiffness, as well as its potential as reinforcement material for treads in tires. The constants are recovered through measurements of the longitudinal wave and complemented with the predictions from the Kerner model to obtain the Poisson’s ratio. Some results are corroborated with tension and compression tests. The acoustic waves are acquired by two piezoelectric transducers, one centered at 3 kHz and the other at 240 kHz. The results show a slight increase in Young’s modulus at low frequencies; meanwhile at high frequencies, it increases by two orders of magnitude. In addition, we found that on adding small amounts of prepared sand, the stiffness increases and this is particularly convenient to reduce the energy losses by the rolling resistance in automotive vehicles.