Elastic waves in particulate glass-rubber mixture: experimental and numerical investigations/studies

Abstract

In this paper we study by wave propagation the elastic response of granular mixtures made of soft and stiff particles subjected under hydrostatic pressure/stress. This allows inferring fundamental properties of granular materials such as elastic moduli and dissipation mechanisms. We compare physical experiments in a triaxial cell equipped with piezoelectric wave transducers and Discrete Element Method simulations (DEM). In the experimental part, dense, static packings made of monodisperse glass and rubber beads are prepared at various levels of hydrostatic stress and species fractions. Small perturbations are generated on one side and the time of flight through the glass-rubber mixtures are measured to quantify the effect of the mixture composition on the elastic moduli. Interestingly, the experiments show that the behavior is non-linear and nonmonotonic with increasing percentage of rubber particles. Wave velocity and modulus remain fairly constant when increasing the fraction of rubber to 30%, while they experience a sudden drop between 30% and 60%, to become again constant between 60% to 100%. DEM simulations offer deeper insights into the micromechanics in and at the transition between the glass-and rubber-dominated regimes. The simplest analysis with Hertzian spherical particles of different stiffness is performed as a preliminary step. The behavior of mixtures with high glass content is very well captured by the simulations, without need of any additional calibration, whereas the complex interaction between rubber and glass leave open questions for further study.

Micromechanics of complex granular materials: a focus on small strain behavior

“…To address this topic, we have performed wave-propagation experiments on isotropic mixtures particles of two different species, namely glass and rubber beads, but identical size. Details of the experiments are reported in [18]. Results are consistent with evidences by previous studies [6,11] and show how granular mixtures can be engineered to exhibit exceptional properties.…”

Elastic waves in particulate glass-rubber mixtures

“…In this study, we apply ultrasound through transmission techniques in order to study stiffness and attenuation in granular materials made of mixtures of glass and rubber beads. The focus is on the effect of the volumetrical composition of the mixture and the stress level, where these factors can be exploited to optimize the material stiffness and density [15]. In addition, granular media show intrinsically high attenuation.…”

Elasticity and Wave Propagation in Granular Materials

“…A similar behavior was observed more recently in Ref. [236] for longitudinal waves in binary mixtures of glass and rubber beads of equal diameter.…”

“…Various authors have compared the predicted values of the effective bulk and shear moduli of granular assemblies with the results of DEM simulations [2,105,116,159,229] and physical experiments [94,159,160,236]. It has been shown that a proper description of the microstructure, as related to both particle characteristics and load history, is essential for the characterization of granular elasticity [155,233].…”

“…Despite the fact that DEM is a very efficient tool to study these applications, modeling of confined high to extreme compression with DEM is still a challenge. In classical DEM, the so-called soft particle approach [151,236], particle deformations mimicked by overlaps between contacting particles. When an overlap is detected, the contact forces between two particles are calculated by a contact law.…”