Elastic waves in particulate glass-rubber mixtures

Area of Science:

• Materials Science
• Physics
• Acoustics

Background:

• Granular materials exhibit complex mechanical behaviors under stress.
• Understanding wave propagation is key to characterizing elastic properties.
• The influence of soft inclusions on granular packings is not fully understood.

Purpose of the Study:

• To investigate wave propagation in granular packings with varying soft (rubber) and stiff particle content.
• To determine the effect of hydrostatic stress and rubber content on elastic properties.
• To analyze the transition between glass- and rubber-dominated regimes and energy dissipation.

Main Methods:

• Physical experiments using a triaxial cell.
• Ultrasound wave propagation measurements at high frequencies.
• Time-of-flight and spectral analysis to deduce elastic properties and damping.

Main Results:

• Bulk stiffness is nonlinear and non-monotonic with increasing rubber content, especially at higher pressures.
• Spectral analysis reveals a transition from a glass- to a rubber-dominated regime.
• Mixtures with <30% rubber content exhibit enhanced damping and slightly increased stiffness.

Conclusions:

• Rubber particle content significantly influences the elastic and damping properties of granular packings.
• Hydrostatic stress plays a crucial role in the observed nonlinear behavior.
• A transition in material behavior is observed with increasing rubber content, impacting energy dissipation.