Cohesive granular materials composed of nonconvex particles

Area of Science:

• Physics
• Materials Science
• Engineering Mechanics

Background:

• Macroscopic cohesion in granular materials is crucial for their mechanical behavior.
• The influence of particle shape, particularly nonconvexity, on cohesion is not fully understood.
• Sticky particles introduce complexities in modeling granular material interactions.

Purpose of the Study:

• To investigate the relationship between particle shape and macroscopic cohesion in granular materials.
• To quantify the effect of nonconvexity on the mechanical response of sticky granular packings.
• To analyze the role of strain and stress inhomogeneities in determining material cohesion.

Main Methods:

• Contact dynamics simulations were employed to model 2D packings of sticky, nonconvex aggregates.
• Simulations involved unconfined axial compression and shearing of the granular materials.
• Analysis focused on macroscopic cohesion, strain/stress distributions, and contact network evolution.

Main Results:

• Macroscopic cohesion strongly depends on internal strain and stress inhomogeneities.
• Cohesion increases linearly with the degree of particle nonconvexity under axial compression.
• Sheared packings show increased contacts with fewer neighbors as nonconvexity rises.
• Shearing results in either isotropic tensile contacts or a privileged direction for compressive contacts.

Conclusions:

• Particle shape, specifically nonconvexity, is a key determinant of macroscopic cohesion in sticky granular materials.
• The development of internal stress and strain heterogeneities significantly modulates cohesion.
• Understanding these shape-dependent behaviors is critical for predicting granular material performance in engineering applications.