Compression-driven jamming in porous cohesive aggregates

TL;DR

This study explores how porous, cohesive, frictionless disk aggregates transition into a jammed state under compression, revealing the influence of initial structure on jamming behavior and elastic properties.

Contribution

It provides new insights into the dependence of jamming transition and elastic response on aggregate morphology and initial packing procedures.

Findings

Jamming transition occurs at specific packing fractions for different aggregate types.

Pressure near jamming follows a quadratic relation with packing fraction difference.

Elastic response resembles that of random spring networks.

Abstract

I investigate the compression-driven jamming behavior of two-dimensional porous aggregates composed of cohesive, frictionless disks. Three types of initial aggregates are prepared using different aggregation procedures, namely, reaction-limited aggregation (RLA), ballistic particle-cluster aggregation (BPCA), and diffusion-limited aggregation (DLA), to elucidate the influence of aggregate morphology. Using distinct-element-method simulations with a shrinking circular boundary, I numerically obtain the pressure as a function of the packing fraction $\phi$. For the densest RLA and the intermediate BPCA aggregates, a clear jamming transition is observed at a critical packing fraction $\phi_{\rm J}$, below which the pressure vanishes and above which a finite pressure emerges; the transition is less distinct for the most porous DLA aggregates. The jamming threshold depends on the initial structure and, when extrapolated to infinite system size, approaches $\phi_{\rm J} = 0.765 \pm 0.004$ for RLA, $0.727 \pm 0.004$ for BPCA, and $0.602 \pm 0.023$ for DLA, where the errors denote the standard error. Above $\phi_{\rm J}$, the pressure follows $P \approx A {( \phi - \phi_{\rm J} )}^{2}$, which implies that the bulk modulus $K$ of jammed aggregates is proportional to $\phi - \phi_{\rm J}$. Rigid-cluster analysis of jammed aggregates shows that the average coordination number within the largest rigid cluster increases linearly with $\phi - \phi_{\rm J}$. Taken together, these relations suggest that the elastic response of compressed porous aggregates is analogous to that of random spring networks.