Mechanical response of packings of non-spherical particles: A case study of 2D packings of circulo-lines

We investigate the mechanical response of jammed packings of circulo-lines, interacting via purely repulsive, linear spring forces, as a function of pressure $P$ during athermal, quasistatic isotropic compression. Prior work has shown that the ensemble-averaged shear modulus for jammed disk packings scales as a power-law, $⟨G(P)⟩\sim P^{\beta }$, with $\beta \sim 0.5$, over a wide range of pressure. For packings of circulo-lines, we also find robust power-law scaling of $⟨G(P)⟩$ over the same range of pressure for aspect ratios $\mathcal{R}\gtrsim 1.2$. However, the power-law scaling exponent $\beta \sim 0.8$-$0.9$ is much larger than that for jammed disk packings. To understand the origin of this behavior, we decompose $\langle G\rangle$intoseparatecontributionsfromgeometricalfamilies,$G_f$, and from changes in the interparticle contact network, $G_r$, such that $\langle G \rangle = \langle G_f\rangle + \langle G_r \rangle$. We show that the shear modulus for low-pressure geometrical families for jammed packings of circulo-lines can both increase {\it and} decrease with pressure, whereas the shear modulus for low-pressure geometrical families for jammed disk packings only decreases with pressure. For this reason, the geometrical family contribution $⟨G_f⟩$ is much larger for jammed packings of circulo-lines than for jammed disk packings at finite pressure, causing the increase in the power-law scaling exponent.