Pressure-dependent shear modulus of jammed packings of non-spherical particles

There have been numerous studies of the structural and mechanical properties of jammed packings of spherical particles, yet there have been far fewer studies of jammed packings of non-spherical particles. Here, we generate jammed packings of circulo-lines in two spatial dimensions (2D) and study their mechanical response. Previously, we showed that the shear modulus of jammed disk packings decreases linearly with pressure, p, within geometric families, G_f = G₀ – A p, where the contact network of the packing does not change. In contrast, the ensemble-averaged shear modulus increases as <G> » G₀ + B p^a, where a» 0.5 for jammed packings of spherical particles, due to particle rearrangements. For jammed packings of circulo-lines, we find that the shear modulus of geometrical families can increase, as well as decrease with pressure: G_f = G₀ ± A’ p. We show that the increase of G_f with pressure is related to local shear-induced dilation for particles with rotational degrees of freedom. We find that the ensemble-averaged shear modulus <G> - G₀ » p^a for packings of circulo-lines scales as a power-law with pressure, but a»0.8, which is larger than the value for packings of spherical particles.