Shape and size effects on the packing density of binary spherocylinders

The shape and size of particles are the main factors which influence the packing density of binary mixtures. However, investigations of the single effect of size and shape on the binary mixtures of non-spherical particles are much absent. A systematic computational investigation on the binary packing of spherocylinders considering the single effect of shape and size respectively is carried out with the sphere assembly models and relaxation algorithm. Random packings of binary spherocylinders with the same volume, aspect ratio and diameter are simulated numerically to investigate the single effect of shape, size and their combination respectively. The shape effect is observed to present a linear relationship between the packing density and the volume fraction, while the size effect shows a trend of convex. The combined effect, as the case of the same diameter, can be considered as a linear superposition of the shape and size effect, since we find the particle size and shape determine the mixture density independently with no coupling terms. Accordingly, we propose an explicit empirical formula for evaluating the mixture density of binary spherocylinders, and the predicted densities agree well with the simulation results and previous empirical formula in all the cases of the same volume, aspect ratio and diameter, as well as some general cases. For verification, the monophasic packings of spherocylinders are simulated and the results coincide with previous works.