Some examples of how MacroPac can be used

MacroPac looks at packing particles of different shapes with different size distributions into boxes with various boundary conditions.

and lets you visualize and analyze them . Users can try 'what if' changes with different particles, and gain insights into why their system behaves as it does. Some examples are illustrated here.

(For some older Application Notes, in PDF format, see here. These were produced with earlier versions of MacroPac.)

To see an example of particle segregation when the simulation container is 'shaken', see here.

Decorative Paints

A hard boundary wall on the bottom models the substrate, while the soft boundary at the top represents the interface with air. Periodic boundaries in x and z directions model the extended nature of the coating. Plate-like fillers and spherical pigments are packed into the box. Surface roughness can be seen immediately, as can pigment dispersion. You can use MacroPac's "active classes" facility to see pigment dispersion even more distinctly. By moving particles after they are packed, you can see the effect of settling and film shrinkage.

Short-fibre Reinforced Composites

Hard boundary walls model the walls of an injection mould. The fibres are represented by short rods with a Gaussian distribution of lengths. Local domains of oriented fibres are observed in this 2D simulation, and there is a depletion of fibres near the walls. This can be seen even more clearly using MacroPac's density analysis capability.

Pigment Dispersion in Latex Coatings

The large latex particles are represented by monodisperse spheres. The small pigment particles are forced to aggregate in the space between the latex particles. This is even more apparent if you make the latex particles "inactive" in the visualization. Periodic boundaries have been used in x and z directions in this 3D simulation, since the box represents part of a bulk system. Packing densities of about 60% can be achieved using the settling and shaking options in MacroPac.

Metal Matrix Composites

Fibres are packed into a 3D simulation box, with periodic boundary conditions. The fibres have a log normal size distribution. This visualization corresponds to a packing fraction of only about 7%, and is a snapshot taken while the simulation was running. You can see how adding different particles (for example, spheres) could be used to achieve higher packing fractions. It is also apparent that there can be a big variation in the size of the particles when a log normal distribution is used.

Friction Materials

Carbon is included in many modern brake materials in the form of graphite. Here, platelike graphite has been mixed with two other materials. One is a rubber-like material which is treated as spherical; the other is a cuboid carbon material. Periodic boundary walls have been used in this simulation. Visualization of each component separately is useful in ascertaining how the particles are distributed, which can be important both for the wear (tribological) properties and for thermal dissipation.