(85b) Effect of Size and Mechanical Properties of Particles on the Microstructure and Tensile Strength of Compacted Powders

Compaction is one of the most common industrial processes used to achieve densification of powders and to develop tensile strength or resistance to crushing. Several factors, including powder properties, applied compaction pressure, and the shape of tooling affect the compaction process itself and the final outcome. Even though several prior studies have addressed this topic in detail, the compaction process is still not well understood, particularly in terms of developing a mechanistic relationship between particle scale (micro scale) properties and the powder compact (macro scale) properties such as relative density and tensile strength. In order to understand the effect of particle properties, such as particle size, plasticity, elasticity, and surface bonding energy, on the powder compact, we ran several experiments and discrete particle simulations. We studied lactose and microcrystalline cellulose powders, which are one of the most commonly used excipients in pharmaceutical industry, and also metallic powders. The exact particle size distributions of these powders are represented in the simulations, and the mechanical properties of the particles are calibrated using the powder compaction experiment results. Then, we validated our simulation results based on experimental indirect tensile strength test. We found that the simulation results are quantitatively similar to experimental results. Once the simulations are validated, we used the simulations to investigate the microstructure evolution during the compaction process, particularly that of the size and the mechanical properties of the particles. The evolution of the microstructure is studied by analyzing the evolution of the magnitude, orientaiton, and spatial and temporal distribution of the contact forces and the bonding forces between the particles. In this presentation, we will discuss the experimental and simulation methods and results in detail.