Characterization of the Viscous Behavior of Compacted Ceramic Particles Under Shear and Pressure Loads

Ceramic armors are known to provide excellent ballistic resistance, but the precise mechanisms of projectile defeat in these systems are not fully understood. A critical stage in the penetration process is the flow of the pulverized ceramic past the projectile. To further understand this phenomenon, we are investigating the flow and energy dissipation of granular beds, specifically under conditions of high pressure. Two different viscometer systems are designed and fabricated to characterize the behavior of ceramic particles under shear stress and high pressures. The first system is a Couette flow device with ability to exert pressure on the particles during its rotation and measure the torque and angular velocity of the system. These data are used to extract viscosity and energy dissipation due to friction between particles as a function of the shear rate. The second system focuses on the movement of a cylinder through a bed of compacted ceramic particles. By measuring the force required to move the cylinder through the compacted bed, we can evaluate the effective resistance of the particle bed under various compaction pressures. By characterizing the friction coefficient, we obtain the apparent viscosity of the compacted granules under different pressure loads for low strain rates. This characterization should prove useful in understanding the shearing and dissipation mechanisms between granular particles under high pressures.