Additive Manufacturing With Ceramics

The state-of-the-art ceramic armor consists of a heterogeneous boron carbide (B4C) and silicon carbide (SiC) ceramic blend. Uniquely, the combination of these two components can exceed the mechanical performance of each component individually. Traditional ceramic forming techniques includes pressing, extrusion, slip casting, tape casting, and injection molding. These methods are limited in their ability to produce complex shapes, as well as control composition. Additive Manufacturing (AM) allows for rapid prototyping for composite ceramics while controlling the composition.

Army Research Labs previously modified an off-the-shelf 3D printer to print a ceramic slurry of boron carbide and silicon carbide. Using additive manufacturing to produce these ceramic meso/microstructures allows researchers to observe the material properties of different ceramic designs through both layering and mixing of different compositions within layers. Initial iterations suggest improvement in mixedness of the ceramic composite is desirable to create a more homogenous blended microstructure.

The printer consists of three main components: the print head, the feed system, and the gantry. The ceramic slurries are fed into the print head and then extruded out of the nozzle using an augur to mix and convey the slurry down a barrel and out of the print head. The initial design utilized a basic augur shape designed to move the slurry along, but it did not effectively mix the two slurries while printing.

We have recreated this ceramic printer and modified the augur to produce a ceramic print with a more homogenous mixture of the ceramic components. By adding new elements to the augur design, we’ve been able to improve the quality of mixedness of the slurry during the printing process. Mixedness was analyzed for various improved augur designs by creating prints out of colored toothpaste. Toothpaste and the ceramic slurries have similar rheological properties, so it was selected as an appropriate low-cost substitute for the testing process. Measurable color variations were created by printing toothpaste colored with food coloring with plain, white toothpaste.  This allowed for the observation of the impacts of each auger on overall composite mixedness.

Composite mixedness was evaluated for various auger designs to better understand the impact each region of the auger had on the final print and assist with optimization of the final auger design. Once a final auger design was determined, boron carbide and silicon carbide were printed and analyzed to validate the transferability of mixedness from the toothpaste to ceramic composite extrusion.

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