(380c) Solids Metrics for Successful 3D Printing of Energetic Feedstocks

Traditional manufacturing methods for producing warheads, propellants, and pyrotechnic systems are timely and costly. Additive manufacturing (AM) approaches offer one path of alternative manufacturing technologies. Among various technologies, powder bed fusion (PBF) is one promising approach. A PBF printer is essentially a miniature manufacturing facility in a box, with significant powder handling challenges that must be overcome for robust production performance and part quality [1, 2]. Feedstock handling in a powder bed fusion printer is no different than and faces the same challenges as full-scale solids handling processes.

For a feedstock to function properly in a powder bed fusion 3D printer, it must be designed to meet several material characteristics. Some of the most important material properties include: powder flowability & cohesion, powder and roll friction, permeability, particle size & shape distribution (PSSD), triboelectric charging propensity, wetting characteristics, compaction characteristics and thermal softening point.

This paper presents select studies of developing feedstocks for PBF printing of energetic and other materials. Key attributes benchmarked against included powder flowability, aeration attributes, wetting behavior, spreadability, and fusion, as well as final part performance (bulk density, detonation, sensitivity, and part tolerances.)

[1] Ennis, B.J. et al. (2008) Section 21: Solids-Solids Operations & Processing. Perry’s Chemical Engineers’ Handbook. Perry, R. H., & Green, D. W. (eds.), New York: McGraw-Hill.

[2] Ennis, B.J. et al. (2017), HPC4Mfg Modeling of Powder Dynamics in Metal Additive Manufacturing, Austin, TX. Link for presentation:

https://hpc4mfg.llnl.gov/pdfs/events/powder2017/Powder_Dynamics_EG_17oct...

[3] Ennis, B.J. et al. (2017). Navy SBIR Phase I and Phase II Awards. Development of Explosive Feedstock for Commercial-off-the-Shelf (COTS) 3D Printers. Link for award:

https://www.navysbirprogram.com/NavySearch/Award/award.aspx?pk=869CC83B-5945-4E75-A598-AA2527D51045

[4] "Chattanooga firm to help U.S. Navy figure out how to 3-D print explosives" (2017), T. Omarzu,

Chattanooga Times Free Press. Story link:

http://www.timesfreepress.com/news/business/aroundregion/story/2017/dec/10/chattanoogfirm-help-us-navy-figure-out-how-3-/458777/