(501a) Bringing Particle Scale Properties into Descriptions of Energetic Powder Behavior Via the Enhanced Centrifuge Technique

Energetic materials powder technology plays a significant role in defense and security applications^1,2. Most solid explosives and propellants are processed at some point in the form of powders. The behavior of such powders is impacted by the behavior of the individual particles which comprise them³, especially their adhesion. While computational models have been developed to predict the behavior of energetic materials and propellants⁴, these cannot accurately account for the effects of particle-scale properties on the behavior of the energetic powder as a whole. In turn, the ability to model and optimize the manufacturing and handling of energetic materials is limited.

This work focuses on developing an experimental and modeling framework that maps particle-scale properties onto experimentally-validated ‘effective’ Hamaker constant distributions that describe van der Waals adhesion forces between particles in powders of energetic material. These distributions represent an engineering approach that allows powders comprised of particles of complex shape and roughness, which are challenging to model, to be described as if they were perfect, smooth spheres, which are comparatively simple to model. The complexity associated with the shape and size distributions of the individual particles is captured by the effective Hamaker constants⁵. This prior work is extended here to measure the adhesion force distribution of explosive powders against different surfaces and to characterize the explosive powder behavior. The resulting size-dependent ‘effective’ Hamaker constant distributions guide the selection of binders, surfaces, and excipient materials used in explosives and propellants.

References

(1) Yu, H. A.; Becker, T.; Nic Daeid, N.; Lewis, S. W. Fundamental Studies of the Adhesion of Explosives to Textile and Non-Textile Surfaces. Forensic Sci. Int. 2017.

(2) Chaffee-Cipich, M. N.; Sturtevant, B. D.; Beaudoin, S. P. Adhesion of Explosives. Anal. Chem. 2013.

(3) Litster, Jim Ennis, Bryan Liu, L. The Science and Engineering of Granulation Processes. 2004.

(4) Walters, D. J.; Luscher, D. J.; Yeager, J. D.; Patterson, B. M. Cohesive Finite Element Modeling of the Delamination of HTPB Binder and HMX Crystals under Tensile Loading. Int. J. Mech. Sci. 2018.

(5) Thomas, M. C.; Beaudoin, S. P. An Enhanced Centrifuge-Based Approach to Powder Characterization: Experimental and Theoretical Determination of a Size-Dependent Effective Hamaker Constant Distribution. Powder Technol. 2017.