Additive Manufacturing of Energetics: from propellants to initiator inks

Additive manufacturing (AM) has become an ever-increasing field of research offering advantages in accuracy, logistics, and design that are difficult or impossible through conventional manufacturing methods. Adaptation of additive manufacturing techniques for energetic materials, whether it is nitrocellulose-based munition propellant, rocket propellant with solids loading greater than 85%, or high explosives, has lagged behind most other materials in being adapted to AM methods. In this talk, an overview of two additive manufacturing projects in Dr. Hargather’s lab are given. First, characterization of metallized solid rocket propellant for use in an additive-manufacturing platform was performed on a customized print platform by measuring viscosity and material slump. Material suitable for additive-manufacture in varying environments must be capable of creating self-supporting structures with smooth bonding to avoid large numbers of interstitial voids. It was found that compositions around 87.5% solids had the ability to self-support after extrusion while maintaining a high but usable viscosity. Second, ongoing work on the development and characterization of a pyrotechnic initiator ink is presented. The goal of the initiator ink is to demonstrate multi-point initiation on an energetic substrate. Formulation development and initial characterization of the viscosity and burn rates of thermites blended with iron sulfide in an energetic binder are discussed.