<p>  </p> <p>The additive manufacturing of energetic materials is a novel way to alter the properties of an energetic material without necessarily changing its chemical structure. There are many methods of additive manufacturing which can be applied to energetic material fabrication, each of which have unique advantages and disadvantages. The most well characterized additive manufacturing method is the commercially refined technique of fused filament fabrication (FFF) printing. FFF manufacturing techniques can be applied to additively manufacture thermoplastic energetic materials. The thermoplastic aluminum and polyvinylidene difluoride (Al/PVDF) system is suitable for manufacture with FFF techniques, shapeable into pyrotechnics with custom geometries using commonly available FFF printers. This theoretically allows Al/PVDF systems to be tailored for a wide variety of multifunctional needs, such as reactive structures. Following a literature review describing energetic material additive manufacturing techniques, this thesis focuses on the creation of outwardly identical Al/PVDF samples and the use of a geometric correction factor to control for uneven feedstock diameter. By varying the infill pattern, infill density, and interior geometry, different sample energy densities were obtained and observed during combustion. High speed videography measurements and the mass of individual samples were used to estimate the overall energy release rate. An Ashby plot contrasting the energy density and energy release rate was obtained. While full density printed samples burned similar to cast propellant strands in a linear burn, the energy release rates of additively manufactured Al/PVDF could be increased via convective combustion by varying the infill type and density. These results have significance for the fields of structural energetic materials and for additive manufacturing studies of energetic materials.</p>

<div>The work discussed in this document seeks to integrate conductive additives with energetic material systems to offer an alternative source of ignition for the energetic material. By utilizing the conductive properties of the additives, ohmic heating may serve as a method for preheating and igniting an energetic material. This would allow for controlled ignition of the energetic material without the use of a traditional ignition source, and could also result in easier system fabrication.</div><div>For ohmic heating to be a viable method of preheating or igniting these conductive energetic materials, there cannot be significant impact on the energetic properties of the energetic materials. Various mass solids loadings of graphene nanoplatelets (GNPs) were mixed with a reactive mixture of aluminum (Al)/polyvinylidene fluoride (PVDF) to test if ohmic heating ignition was feasible and to inspect the impact that these loadings had on the energetic properties of the Al/PVDF. Results showed that while ohmic heating was a plausible method for igniting the conductive energetic samples, the addition of GNPs degraded the energetic properties of the Al/PVDF. The severity of this degradation was minimized at lower solids loadings of GNPs, but this consequently resulted in larger voltage input requirements to ignite the conductive energetic material. This was attributable to the decreased conductivities of the samples at lower solids loading of GNPs.</div><div>In hopes of conserving the energetic properties of the Al/PVDF while integrating the conductive additives, additive manufacturing techniques, more specifically fused filament fabrication, was used to print two distinct materials, Al/PVDF and a conductive composite, into singular parts. A CraftBot 3 was used to selectively deposit Conductive Graphene PLA (Black Magic) filament with a reactive filament comprised of a PVDF binder with 20% mass solids loadings of aluminum. Various amounts of voltage were applied to these conductive energetic samples to quantify the time to ignition of the Al/PVDF as the applied voltage increased. A negative correlation was discovered between the applied voltage and time to ignition. This result was imperative for demonstrating that the reaction rate could be influenced with the application of higher applied voltages.</div><div>Fused filament fabrication was also used to demonstrate the scalability of the dual printed conductive energetic materials. A flexural test specimen made of the Al/PVDF was printed with an embedded strain gauge made of the Black Magic filament. This printed strain gauge was tested for dual purposes: as an igniter and as a strain sensor, demonstrating the multi-functional use of integrating conductive additives with energetic materials.</div><div>In all, the experiments in this document lay a foundation for utilizing conductive additives with energetic materials to offer an alternative form of ignition. Going forward, ohmic heating ignition may serve as a replacement to current, outdated methods of ignition for heat sensitive energetic materials.</div>