On‐The‐Fly Mixing and 3D Printing of Al/CuO Thermite for Controlling Reactivity

摘要

The ability to spatially control the behavior of reactive materials within a part is now a reality withadvances in 3D printing. This vastly opens up the design space for rapidly deflagrating materials, such aspyrotechnics or thermites, to yield a precise property or dynamic performance. In order achieve this goal,a mixing print head was used to mix an aluminum and a copper oxide ink on the fly. The mixing and printingparameters were first investigated for a stoichiometric mix of fuel and oxidizer to determine at what pointthe material can be assumed well‐mixed. The equivalence ratio was then changed, and the critical mixingparameters established. The reactivity was characterized by printing a strip of material, then initiating thethermite and measuring the propagation velocity with a high‐speed camera. Once the velocity reached aplateau, we considered the system well mixed. 3D printing was then used to make parts where the localstoichiometry, which corresponds to performance, is spatially varied. Collective effects of havingincorporated features with differing reactivities were investigated.