<p>The performance of solid rocket
motors (SRMs) is extremely dependent on propellant formulation, operating
pressure, and initial grain geometry. Traditionally, propellant grains are cast
into molds, but it is difficult to remove the grains without damage if the geometry
is too complex. Cracks or voids in propellant can lead to erratic burning that
can break the grain apart and/or potentially overpressurize the motor. Not only
is this dangerous, but the payload could be destroyed or lost. Some geometries
(i.e. internal voids or intricate structures) cannot be cast and there is no
consistent nor economical way to functionally grade grains made of multiple propellant
formulations at fines scales (~ mm) without the risk of delamination between
layers or the use of adhesives, which significantly lower performance. If one
could manufacture grains in such a way, then one would have more control and
flexibility over the design and performance of a SRM. However, new
manufacturing techniques are required to enable innovation of new propellant
grains and new analysis techniques are necessary to understand the driving
forces behind the combustion of non-traditionally manufactured propellant.</p>
<p>Additive manufacturing (AM) has
been used in many industries to enable rapid prototyping and the construction
of complex hierarchal structures. AM of propellant is an emerging research area,
but it is still in its infancy since there are some large challenges to
overcome. Namely, high performance propellant requires a minimum solids loading
in order to combust properly and this translates into mixtures with high
viscosities that are difficult to 3D print. In addition, it is important to be
able to manufacture realistic propellant formulations into grains that do not
deform and can be precisely functionally graded without the presence of defects
from the printing process. The research presented in this dissertation
identifies the effect of a specific AM process called Vibration Assisted
Printing (VAP) on the combustion of propellant, as well as the development of
binders that enable UV-curing to improve the final resolution of 3D printed structures.
In addition, the combustion dynamics of additively manufactured layered
propellant is studied with computational and experimental methods. The work
presented in this dissertation lays the foundation for progress in the
developing research area of additively manufactured energetic materials. </p>
<p>The appendices of this dissertation
presents some additional data that could also be useful for researchers. A more
detailed description of the methods necessary to support the VAP process,
additional viscosity measurements and micro-CT images of propellant, the
combustion of Al/PVDF filament in windowed propellant at pressure, and microexplosions
of propellant with an Al/Zr additive are all provided in this section. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12728123 |
| Date | 28 July 2020 |
| Creators | Monique McClain (9178199) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/ADDITIVE_MANUFACTURING_OF_VISCOUS_MATERIALS_DEVELOPMENT_AND_CHARACTERIZATION_OF_3D_PRINTED_ENERGETIC_STRUCTURES/12728123 |
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