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Uhlenhake - Dissertation - Defense - revised 11-23.pdf (6.89 MB)

OPTICAL IGNITION AND COMBUSTION CHARACTERIZATION OF METAL FLUOROPOLYMER COMPOSITES

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posted on 2022-11-28, 20:26 authored by Kyle UhlenhakeKyle Uhlenhake

The ignition of energetic materials, and specifically solid propellants, is a complex process

that must be safe, consistent, and precisely controlled. There is a wide range of applications with

specific ignition requirements for solid propellants including inflation of airbags, propulsion

systems (including rockets), as well as arm and fire devices. Currently, electrical or percussion

pyrotechnic igniters are most the commonly used ignition systems. These systems must be

carefully designed to deliver the proper amount of energy to a specified surface area of the

propellant. A photon light source (i.e. flash or laser-based, ranging from UV to IR wavelengths)

can potentially be used to ignite energetic materials with lower input energy and more precise

spatial and temporal control, thereby improving safety and reliability by eliminating electrical

systems used in pyrotechnic igniters. In addition, they could be potentially safer from stray

electrical charges causing unintentional ignition.

The purpose of this work is to further explore the potential of optical ignition for energetic

systems and identify ideal materials that can be used for optical ignition. In order to identify

optically sensitive materials, we will study ignition energies, ignition delays, flame temperatures,

and other combustion characteristics for possible energetic materials. This research addresses a

gap in understanding of optical ignition for energetic materials, as finding and integrating materials

that are optically sensitive while still being practical can be extremely challenging. These

challenges include: (1) a lack of absorptivity to optical wavelengths in the UV to low-IR range,

and subsequently, a very high sensitivity to input energy at the absorptive wavelengths that makes

sustained ignition difficult, (2) a need for full density materials in practical energetic systems,

while optically sensitive materials are exceedingly difficult to ignite as packing density increases

due to heat transfer, and (3) the lack of research regarding novel fuels/oxidizers for the specific

purpose of optical ignition.

Metal/fluoropolymer energetic materials have been of interest to the energetic materials

community for many years. Due to fluorine’s excellent oxidizing ability, they can be used in

composite materials with metal fuels to produce energetic materials for a wide variety of

applications. Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polycarbon

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monofluoride (PMF), and terpolymers such as tetrafluoroethylene, hexafluoropropylene, and

vinylidene fluoride (THV) have already seen extensive use in applications ranging including

protective coatings, strain gauges, and electronics. However, when combined with metals such as

lithium, magnesium, aluminum, or titanium, they also present an opportunity for a wide variety of

energetic materials. For this study, metal/fluoropolymer composites present a novel opportunity

for exploring optical ignition of widely absorptive, full-density energetic materials. This work will

characterize the combustion and sensitivity of metal/fluoropolymer composites to provide novel

materials for optical ignition of energetics.

Specifically, this work will begin with finding a suitable energetic composite that is optically

sensitive. Once this material has been identified, research will be done to thoroughly characterize

the optically sensitive composite by looking at additive manufacturability, flame temperatures, and

ignition sensitivities from various methods and formulations. Once the material has been

thoroughly characterized, it will be implemented into solid propellants to test the feasibility of the

material in practical energetic systems. Finally, the lessons learned from this work will be applied

to novel formulations to identify new optically sensitive energetic composites.

Funding

Air Force Office of Scientific Research under the Multi-University Research Initiative Grant FA9550-19-1-0008

History

Degree Type

  • Doctor of Philosophy

Department

  • Mechanical Engineering

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Steven Son

Additional Committee Member 2

Christopher Goldenstein

Additional Committee Member 3

Li Qiao

Additional Committee Member 4

Metin Ornek

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