<p>Thermal dissipation of mechanical energy
from periodic loading in energetic materials (EMs) leads to the creation of areas
of intense, localized heating, called hot spots. The impact and shock conditions
for the hot spot initiation of solid explosives have been extensively explored,
but little work has focused on high-frequency contact loading. In order to
design formulations to address unintentional initiation by mitigating heating
in polymer-bonded explosives (PBXs) and other heterogeneous EMs, the mechanisms
of heat generation which lead to the thermal initiation of energetic composites
under ultrasonic excitation were explored. Heat generation mechanisms which may
lead to unintentional initiation were identified through the diagnostic
techniques of second harmonic generation (SHG) of δ-HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine)
crystals; X-ray phase contrast imaging (PCI) performed at the Argonne National
Laboratory Advanced Photon Source; infrared (IR) thermography; and optical
microscopy. This work concludes with high-speed mesoscale observations of dense
layers of PETN (pentaerythritol tetraniterate), CL-20
(hexanitrohexaazaisowurtzitane), RDX (1,3,5-trinitro-1,3,5-triazine), and HMX which
were damaged or driven to decomposition under acoustic insult using the non-intrusive
imaging technique of shadowgraphy to detect hot spots within the transparent
binder. Recommendations are formed which address binder adhesion, energetic
material properties, and particle morphology on the vibration sensitivity of a
PBX formulation. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8966264 |
| Date | 15 August 2019 |
| Creators | Zane A Roberts (6998114) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Heat_Generation_Mechanisms_in_Energetic_Composite_Materials_Under_Ultrasonic_Excitation/8966264 |
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