Energy localization and heat generation in composite energetic systems under high-frequency mechanical excitation

Mares Jr., Jesus O. PhD, Purdue University, December 2016. Energy Localization and Heat Generation in Composite Energetic Systems under High-Frequency Mechanical Excitation. Major Professor: Steven F. Son, School of Aeronautics and Astronautics. The ability of high-frequency mechanical excitation to induce heat within select composite explosives may be used to enhance the detectability of such targets due to the associated increase of detectable vapors of the energetic materials. Additionally, the investigation of such heating within these systems in response to the high strain-rate mechanical excitation may improve the understanding of the formation and growth of “hot spots”, or localized regions of intense heating, commonly understood as the fundamental driving mechanism of the initiation of detonation in explosives. In this work, the ability to use high frequency mechanical excitation to generate significant heating within plastic bonded explosives, as well as single energetic particles embedded within a viscoelastic binder, is studied. In this work, the fundamental mechanisms associated with the conversion of high-frequency mechanical excitation to heat as applied to these composite energetic systems are thoroughly investigated. High-frequency contact excitation has been used to generate a significant amount of heat within samples of PBX 9501 and representative inert mock materials. Surface temperature rises on the order of 10 °C were observed at certain frequencies over a range from 50 kHz to 40 MHz at thermal steady state conditions. The mechanical responses of these samples were also measured to explore the connection between the thermal and bulk motion of the samples. It was found that significant heating of the samples near the