Transient Thermo-mechanics of Carbon Nanotube-enhanced Simulant Explosives
Modern polymer bonded explosives (PBXs) are often characterized by a sensitive response toexternal thermo-mechanical insult that in some cases can lead to accidental detonation. Temperature localizations, "hot-spots", generated via thermo-mechanical insults on PBXs and their inert analogs, polymer-bonded simulants (PBS), have been a source of extensive research in materials engineering. A possible method for desensitizing PBXs without deleterious performance effects is the multi-functional tailoring of mechanical properties through the incorporation of multi-walled carbon nanotubes (MWCNTs) in the polymer binder phase. Here a fabrication method is presented that produces polymer bonded simulants (PBS) of PBX that incorporate MWCNTs into the binder phase, hydroxyl-terminated polybutadiene (HTPB). These materials were characterized via unconfined quasi-static uniaxial stress compression testing. Additionally, this work characterizes the formation and diffusion of temperature localizations under low-velocity drop-weight impact through in-situ thermography. The transport properties of these enhanced-PBS materials are characterized via thermal conductivity and thermal diffusivity measurements. These nano-inclusions significantly modified the bulk transport and mechanical properties of the material. Under the micrometer length scale and millisecond time scale conditions the enhanced transport properties in the PBS test articles exhibited a significant attenuation in temperature localization magnitude, duration, and amount. Quasi-static compression showed evidence of a MWCNT induced structural skeleton effect that provided the binder with an increased strength, load transfer, and a greater ability to resist strain localizations prior to failure. These results have significant implications for MWCNTs in the synthesis of a multi-functional material that can desensitize energetic materials without diminishing their performance.