On the Thermomechanical Response of HTPB Composite Beams Under Near-Resonant Base Excitation

Currently, there is a pressing need to detect and identify explosive materials in both military and civilian settings. While these energetic materials vary widely in both form and composition, many traditional explosives consist of a polymeric binder material with embedded energetic crystals. Interestingly, many polymers exhibit considerable self-heating when subjected to harmonic loading, and the vapor pressures of many explosives exhibit a strong dependence on temperature. In light of these facts, thermomechanics represent an intriguing pathway for the stand-off detection of explosives, as the thermal signatures attributable to motion-induced heating may allow target energetic materials to be distinguished from their more innocuous counterparts. In the present work, the mechanical response of a polymeric particulate composite beam subjected to near-resonant base excitation is modeled using Euler-Bernoulli beam theory. Significant sources of heat generation are identified and used with distributed thermal models to characterize the system’s thermomechanical response. In addition, the results of experiments conducted using a hydroxyl-terminated polybutadiene (HTPB) beam with embedded ammonium chloride (NH₄Cl) crystals are presented. The thermal and mechanical responses of the sample are recorded using infrared thermography and scanning laser Doppler vibrometry, and subsequently compared to the work’s analytical findings. By adopting the combined research approach utilized herein, the authors seek to build upon recent work and bridge the considerable gap that exists between theory and experiments in this specific field. To this end, the authors hope that this work will represent an integral step in enhancing the ability to successfully detect explosive materials.