| Thermomechanical modeling of energetic materials, for example solid rocket motor propellants and explosives, is a complex problem due to the large number of behaviors such a material may exhibit. Experiments have shown that these materials are nonlinearly viscoelastic, and may also experience plastic flow (permanent deformation), phase changes (melting and vaporization processes), and combustion. In addition, these phenomena are often strongly coupled, making modeling very difficult. Compounding the difficulty further, reliable experimental data on the properties of these types of materials are quite scarce.; Applying advanced tools of continuum thermomechanics, we have developed a fully three-dimensional framework which, in the most general form, is able to model all the mentioned behaviors of energetic materials. The concept of a balance of microforces, forces which drive changes in material microstructure, is employed to generate thermomechanically consistent equations of evolution for combustion and phase transitions.; The model is then simplified to a set of three model problems: the constant-volume thermal explosion, one-dimensional shear loading, and one dimensional longitudinal loading. These model problems were solved numerically using essentially non-oscillatory and total variation diminishing methods. The solutions reveal extremely rich behavior, including complex wave phenomena, strain localization phenomena, and changes of material phase. |
