Micromechanics-based prediction of thermoelastic properties of high energy materials

High energy materials such as polymer bonded explosives are commonly used as propellants. These particulate composites contain explosive crystals suspended in a rubbery binder. However, the explosive nature of these materials limits the determination of their mechanical properties by experimental means. Therefore micromechanics-based methods for the determination of the effective thermoelastic properties of polymer bonded explosives are investigated in this research. Polymer bonded explosives are two-component particulate composites with high volume fractions of particles (volume fraction $>$ 90%) and high modulus contrast (ratio of Young's modulus of particles to binder of 5,000-10,000). Experimentally determined elastic moduli of one such material, PBX 9501, are used to validate the micromechanics methods examined in this research. The literature on micromechanics is reviewed; rigorous bounds on effective elastic properties and analytical methods for determining effective properties are investigated in the context of PBX 9501. Since detailed numerical simulations of PBXs are computationally expensive, simple numerical homogenization techniques have been sought. Two such techniques explored in this research are the Generalized Method of Cells and the Recursive Cell Method. Effective properties calculated using these methods have been compared with finite element analyses and experimental data.