This work presents
findings in the combined experimental and computational study of the effects of
anisotropy and microstructure on the behavior of HMX-based energetic materials.
Large single crystal samples of β-HMX were meticulously created by solvent evaporation
for experimental purposes, and respective orientations were identified via
x-ray diffraction. Indentation modulus and hardness values were obtained for
different orientations of β-HMX via nanoindentation experiments. Small-scale
dynamic impact experiments were performed, and a viscoplastic power law model
fit, to describe the anisotropic viscoplastic properties of the crystal. The
anisotropic fracture toughness and surface energy of β-HMX were calculated by studying
indentation-nucleated crack system formations and fitting the corresponding data
to two different models, developed by Lawn and Laugier. It was found that the
{011} and {110} planes had the highest and lowest fracture toughnesses,
respectively. Drop hammer impact tests were performed to investigate effects of
morphology on the impact-induced thermal response of HMX. Finally, the
anisotropic properties obtained in this work were applied in a cohesive finite
element simulation involving the impact of a sample of PBX containing HMX
crystals with varying orientations. Cohesive finite element models were
generated of separate microstructure containing either anisotropic (locally isotropic) or global isotropic
properties of HMX particle. In comparison, the isotropic model appeared to be more deformation resistant.
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/14520003 |
| Date | 30 April 2021 |
| Creators | Ayotomi M Olokun (10730850) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/IMPACT_INDUCED_MICROSTRUCTURAL_AND_CRYSTAL_ANISOTROPY_EFFECTS_ON_THE_PERFORMANCE_OF_HMX_BASED_ENERGETIC_MATERIALS/14520003 |
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