Abstract
For energetic crystals such as HMX, the sensitivity of the material to shock, the possibility of initiation, and the subsequent reaction is known to be controlled by processes occurring at the crystal level. The anisotropic nature of β-HMX can be critical in determining the performance of HMX based polymer bonded explosives, which are widely used across multiple industries as propellant or explosives. In this work, we experimentally obtain constitutive parameters for characterizing the response of multiple crystalline planes of β-HMX crystals to external loading. Nanoindentation and small-scale dynamic impact experiments were performed on multiple planes of β-HMX crystals to comparatively measure the indentation moduli in multiple orientation directions. Anisotropic material behavior, involving constitutive elastic and non-elastic parameters, was measured and studied. Findings regarding material properties for the (100), (010), (001), {110}, and {011} planes of β-HMX are presented and compared with literature data.
Highlights
Accurate characterization and prediction of the mechanical behavior of energetic materials (EMs) requires indepth understanding of their physical properties and of their response to external stimuli
The indentation modulus corresponding to the directional elastic modulus, E11, were obtained by loading along a direction determined by the cross product between the a and c crystallographic axes
Indentation modulus and hardness values were obtained for each plane via nanoindentation experiments
Summary
Accurate characterization and prediction of the mechanical behavior of energetic materials (EMs) requires indepth understanding of their physical properties and of their response to external stimuli. For an energetic material such as HMX, sensitivity to shock, the possibility of initiation, and the subsequent reaction is known to be controlled by processes occurring at the crystal level. Thermal stability of the β-HMX crystalline phase makes it a good candidate to characterize effect of anisotropy on HMX material behavior. Previous experiments have pointed to the anisotropic nature of β-HMX being critical in determining the performance of HMX based polymer bonded explosives (PBX) [3]. With respect to particle fracture, due to the anisotropic nature of HMX, it is known that deformation in single crystals of β-HMX is orientation dependent and fracture tends to occur along cleavage planes. Indentation experiments performed by Palmer and Field [5] on cleaved crystals determined the
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