Mechanical properties of β-HMX

Area of Science:

• Materials Science
• Crystallography
• Solid Mechanics

Background:

• Understanding material mechanical properties requires knowledge of defect structures.
• Microhardness indentation is a valuable technique for this investigation.

Purpose of the Study:

• To investigate the mechanical properties and defect structures of HMX using microhardness indentation.
• To identify preferred slip planes and dislocation glide mechanisms in HMX.

Main Methods:

• Microhardness indentation (Vickers and Knoop) on various HMX faces.
• Etching of indented surfaces to reveal slip planes.
• Tensile testing to observe deformation behaviors like twinning.

Main Results:

• Vickers hardness: 304-363 MPa; Knoop hardness: 314-482 MPa.
• Identified preferred slip planes as (001) and (101) with specific dislocation glide configurations.
• Observed primary twinning at 2.3 MPa stress during tensile testing, with a twinning shear strain of 0.353.

Conclusions:

• HMX exhibits brittle behavior, comparable to other organic solids.
• Dislocation slip significantly accommodates local deformation stresses under indentation.
• Identified slip systems provide insights into HMX's mechanical response.