Modelling Microstructural Deformation and the Failure Process of Plastic Bonded Explosives Using the Cohesive Zone...

Area of Science:

• Materials Science
• Computational Mechanics
• Energetic Materials

Background:

• Polymer-bonded explosives (PBX) require detailed understanding of their mechanical behavior for safe handling and performance.
• The complex microstructure of PBX 9501, comprising Cyclotetramethylene tetranitramine (HMX) particles in a polymeric binder, significantly influences its mechanical response.
• Existing models may not fully capture the interplay between microstructure and failure mechanisms under various loading conditions.

Purpose of the Study:

• To develop and validate a microstructure finite element model for simulating the mechanical behavior, deformation, and failure of PBX 9501.
• To investigate the primary failure mechanisms of PBX 9501 under tensile and compressive quasi-static loading.
• To evaluate the influence of interface properties and strain rates on the macroscopic performance of PBX 9501.

Main Methods:

• A finite element method incorporating a cohesive zone model (CZM) was employed.
• PBX 9501 microstructure was modeled with elastic HMX particles and a viscoelastic binder.
• Cohesive elements with bilinear softening were integrated at interfaces and within material components to simulate debonding and fracture.

Main Results:

• Macroscopic stress-strain curves from the model showed good agreement with experimental data under tension and compression across different strain rates.
• Interface debonding perpendicular to the loading direction was identified as the primary tensile failure mode.
• Under compression, shear failure at interfaces and HMX particle fracture were significant contributors to overall failure.

Conclusions:

• The developed CZM-enhanced finite element model accurately predicts the macroscopic mechanical responses of PBX 9501.
• The study elucidates the distinct failure mechanisms governing tensile and compressive loading in PBX 9501.
• Understanding the relationship between microstructure, interface properties, strain rate, and mechanical behavior is crucial for PBX 9501 performance prediction.