Characterization and Micromechanical Modelling of a Temperature Dependent Hyper-viscoelastic Polymer Bonded Explosive

Technical paper presented at the 2017 Defence and Security Doctoral Symposium.

Polymer bonded explosives (PBXs) are highly filled binary particulate composites, typically >90% volume fraction. The composites consist of a compliant matrix binder and rigid filler crystals. In order to predict the bulk composite behaviour, the polymer matrix material properties and a suitable constitutive model was determined for use in a multi-scale micromechanical finite element model.

The matrix material was characterized using monotonic tensile tests at room temperature as well as small strain and large strain shear rheometric tests at different temperatures. A temperature-dependent visco-hyperelastic constitutive model combining the use of the Prony series and the Van der Waals potential was used to describe the matrix material behaviour. Material parameters at room temperature were first optimized by minimisation of the error function between the experimental and predicted behaviour (MATLAB, MathWorks). Temperature dependence for higher temperatures was then determined using time-temperature superposition.

A 3D micromechanical finite element model, reconstructed from X-Ray tomographic data, was used for prediction of the composite fracture behaviour. Due to the loss of the smaller filler particles during image processing, a multi-scale hierarchical model was developed to incorporate the missing volume fraction.