Dynamic mesoscale damage modeling of polymer bonded explosives with different initial porosity

Polymer bonded explosives (PBXs) are susceptible to the development of structural micro-defects during manufacturing and processing, which degrade their mechanical properties, increase ignition sensitivity, and may even trigger accidental explosions. In this study, the relationships among the mechanical behavior, energy dissipation, pore fractal characterization, damage mechanism, strain rate and initial porosity of samples with different initial porosity were investigated by using Split Hopkinson Pressure Bar. The microstructural features of internal porosity were quantitatively characterized using scanning electron microscopy and Micro-computed tomography. A dynamic mesoscale damage model for PBX was developed, which incorporates initial porosity, tensile failure, shear damage and pore evolution mechanisms. The accuracy of the model was validated by comparing the experimental results with numerical simulations. Based on the established constitutive model, the mechanical behavior, damage distribution and plastic work of PBX samples with different initial porosity under different strain rates were further quantified. The results indicate that the peak pressure of PBX increases with strain rate but decreases with increasing initial porosity. The final damage distribution of the samples follows a pattern where the outer regions of the top and bottom surfaces exhibit higher damage, while the central region shows relatively lower damage.