Visco-hyperelastic constitutive modeling of the dynamic mechanical behavior of HTPB casting explosive and its polymer binder

A new visco-hyperelastic constitutive model is developed to describe the dynamic compressive behavior of polymer-bonded explosive (60 wt% RDX, 16 wt% aluminum, and 24 wt% HTPB) and its polymer binder. The constitutive relationship comprises two parts: a component with a strain-energy function to characterize large deformation and a viscoelastic model to describe dynamic viscoelastic behavior. The hyperelastic model parameters are curve-fitted using quasi-static compressive test data under a strain rate of 0.0001s-1. The time–temperature superposition principle master modulus curves are studied using relaxation tests at different temperatures, and their compressive relaxation time and modules are obtained by fitting the master modulus curves. To obtain the rational dynamic compressive results, a modified split-Hopkinson compressive bar setup is designed such that the specimens are in dynamic stress equilibrium and deformed homogeneously at nearly constant strain rates. A comparison of the constitutive relationship with the experimental results revealed a good agreement and demonstrates its potential to describe the dynamic mechanical behavior of the PBX and its polymer binder.