A Method for the Determination of the Viscoelastic Relaxation Modules of PBX by Confined SHPB Measurements

Abstract

Polymer bonded high explosives (PBX) show viscoelastic material behaviour due to the polymeric binder material. The assessment of safety aspects in the use of PBX requires a profound understanding of the dynamical mechanical behaviour for short loading times. The work presents an experimental set up with split Hopkinson pressure bar techniques (SHPB) that uses a confined material sample for highly dynamical loading conditions. The test method allows the experimental determination of the complete stress-strain-state in the dynamically loaded sample. The SHPB results provide the input data for the developed viscoelastic material description. The material model is based on the Boltzmann superposition principle and requires 2 time dependent relaxation functions for a complete viscoelastic material description. In our case this are the relaxation functions for compression K(t) and shear G(t). A method is presented for the solution of the developed integral equations for these two relaxation functions. The mathematical method is verified with generic viscoelastic models and is finally applied for the characterisation of the PBX KS-32.