Study On Mechanical Behavior And Constitutive Model Of Pouring PBX

High speed penetration weapons remain one of the most attractive areas in military research since the idea of precise attack was proposed. Cast polymer bonded explosive (PBX), being used as main charge of penetration warhead, has crucial influence on the stability of penetration and the reliability of detonation of the weapon system. It is necessary to clarify its constitutive behavior under both quasi-static and high loading-rate deformation conditions.In this thesis, the mechanical behaviors and constitutive models of cast PBX under both quasi-static and dynamic conditions are studied. The latest progresses of related research were reviewed at first; then, a cast PBX based on RDX was investigated on its macroscopical properties, mesoscale damage, constitutive models, and anti-acceleration capability, which are summarized as follows:(1) Quasi-static experiments were conducted by a material testing machine, from which stress-strain curves were obtained in the range of10-4～10-2s-1. Further, dynamic experiments were conducted by a split Hopkinson pressure bar setup, which was improved to meet the requirements of stress equilibrium and constant strain rate loading regarding the vicsoelasticity of the cast PBX samples, from which stress-strain information was recorded under high strain-rate up to103s-1.(2) Mechanical behavior of the cast PBX was analyzed. The PBX was found to be a strain-rate sensitive material exibiting non-linear, visoelastic and large-deformation behavior. Elastic modulus, E, compressive strength, σm, and failure strain, εm, are mainly used mechanical parameters, which are linear functions of the logarithmic strain rate in quasi-static experiments. In dynamic testing em also increased with an increasing rate, but σm almost maintained constant.(3) Fracture failure surface of the cast PBX was observed using a scanning electron microscopy (SEM) to indentify its damage mechanism, which was found to mainly be fracture of the binder and debonding of the binder-crystal interface.(4) Constitutive models for one-dimensional compression were then proposed. Non-linear model for quasi-static loading was based on non-linear and damage properties and viso-hyperelastic model for high-rate deformation was on the basis of visco-elastic and hyperelastic theory. The theoretical results predicted by the proposed models show well agreements with experiments data.(5) Finally, actual mechanical response of the material in penetration was simulated via LS-DYNA software, in which the stress and deformation state was discussed in detail.