Study Of Dynamic Mechanical Property And Impact Damage Behavior Of PBX

Polymer bonded explosives(PBXs)have usually been considered as a particulate composite material containing the energetic grains embedded in a viscoelastic polymer binder.PBXs are used in a variety of conventional engineering and aerospace applications.Understanding and modeling the mechanical response and damage behavior of PBX are critical to developing an accurate predictive capability to address potential survivability and safety issues.First of all,the dynamic mechanical properties of PBX have been investigated by using the split Hopkinson bar technique.Based on the split Hopkinson bar technique,the thickness of the specimen and the shape of the incident wave were designed to ensure the rationality of the experimental results.Passively confined dynamic impact experiments on PBX specimens were performed by employing aluminum jackets with split Hopkinson pressure bar.The axial and radial stress history curves were measured in the test,and the characterizations of the behavior of PBX under dynamic multi-axial loads are studied.Secondly,a constitutive relation was developed for modeling the dynamic mechanical response of PBX by using the Boltzmann superposition principle with a Prony series representation.To accomplish this aim,PBX was assayed by the relaxation tests at different temperatures,in order to apply the time-temperature superposition principle(TTSP)and raise the master curves based on WLF equation.Detailed finite element simulation were carried out to evaluate the measure accurately of the device to the material mechanical behavior.The correctness of the constitutive relation was verified by comparison the finite element simulations with the experiments.Good agreements are obtained.Besides,the basis for this work was Mori and Tanaka's effective medium theory.The micromechanical inclusion method was developed to study the viscoelastic problem of PBX.The master relaxation modulus curves of polymer binder were obtained by the time-temperature superposition principle(TTSP).The relaxation constitutive relations of particulate reinforced composites were investigated by Laplace transformation and the corresponding principle.The theoretical prediction coincides with experimental results.The uniaxial and multiaxial impact tests of PBX samples were conducted to generate various damage by using a light gas gun,then examining damage and fracture of the high binder content PBX under both uniaxial and multiaxial loading.The experimental setup under multiaxial loading conditions was deliberately designed to recycle specimens more easily without a second the damaged samples.The damage modes and the corresponding failure mechanisms of the PBX specimens under different loading conditions were analyzedFinally,a constitutive model with damage has been developed for PBX.The classic theory of crack instability and growth assumes that cracks grow at high speed when the applied stress exceeds a critical level causing cracks to become unstable using.The generalized Maxwell model and micro cracks model were coupled by using strain rate superposition principle.Based on the constitutive model with damage for simulating the dynamic mechanical behavior of PBX,the damage behavior of PBX under dynamic deformation was predicted.Experimental results show that the established constitutive model can accurately characterize the impact damage response of PBX.This article provided the basis and technical guidance for the dynamic mechanical propreties of PBX and impact damage research,and also a tool for the design of energetic composites and the results can be used to establish macromesoscopic model that can be used to assess the performance of energetic composites.