The Ubiquitiformal Characterization of the Mesostructures of Polymer-Bonded Explosives.

A nesting ubiquitiform (NU) approach was developed to characterize the mesostructural features of polymer-bonded explosives (PBXs), and then used to predicate some equivalent physical properties of PBXs, which can also be expected to be extended to other composites with complicated internal mesostructures. To verify the availability, two NU models for two kinds of PBX with different compositions are presented, which are PBX 9501 and LX-17, based on which, the equivalent thermal conductivities were calculated. Particularly, it is so encouraging that an analytical expression of the equivalent thermal conductivity was obtained only under a simply assumption of homogeneity. Moreover, it was found that the numerical results calculated by both the recursive algorithm and the analytical expression were in good agreement with the experimental data. In addition, it is also shown that such a physical property as the equivalent thermal conductivity is indeed independent of the meso-configuration of the location distribution of the explosive particles and the voids inside the PBX, which seems consistent with the common expectations and lays the foundations for the application of ubiquitiform to investigating some equivalent properties of composites.

Shock initiation of multi-component insensitive PBX explosives: Experiments and MC-DZK mesoscopic reaction rate model.

To facilitate the pre-estimation and optimization of the prescription design of a multi-component polymer bonded explosive (PBX), a multicomponent mesoscopic reaction rate model (MC-DZK model) is developed to predicate preferably the influence of both the explosive components and the particle size of on the shock initiation. All the parameters in the model are determined directly by the parameters in the DZK model for each explosive component. Furthermore, for the multicomponent insensitive explosive PBXC10 (70% TATB, 25% HMX, and 5% Kel-F800 by weight) with different explosive particle sizes, both shock initiation experiments and corresponding numerical simulations are performed, and there is satisfactory agreement between the numerical results and the available experimental data. It is found that the pressure histories present as a shape of step increase during the whole shock initiation process, which is resulted mainly from the rapid chemical reaction rate just behind the precursory shock wave front. It is also found that the smaller the size of the explosive particulates, the faster the pressure grows on the precursory shock wave front, the shorter the run distance to detonation, and the higher the chemical reaction rate just behind the precursory shock wave front.

Mechanical Behavior of Liquid Nitrile Rubber-Modified Epoxy Resin under Static and Dynamic Loadings: Experimental and Constitutive Analysis.

Quasi-static and dynamic compression experiments were performed to study the influence of liquid nitrile rubber (LNBR) on the mechanical properties of epoxy resin. The quasi-static experiments were conducted by an electronic universal machine under strain rates of 0.0001/s and 0.001/s, while a Split Hopkinson Pressure Bar (SHPB) system was adopted to perform the dynamic tests for strain rates up to 5600/s. The standard Zhu-Wang-Tang (ZWT) nonlinear viscoelastic model was chosen to predict the elastic behavior of LNBR/epoxy composites under a wide range of strain rates. After some necessary derivation and data fitting, a set of model parameters for the tested materials were finally obtained. Meanwhile, the incremented form of the ZWT nonlinear viscoelastic model were deduced and implemented into the user material program of LS-DYNA. A simulation-test contrast had been performed to verify the validity and feasibility of the algorithm. The results showed that the viscoelastic behavior of epoxy resin can be effectively simulated.