Search

3-nitro-1,2,4-tri-azol-5-one (NTO) is a high energy insensitive explosive. To study the shock initiation process of NTO-based polymer bonded explosive JEOL-1 (32%octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 32% NTO, 28% Al and 8% binder system), the cylinder test, the gap experiments and numerical simulation were carried out. Firstly, we got the detonation velocity (7746 m/s) and the parameters of Jones-Wilkins-Lee (JWL) equation of state (EOS) for detonation product by cylinder test and numerical simulation. Secondly, the Hugoniot curve of unreacted explosive for JEOL-1 was obtained calculating the data of pressure and time at different Lagrangian positions. Then the JWL EOS of unreacted explosive was obtained by utilizing the Hugoniot curve as the reference curve. Finally, we got the pressure growth history of JEOL-1 under shock wave stimulation and the parameters of the ignition and growth reaction rate equation were obtained by the pressure-time curves measured by the shock-initiation gap experiment and numerical simulation. The determined trinomial ignition and growth model (IG model) parameters can be applied to subsequently simulation analysis and design of insensitive ammunition with NTO-based polymer bonded explosive.

Cadmium sulfide nanorods with a length of 69 nm have been prepared by using Cd(OAc)2.2H2O and S8 at 125 °C in the presence of triethylenetetramine as the template agent and coordination agent and characterized by using X-ray diffraction, transmission electron microscopy, FTIR, photoluminescence, and UV–vis absorption spectroscopic techniques. Photocopolymerization of glycidyl methacrylate (GMA) and sodium acrylate (SA) was carried out using CdS nanorods as a photocatalyst under UV light exposure at 400 nm in the presence of β-cyclodextrin (β-CD). To optimization of the effective parameters on the synthesis of copolymer nanocomposite, the amounts of initiator, monomers, and β-CD, duration of pre-deoxygenation, and light wavelength were evaluated. Ring opening of poly(GMA-co-SA)/CdS nanocomposite with NaN3 afforded poly(HAzPMA-co-SA)/CdS nanocomposite and subsequent mixing with RDX in DMF led to the formation of poly(HAzPMA-co-SA)/RDX/CdS nanocomposite as a polymer bonded explosive. All of the copolymer nanocomposites were characterized using various tools of instrumental analysis.

This work investigates kinetics and thermal decomposition behaviors of pentaerythritol tetranitrate (PETN) and two polymer-bonded explosive (PBX) samples created from PETN (named as PBX-PN-85 and PBX-PP-85) using the vacuum stability test (VST) and thermogravimetry (TG/DTG) techniques. Both model-free (isoconversional) and model-fitting methods were applied to determine the kinetic parameters of the thermal decomposition. It was found that kinetic parameters obtained by the modified Kissinger–Akahira–Sunose method (using non-isothermal TG/DTG data) were close to those obtained by the isoconversional and model-fitting methods that use isothermal VST data. The activation energy values of thermal decomposition reactions were 125.6–137.1, 137.3–144.9, and 143.9–152.4 kJ·mol−1 for PBX-PN-85, PETN, and PBX-PP-85, respectively. The results demonstrate the negative effect of the nitrocellulose-based binder in reducing the thermal stability of single PETN, while the polystyrene-based binder seemingly shows no adverse influence on the thermal decomposition of PETN in our presented PBX compositions.

Thermal stimuli is one of the major external stiumuli resulting from an overheated explosion of a munition. In order to evaluate the influence of external thermal stiumuli on the thermal hazards of JEOL-1 (32 wt% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 32 wt% 3-nitro-1,2,4-triazole-5-one (NTO), 28 wt% Al and 8 wt% binder system) explosive, accelerating rate calorimeter (ARC) is used to study the adiabatic thermal decomposition properties of JEOL-1 molding powders, and the slow cook-off properties of JEOL-1 are studied by experimental test and numerical simulation. The activation energy Ea, pre-exponential factor A, mechanism function f(α) and self-accelerating decomposition temperature (SADT) of adiabatic thermal decomposition of JEOL-1 molding powders are obtained according to ARC results. The response level of JEOL-1 polymer bonded explosive (PBX) columns exposed to an engulfing liquid pool fire is examined by the slow cook-off test. The ignition location, ignition temperature, ignition time and the transient temperature distributions of JEOL-1 PBX columns during the slow cook-off are obtained by numerical simulation. It can be concluded from this study that JEOL-1 is a low vulnerable explosive with high thermal safety.

To satisfy the energy and security requirements of the explosives, it is necessary to develop high-energetic low vulnerable explosive. As the representatives of high-energetic explosives and low vulnerable explosives, hexanitrohexaazaisowurtzitane (HNIW) and 3-nitro-1,2,4-triazole-5-one (NTO) are used to research high-energetic low vulnerable polymer-bonded explosive (PBX) in this study. Based on the formulation of PAX-11 (94 mass% HNIW, 2.4 mass% CAB, 3.6 mass% BDNPA/F), some HNIW is replaced by NTO to reduce the vulnerability of the PBX during this work. Solution−water suspension method was used to prepare a series PBXs with different formulations. The explosion probability method, differential scanning calorimeter and accelerating rate calorimeter are used to evaluate the hazards of different PBX molding powders. And the thermal vulnerabilities, mechanical properties and energy levels of PBX columns are assessed by slow cook-off tests, tensile strengthes and detonation velocities, respectively. Moreover, finite element numerical simulations are adopted to study the transient temperature distributions, ignition time and ignition locations of the PBX columns during slow cook-off. The investigated results show that when the mass fraction of HNIW and NTO is 50% and 44%, respectively, the PBX passes the slow cook-off test and the detonation velocity reaches 8685 m s−1. To balance the energy and vulnerability of the PBXs, we obtain a high-energetic low vulnerable PBX formulation (50 mass% HNIW, 44 mass% NTO, 2.4 mass% CAB, 3.6 mass% BDNPA/F, 0.5 mass% additional graphite) which can be used in the warhead of the high-explosive anti-tank cartridge.

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.

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is one of the most widely used explosives. Problems about phase state and unrecoverable damage are significant in the application of HMX and HMX-based polymer-bonded explosive (PBX). Recently, the acceleration of δ- to β-HMX retransformation in humid atmosphere was reported. However, the function of water was not well understood. In this paper, we studied the mixed phase during δ- to β-HMX-d8 retransformation with neutron diffraction. Evidence of γ-HMX-d8 is specially focused to estimate whether the hydrated phase is part of the δ- to β- phase retransformation. Besides, in situ high-pressure neutron diffraction of HMX-based PBX was performed to study the evolution of intergranular strains in special structures such as twin plane, cleavage planes, and slip systems. We observed an abnormal release of strain on certain planes under applied pressure which had not been reported. This abnormal phenomenon was considered to explain the formation of microcrack...

Mesoscale simulation using the material point method (MPM) was conducted to study the pressure&ndash, volume (PV) variations of Octahydro-1,3,5,7-Tetranitro-1,2,3,5-Tetrazocine (HMX)/Estane polymer-bonded explosive (PBX) under impact loading. The PV isotherms and Hugoniot data were calculated for the different porosities and binder volume fractions. The PV isotherms were used to determine the parameters for the Birch&ndash, Murnaghan equation of state (EOS) for the PBX. From the EOS, the isothermal bulk modulus (K0) and its pressure derivative () were calculated. Additionally, the pseudo particle velocity and pseudo shock velocity variations were used to obtain the bulk wave speed c and dimensionless coefficient s for the Mie&ndash, Gr&uuml, neisen EOS. The simulations provide an alternative approach for determining an EOS that is consistent with experimental observations.

Complexities of heating mechanisms make it difficult to investigate the safety of a polymer bonded explosive (PBX) charge of earth-penetrating-weapons (EPWs) during penetration. In this paper, the dynamic damage and non-shock initiation of PBX1314 (60 wt % hexahydro-1, 3, 5-trinitro-1, 3, 5-s-triazine (RDX), 16 wt % aluminum, 24 wt % hydroxy-terminated polybutadiene (HTPB)) during penetration is investigated through experiments and simulations. In the experiments, steel projectiles filled with PBX1314 are launched to penetrate concrete targets. In the results, non-shock initiations occur on the tail surface of PBX1314 along with mechanical damage of the tail and middle part of PBX1314. A dynamic damage and initiation model is proposed to characterize the effects of microcracks on the mechanical and thermal responses of PBX1314. Investigation based on the model suggests that microcrack interfacial friction plays significant roles in damage, heat generation and localization in PBX1314. A non-shock initiation criterion is developed based on macroscale variables in PBX1314. Numerical simulations of the penetration experiments are performed by using the proposed model and criterion. The mechanical damage and non-shock initiation of PBX1314 in the experiments are successfully predicted. The simulation results indicate that the tail of PBX1314 impacts the projectile repeatedly during penetration. Finally, the initiation criterion is satisfied because of frictional heat localization near microcrack surfaces and initiation is activated in the tail of PBX1314.

Synergetic deformation behavior between crystal particles and polymeric binders dominates the machinability of energetic materials. In the present work, we elucidate cutting mechanisms of HMX-based polymer bonded explosive (PBX) in orthogonal cutting by numerical simulations based on a cohesive finite element framework. The polygonal HMX crystals with a particle volume fraction of 90% are modeled by a linear elasticity model, while the HTPB binders are described by a rate-independent hyperelastic model coupled with a rate-dependent plasticity model. Furthermore, cohesive elements are implemented in both crystal particles and binders to describe thermal-mechanical coupling-induced material failure behavior in the cutting process of PBX. Simulation results reveal different deformation modes of PBX, as well as their correlations with machining results. Furthermore, it is found that depth of cut has a strong impact on the cutting processes of PBX, in terms of material failure mode, subsurface damage and energy dissipation. These findings provide important guidelines for the design and synthesis of energetic materials with high machinability. Keywords: Energetic material, Synergetic deformation, Orthogonal cutting, Finite element simulation, Cohesive zone model

Surface engineering has been widely implemented in materials science for multipurpose functionalization. However, the rational design of surface structure with both adhesiveness and toughness remains a huge challenge. Herein, a facile and general strategy has been demonstrated for coating of energetic crystal 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) via in situ copolymerization of catechol and amino functionalized monomers. The design principle is on the basis of bioinspired supramolecular chemistry, providing the synergistic effect of covalent and noncovalent interactions. Compared with the pristine HMX crystal, the coated HMX crystals exhibited significantly improved phase-transition stability and reduction of impact/friction sensitivity owing to the reinforced interfacial strength and coating roughness. Moreover, thanks to incorporation of the catechol–containing synthetic polymer (CSP) interlayer, the interfacial interaction between HMX crystal and fluoropolymer binder was noticeably enhanced, leading to markedly improved mechanical strength (both tensile and compression strength were improved by over 40%), as well as creep resistance (the creep strain was decreased by over 55%) for the resulted polymer bonded explosive (PBX) composite. Therefore, the present work provides an effective and universal method for the construction of environmental adaptive energetic materials on account of their reduced sensitivity, enhanced mechanical strength and thermal stability, which were favorable for their practical applications.

Polymer bonded explosive (PBX) is a particle-matix composite consisting of explosive particles, polymer matrix/binder, and the interface between the particles and the binder, and the particle volume fraction (PVF) in the PBX is extremely high. To simulate the meso-scale deformation and damage behaviors of PBX with the numerical manifold method (NMM), a bilinear cohesive contact relationship (BCCR) model with three parameters is incorporated in the NMM to describe the particle-binder interface, a visco-elastic constitutive model of prony series with 22 parameters is incorporated in the NMM to describe the polymer binder, and a fracturing algorithm based on the maximum tensile stress criterion and the Mohr–Coulomb criterion is employed to describe the fracturing failures of the particles as well as the binder. The PBX meso-scale deformation and damage process of microcrack initiation, crack propagation and formation of crack bands under tensile or compressive conditions are studied through NMM simulations, and the influenes of the PVF and the explosive particle geometrical distribution (PGD) on PBX mechanical performaces are specially investigated. This work enables and proves the NMM to be an promissing roubust numerical tool for further simulation studies of the meso-scale mechanical performances of PBX, as well as other particle-fillled polymer composites.

A micromechanical model for the thermoelasticity of polymer-bonded composites is presented. The model is particularly aimed at describing materials where the polymeric binder phase undergoes non-negligible thermal expansion affecting the overall thermoelastic response. Constitutive choices for modeling a mixed binder-void interphase layer are proposed, and an associated decomposition of total eigenstrains into classical, elastic imperfection (damage), and binder thermal expansivity parts is examined within the context of imperfect inter-particle interfaces. A novel temperature dependent modified Eshelby tensor is identified, making possible the development of a temperature dependent modified self-consistent homogenization scheme—what we call the M $\theta$ -SCH model. A method for distinguishing between dispersed and isolated parts of the binder and void phases in the model is also provided, along with a description of particle coating (or interphase) thickness derived from particle morphology and mesoscale effective properties. Although the theory is general, its development is motivated by the need to model anisotropic and highly nonlinear observed thermal expansion behavior of the polymer bonded explosive PBX 9502, for which model simulations are performed and compared with existing measurements.

The application of in situ structural health monitoring in polymer bonded explosive materials through the introduction of carbon nanotubes into the binder phase is investigated through piezoresisti...

Nano-fillers have attracted a large amount of attention in enhancing the mechanical properties of polymer bonded explosive (PBX), due to the strong interfacial interactions. However, the addition of inert components reduces the energy output and makes the processing, recycling and re-utilization of energetic composites quite unfavorable. To improve the mechanical properties while maintaining detonation performance, a novel self-reinforced PBX was constructed with very low content of nano-1,3,5-triamino-2,4,6-trinitrobenzene (TATB) served as modifiers. The incorporation of nano-TATB particles into PBX evidently increased the storage modulus, strength, and toughness. The enhanced mechanism could be ascribed to the nano effect of nanoparticles and “interlocking block” formed on the rough surface of nano-TATB, which provided stronger interfacial interaction. This work demonstrates the successful application of nano-energetic crystals to self-reinforce PBXs, thereby opening up new perspectives in structure design and modification of mechanical properties for energetic composites without changing the intrinsic components of energetic composites.

Polymer bonded explosives (PBX) are kind of particulate-reinforced composite materials in which interface interaction is of great significance to its structural and mechanical features. In this work, effect of temperature and strain rate on the microstructure, mechanical properties and fracture damage mechanism of TATB-F2314 are studied using molecular dynamics simulations. The TATB layers at the TATB-F2314 interface are deformed, leading to a rough and undulate surface that facilitates the formation hydrogen bonds between TATB and F2314. Intermixing phase is characterized for the first time at the TATB-F2314 interface. The interfacial structures and mechanical properties of TATB-F2314 depend strongly on temperature and strain rate. F2314 experiences a ductile-to-brittle transition at its glass transition temperature, which exerts great influence on the structural evolution and failure mechanism of TATB-F2314. The fracture mainly appears on F2314 under a quasi-static or low strain rate tension but transfers to TATB layers near to the interfacial intermixing phase at a high strain rate. Our simulations reveal the effect of temperature and strain rate on the microstructure, mechanical behavior and fracture damage mechanism of TATB-F2314 interface, which is useful for the design, preparation and safe use of PBX.

Material characterization at high strain rates under simultaneous compression and shear loading has been a challenge due to the differing normal and shear wave speeds. An experimental technique utilizing the compression Kolsky bar apparatus was developed to apply dynamic compression and shear loading on a specimen nearly simultaneously. Synchronization between the compression and shear loading was realized by generating the torsion wave near the specimen which minimizes the time difference between the arrival of the compression and torsion waves. This modified Kolsky bar makes it possible to characterize the dynamic response of a material to combined compression and shear impact loading. This method can also be applied to study dynamic friction behavior across an interface under controlled loading conditions. The feasibility of this method is demonstrated in the dynamic characterization of a simulant polymer bonded explosive material.

The thermal decomposition kinetics of the interesting polycyclic nitramine cis-1,3,4,6- tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) and its polymer bonded explosive (PBX) based on polyurethane matrix, have been investigated using different thermal analysis techniques and methods. The used polyurethane matrix is based on hydroxyl-terminated polybutadiene (HTPB) cured by hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used nonisothermally, whereas the vacuum stability test (VST) was used isothermally. Kinetic parameters were determined by using isoconversional (model-free) methods. Furthermore, the Advanced Kinetics and Technology Solution (AKTS) software was used to determine the kinetic parameters of the studied samples in order to provide a comparison. It was found that the decomposition temperature of BCHMX/HTPB is lower than that of pure BCHMX. All the applied techniques as well as computational results showed that BCHMX/HTPB has a lower activation energy than pure BCHMX. The different methods used, Kissinger, Ozawa, Flynn, and Wall (OFW) and Kissinger-Akahira-Sunose (KAS) methods presented activation energies in the same range of the AKTS software results. Also the results proved that VST technique could be a useful tool to present results suitable for calculation of the kinetic parameters of explosives.

In this work, inspired by the strong chemical adhesion of mussels, a facile and noncovalent in situ polymerization of dopamine approach has been employed to coat 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystals. The resultant polydopamine (PDA) coated TATB (pTATB) core–shell particles are subjected to in-depth characterizations. It has been demonstrated that a dense graphite-like structure PDA is uniformly coated on the surfaces of TATB crystals. By optimization of the reaction time, pH value and temperature, the morphology and thickness of the PDA layer on TATB crystals were finely controlled on a nanometer scale. Then, the pTATB was further used as the solid filler of a typical polymer bonded explosive (PBX). It has been shown that the PBX containing pTATB exhibited significantly improved tensile and compression strength or strain, and creep resistance, due to the strong interfacial interactions at the PDA interlayer. Moreover, the mechanical properties could be further improved by using more PDA content. This work demonstrates an effective and fundamental surface modification method to enhance the interfacial interaction between crystalline particles and binders, resulting in improved mechanical properties.

Material Point Method (MPM) mesoscale simulation was used to study the constitutive relation of a polymer bonded explosive (PBX) consisting of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and a fluorine polymer binder F2314. The stress-strain variations of the PBX were calculated for different temperatures and different porosities, and the results were found to be consistent with experimental observations. The stress-strain relations at different temperatures were used to develop the constitutive equation of the PBX by using numerical data fitting. Stress-strain data for different porosities were used to establish the constitutive equation by fitting the simulation data to an improved Hashion-Shtrikman model. The equation can be used to predict the shear modulus and bulk modulus of the PBX at different densities of the sample. The constitutive equations developed for TATB/F2314 PBX by MPM mesoscale simulation are important equations for the numerical simulations of the PBX at macroscale. The method presented in this study provides an alternative approach for studying the constitutive relations of PBX.

The ultrasonic attenuation coefficient is sensitive to the internal constituent components of the material, and the effective entry of ultrasonic waves into the material is of great significance for the development of non-destructive testing. In this paper, based on DIGIMAT/FE, a mesoscopic model of materials is built, covering two phases of explosive particles and binder, using ABAQUS/EXPLICT to load ultrasonic loading of materials, extracting internal unit stress-time curves and stress wave propagation clouds, and establishing the relationship between the ultrasonic attenuation coefficient of the bonded explosive and the different mass ratio of the explosive particles. Taking the RDX/Estane composite adhesive as an example, the volume fraction of explosive particles RDX and the influence of ultrasonic frequency on the sound attenuation coefficient were studied. The numerical simulation results of the model were compared with the real experimental data to verify the validity of the model. This numerical model method can effectively guide the acoustic experimental process of the material and provide a theoretical basis for the non-destructive testing of materials.

Using Digimat-FE, a representative volume element (RVE) model was constructed that reflects the true mesostructure of PBX explosives. The model consists of three phases of explosive particles, binder and pores. Through Digimat-MF, various factors affecting the effective elastic modulus of PBX explosives were investigated, including the elastic modulus, volume fraction, morphology, gradation, porosity and pore diameter of the explosive particles. The calculation results show that the higher the volume fraction of explosive particles, the larger the effective elastic modulus of PBX, and the increase of the effective elastic modulus of PBX is obviously increased when the volume fraction exceeds 60%. The morphology of the explosive particles has little effect on the effective elastic modulus of the PBX explosive, while the grading of the explosive particles has a great influence. The existence of pores makes the effective elastic modulus of PBX explosives significantly reduced, and the increase of porosity makes the effective elastic modulus decrease exponentially; the increase of pore diameter makes the effective elastic modulus of PBX explosives decrease.

Polymer-bonded explosives are solid high-explosive particles that exhibit brittle behavior in uniaxial tension, quasi-brittle in uniaxial compression, and ductile when subjected to high confining pressure. Tension cracking is the primary failure mode of polymer-bonded explosives quasi-brittle solid, which will lead to overall failure of structural integrity. One characteristic of brittle or quasi-brittle solids, such as polymer-bonded explosives, is that when subjected to overall compressive loading, the tensile cracks will initiate inside the material due to existence of imperfection within the materials. In this study, extended finite element method is applied to analyze the cracking failure mechanism in the PBX 9502 plate-like specimen with cavity subjected to overall compression. The nonlinear constitutive behaviors and failure of polymer-bonded explosives under complex stress states were described by means of stress state–dependent strength surface, non-associated flow rule, and cohesive failure model. Analysis indicates that the tensile stress around the cavity arises in the specimen under overall compression, and this local tensile stress will lead to cracking initiation. The comparison between simulation results and the experimental data reported by Liu and Thompson shows that they are in agreement with each other on some aspects of crack behaviors, including overall development of crack history and inflection, crack initiation moment, and crack initial speed.

We investigate the effects of porosity and chemical reactivity on the shock initiation of an HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)-based polymer bonded explosive due to thin flyer impact using two-dimensional mesoscale simulations. Microstructural samples are computationally generated, and the calculated shock response is compared to experiments. The sample dimensions are 0.1 × 1.05 mm2, and each sample accounts for grain scale heterogeneities, including randomized grain morphology and pore spacing. Simulations are performed using the Lawrence Livermore National Laboratory (LLNL) arbitrary Lagrangian–Eulerian multi-physics code ALE3D. Chemistry and equation of states are handled with LLNL's thermochemical code Cheetah. We employ a modified Arrhenius-based chemical kinetics model that scales the temperature exponent fitting parameter with flyer shock conditions. This new model is calibrated to the mean response of experimental shock initiation thresholds for three separate Kapton flyer thicknesses. A simplified shock initiation criterion is proposed, which classifies the macroscale initiation response based on cross-sectional temperature profiles of the shocked sample. This criterion is used to further investigate the probabilistic response of the sample to variations in the mean porosity and chemical kinetics rate, and we find an inverse correlation between the shock pressure and the confidence interval of the experimental threshold velocity. The methodology presented in this work for quantifying the probabilistic nature of shock initiation is material agnostic. These mesoscale studies may be used to inform continuum scale models and expedite the development of future, tailored energetic formulations.

To improve thermal stability and security of energetic materials, the core–shell structured FOX-7 (1,1-diamino-2,2-dinitroethylene)/F2602 (fluoroelastomer) PBX (polymer bonded explosive) was prepared from recrystallized FOX-7 by a spray drying strategy. The morphology and crystal form of the recrystallized FOX-7 were retained, and the mean particle size of the FOX-7/F2602 PBX was apparently reduced from 39.72 µm of raw FOX-7 to 1.50 µm. SEM, TEM, and XPS analysis showed that F2602 was deposited on the surface of FOX-7 to form a core–shell structured composite. The formation mechanism of the core–shell composite was proposed. Compared with the recrystallized FOX-7 grains, the prepared FOX-7/F2602 PBX had higher apparent Ea and Tb, which signifies improved thermal stability and thermal safety. The impact sensitivity test showed that the critical height value (H50) of the FOX-7/F2602 composite had remarkable enhancement, indicating better mechanical security. This work provides a simple and effective method to prepare the core–shell structured energetic composite with enhanced safety performance.

In order to study the crack formation mechanism of an aluminized polymer-bonded explosive (PBX) under tensile stress, a Brazilian test was carried out on the aluminized PBX grains with different densities. In addition, the microscopic morphologies of the samples after the Brazilian test were characterized. The experimental results show that the process of crack formation includes initiation, propagation, and final formation; the cracks are generated by the accumulation of microscopic defects and they expand gradually from the interior to the end surface of grains. With increasing grain density, as well as the curing process, the critical stress values could be significantly improved during the formation of cracks. The formation mechanism of the cracks is not transcrystalline fracture but interfacial debonding, which was observed using scanning electron microscopy.

The influence of an explosion-driven deformation on the defect structure in RDX crystals embedded in a polymer-bonded explosive was investigated by means of confocal scanning laser microscopy. The images were compared to the defect structure in the as-received RDX grades, embedded