Abstract:Aluminized explosives have been widely applied due to their high energy density and pressure output. To further enhance the secondary combustion reaction and pressure output of aluminized explosives， graded structure is designed inspired by the microstructure of bamboo. In this work， the radially-graded structured HMX/Al （RGS-HMX/Al） cylinders with three layers containing different sizes and content of Al were prepared through 3D direct writing technology. The effects of Al distribution on combustion and pressure output properties of graded HMX/Al were fully studied. For the RGS-HMX/Al cylinder with Al content of 10%， 20%， and 30% distributed from inner to outer layer， the combustion reaction and flame propagation of inner layer were faster than that of outer layer. And the pressure （2337.61 kPa） was higher than that of RGS-HMX/Al cylinder with Al content in the reverse distribution. For the RGS-HMX/Al cylinder containing Al of 10 μm， 5 μm， and 160 nm distributed from inner to outer layer， a slow combustion process with sparse bright Al droplets was observed. Moreover， the highest peak pressure （1512.65 kPa） was obtained for the RGS-HMX/Al cylinders with nAl in the middle layer， which exhibited much higher pressure output than that homogeneous HMX/Al cylinder. More importantly， bimodal pressure was observed for the RGS-HMX/Al cylinders with Al of 10 μm in the middle layer.

Abstract:In order to explore the effects of structure on combustion performance of aluminum/polytetrafluoroethylene （Al/PTFE）-based reactive materials and improve combustion performance of fluorine-based thermite， additive manufacturing technology （3D printing） was utilized to prepare Al/PTFE-based reactive materials with solid， hollow， core-shell， and confined hollow structures， as well as Al/CuO-based and Al/Fe₂O₃-based reactive materials with confined hollow structures. The microstructure， thermal performance， combustion rate， and gas production performance were assessed by scanning electron microscope （SEM）， differential scanning calorimetry （DSC）， high speed camera， and constant volume combustion chamber. The results show that each sample exhibits intact structure and uniform components. Under the circumstance of same mass， the samples with core-shell and confined hollow structures display lower heat release than that of samples with solid and hollow structures. The burning rate of samples with hollow， core-shell， and confined hollow structures is 1.44， 1.32， and 2.62 times higher than that of samples with solid structure， respectively. Obvious improvement in gas production performance and pressurization rate appears for samples with hollow and confined hollow structures， especially for samples with confined hollow structure. The burning rate of Al/PTFE， Al/CuO， and Al/Fe₂O₃ materials with confined hollow structure is significantly higher than that of corresponding samples with solid structure， particularly for Al/Fe₂O₃ materials. The approach to regulate combustion performance of lines by preparing materials with hollow structure is expected to provide a novel idea for designing new high-performance weapons.

Abstract:In order to increase the energy of the secondary reaction of composite explosives， the novel composite oxidant ammonium perchlorate （AP）-lithium perchlorate （LiP） was prepared by solvent evaporation method. Scanning electron microscope （SEM） and X-ray diffractometer （XRD） were used to test and characterize the morphology， and crystal structure of the sample. The thermal decomposition properties of the samples were analyzed by differential scanning calorimetry （DSC）. The underwater explosion power parameters of three polymer bonded explosives （PBXs） containing composite AP-LiP， mechanical mixture AP-LiP and AP were evaluated by electrometric method. The results show that， for composite AP-LiP， the crystal morphology is fairly regular， the crystal surface is smooth， the particle size distribution is fairly uniform， and no agglomeration is observed. Composite AP-LiP has a high degree of crystallization and a fairly complete crystal structure. The thermal decomposition performance of composite AP-LiP is better than that of mechanical mixture AP-LiP. The underwater explosion results show that， compared with the AP-containing PBX， the shock wave energy， bubble energy， and total energy of underwater explosion of PBX containing composite AP-LiP increase by 0.098-0.154， 0.254 MJ·kg^-1 and 0.352-0.408 MJ·kg^-1 respectively， and the energy decays slower as the distance increases.

Abstract:In order to study the aluminum-water reaction characteristics of PVA-nAl/HTPB， the PVA-nAl/HTPB composites were prepared by dispersing nAl/HTPB in the polyvinyl alcohol （PVA）， which was obtained by physical cross-linking method. In order to explore the aluminum-water reaction mechanism， the aluminum-water reaction characteristics of the polyvinyl alcohol-nAl/HTPB with 0.1 mol·L^-1 NaOH solution at different temperatures （25， 40， 55， 70， 85 ℃ and 100 ℃））were investigated and the residue after the aluminum-water reaction were characterized. The results show that the maximum hydrogen production and rate of PVA-nAl/HTPB is 76 mL·g^-1 and 80 mL·g^-1·min^-1， respectively， which is higher than that of PVA-nAl. The product of the aluminum-water reaction is aluminium oxyhydroxide （AlO（OH））.

Abstract:In order to obtain the damage characteristics of polytetrafluoroethylene/aluminum （PTFE/Al）， five PTFE/Al reactive liners with different Al particle sizes， by mold pressing and sintering， were prepared acting on double spacered plates . The results show that with the increase of Al particle size from 10 μm to 200 μm， the broken hole area， equivalent broken hole diameter ，broken hole uplift height and the volume of damaged area of steel and aluminum targets both decrease. When Al particle size is 10 μm， the damaged parameters of steel target are S_steel=0.4 CD （charge diameter）， h_steel=0.48 CD， V_steel=420 cm³， and the damaged parameters of aluminum target are S_aluminum=3.82 CD， h_aluminum=1.72 CD， V_aluminum=2280 cm³. PTFE/Al reactive jet with Al particle size 50 nm/70 μm can significantly improve the perforation effect of steel target， and d_steel=0.59 CD. Based on the experimental data， the analysis model of rupturing damage effect of reactive jet on behind-tagert is obtained by fitting.

Abstract:The tandem warhead with high-speed kinetic fragment and coated reactive material has both high-speed penetration and chemical energy damage effect. This paper is aimed to research its tandem damage effect on shielded charges. The impact dynamics model of impacting on shielded charges by the high-speed kinetic fragment and coated reactive material was established. By combining the excitation theory of reactive materials with the initiation criterion of shielded charges， the impact damage to the shielded charges by the high-speed kinetic fragment and coated reactive material was calculated and analyzed. Based on the 2D-Autodyn platform， the initiation process of shielded charges impacted by the high-speed kinetic fragment and coated reactive material was simulated. The comparison verifies the consistency between theoretical calculation and numerical simulation. By Combining theoretical analysis and numerical simulation results， the main influencing factors of the damage to shielded charges， the probable damage modes and the transition conditions between each damage mode were discussed. The results show that there are five damage modes for the shielded charges impacted by the high-speed kinetic fragment and coated reactive material ， including the forepart penetration initiation mode （Ⅰ）， the main part penetration initiation mode （Ⅱ）， the no reactive material reaction and no penetration initiation mode （III）， the reactive material reaction enhanced initiation mode （Ⅳ） and the reactive material reaction and no initiation mode （Ⅴ）. When the structure and material properties are determined， the main influencing factors of damage modes are the impact speed and shielding thickness. The theoretical model established in this paper can predict the above damage modes well.

Abstract:The dynamic energy release characteristics of the PTFE-based energetic liner are related to the damage effect of the jet to the target. In this paper， the dynamic overpressure of energetic and aluminum jets in a quasi-closed chamber was measured by static explosion test. The jet energy release and energy release efficiency were obtained by theoretical calculation. The results showed that the energetic liner underwent a deflagration reaction during the forming process， and the overpressure peak of the energetic jet can be increased by 3 times to 4 times compared with that of aluminum jet. For PTFE/Ti energetic liner， in the content range of 0% to 70%， as the tungsten content increased， the jet energy release decreased. But the energy release efficiency was improved due to the increased explosive driving load and the intensified friction between tungsten particles and active metals. For PTFE/Ti energetic liner， in the mass range of 13-30 g， as the mass of the liner increased， the jet energy release was improved. But the energy release efficiency dropped due to the decreased forming pressure of the penetrator.

Abstract:The oxidation reaction of micro and nano aluminum powder is an important way of energy release and aging inactivation. Molecular dynamics and reaction kinetics provide necessary means for elucidating the microscopic mechanism of oxidation reaction of aluminum powder and quantitatively describing the oxidation process. According to the type of reaction system， the oxidation of aluminum powder can be divided into aluminum-oxygen （Al-O₂）， aluminum-water （Al-H₂O） and aluminum-other oxides （Al-other oxides） reaction systems. The recent progress of molecular dynamics and reaction kinetics in the above reaction systems is reviewed. The mechanism of oxidation kinetics of aluminum powder and its key influencing factors， including the oxide layer， particle size， atomic diffusion rate， temperature and oxygen concentration， were discussed， which proved the flexibility and effectiveness of molecular dynamics and reaction kinetics. On this basis， the important problems in different oxidation reaction systems were analyzed and prospected. It is pointed out that the oxidation kinetics of aluminum powder under multiple factors， the kinetics of Al-water vapor reaction， and the intrinsic mechanism of Al-other oxides reaction are the key problems to be solved in the future.

Abstract:As the arch structure is one of the common structural forms of underground engineering， the majority of current research focuses on the numerical simulation. The numerical results of structural damage characteristics and response lack corresponding experimental verification， which cannot sufficiently guide the blast resistance design of underground engineering. In order to study the failure mode and blasting resistant performance of underground arch structures with reinforced concrete under explosive load， 5 independent experiments under top explosion had been carried out with different blasting distances and charges. Results show that the damage degree of the arch structure gradually increases with the increase of charge under the same blasting distance. The characteristics of failure mode developed from the concrete cracks at the back surface of blast to the concrete spalling and deformation of steel bars. At last， the concrete collapsed significantly at the center of the vault and the steel bars were severely bent and deformed. The damage of the arch structure under top explosion is not only related to the scaled distance， but also affected by the blasting distance. Under the same scaled distance，the damage degree of arch structure increases significantly with the increase of blasting distance. By analyzing the relationships between the displacement response and the charge mass， the displacement response and the blasting distance， a method is initially proposed for dividing the damage grade based on the deflection-span ratio， which provides experimental support for the structural failure evaluation and analysis in the future.

Abstract:To improve the penetration depth in the target subjected to the jet of reactive materials liner， a shaped charge with Al/Ni-Cu double-layered reactive liners based on the K-charge structure was proposed. The outer and inner liner of the double-layered reactive liner are made of oxygen-free copper and Al/lNi reactive material， respectively. Experimetal study of jet formation， static armor-piercing into steel ingots and the penetration power to typical concrete targets were carried out seperately by using X-ray cinematography. Results show that the double-layered reactive liners with K-charge can form a continuous jet after detonation with obvious pit areas in steel and concrete targets. However， the jet has no obvious reaming effect on penetrating the target. A combined damage effect of kinetic energy and chemical reaction can be achieved by the Al/Ni-Cu double-layered reactive liners. Compared with the Cu-Cu double-layered， less jet accumulated in the target penetrated by the new double-layered reactive linears. Meanwhile， the penetration depth and volume of the steel targets were increased by 20.1% and 23.0%， respectively， while the penetration depth and volume of the concrete targets were increased by 17.2% and 45.6%， respectively.

Abstract:To achieve an effective evaluation of the damage power of all-energetic penetration warhead， a test system for damage power assessment was established based on the 125mm artillery， accompany by a description in multiple physical fields from various aspects such as penetration， reaming， high temperature， high pressure， and arson ignition by arson. Results show that a 16 kg warhead can penetrate a 5-layered steel target at a speed of 952 m·s^-1 to form strong fire which lasts for about 120 ms， with a maximum diffusion range of over 6 m×10 m and a maximum temperature of about 2100 ℃. Compared with the inert warhead， the gains of temperature and overpressure at 1.2 m are about 1270 ℃ and 0.16-0.5MPa， respectively， and the cumulative gain of the broken hole area of 5-layered steel target reaches beyond 300%. Moreover， the warhead has a good arson ignition effect on the fuel tank.

Abstract:Six preparation methods of physical mixing， ball milling， vapor deposition， electrostatic spray/spinning， solvent/non-solvent and 3D printing for aluminum-fluoro reactive materials are summarized. Recent research progress of Al-fluoropolymer reactive materials are reviewed from the aspect of product performance and method advantages and disadvantages. The reaction process of aluminum-fluoropolymer reactive materials at slow heating rate and fast heating rate are introduced. The promising research directions in the future are pointed out， including design a new method that combines the advantages of various preparation methods and more attention should be paid to strengthen the research on the reaction mechanism of aluminum-fluoropolymer reactive materials when heated.