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The time-sequenced damage behavior of the reactive projectile impacting double-layer plates is discussed. The analytical model considering the combined effect of kinetic and chemical energy is developed to reveal the damage mechanism. The influences of impact velocity and reactive projectile chemical characteristics on the damage effect are decoupled analyzed based on this model. These analyses indicate that the high energy releasing efficiency and fast reaction propagation velocity of the reactive projectile are conducive to enhancing the damage effect. The experiments with various reactive projectiles impact velocity increasing from 702 to 1385 m/s were conducted to verify this model. The experimental results presented that, the damage hole radius of the rear-plate increases with the increase of impact velocity. At the impact velocity of 1350 m/s, the radius of damage hole formed by PTFE/Al/Bi2O3, PTFE/Al/MoO3, PTFE/Al/Fe2O3 projectile on the rear-plate become smaller in sequence. These results are consistent with the analytical model prediction, demonstrating that this model can predict the damage effect quantitatively. This work is of constructive significance to the application of reactive projectiles.

HNS-IV (Hexanitrostilbene-IV) is the main charge of the exploding foil initiators (EFI), and the microstructure of the HNS will directly affect its density, flowability, sensitivity, and stability. HNS microspheres were prepared using droplet microfluidics, and the particle size, morphology, specific surface area, thermal performance, and ignition threshold of the HNS microspheres were characterized and tested. The results shown that the prepared HNS microspheres have high sphericity, with an average particle size of 20.52 μm (coefficient of variation less than 0.2), and a specific surface area of 21.62 m2/g (6.87 m2/g higher than the raw material). Without changing the crystal structure and thermal stability of HNS-IV, this method significantly enhances the sensitivity of HNS-IV to short pulses and reduces the ignition threshold of the slapper detonator to below 1000 V. This will contribute to the miniaturization and low cost of EFI.

The equation of state (EOS) for energetic structural materials (ESMs) has been drawn a great attention due to the absent comprehensive understanding on the effect of the shock-induced chemical reaction. In this paper, the shock compression behavior of Ni/Al ESM is investigated by developing the EOS, which mainly considers the effects of the chemical reaction and the reaction products. The chemical reaction is based on the Avram-Erofeev kinetic law and the Arrhenius equation. The study concerns the shock pressure, the relative volume, the temperature, and the chemical reaction during the shock compression. The effects of the initial porosities, the stoichiometric ratios and inert additives were mainly discussed. The results showed that high porosity would induce high temperature rise. Different stoichiometric ratios would produce different temperature rise. When the stoichiometric ratio Ni: Al ​= ​1:1, the temperature rise is highest. In addition, the inert additive material would obviously reduce the temperature rise. Finally, the developed model improved the temperature calculation, compared with the existing model.

The dynamic formation, shock-induced inhomogeneous temperature rise and corresponding chemical reaction behaviors of PTFE/Al reactive liner shaped charge jet (RLSCJ) are investigated by the combination of mesoscale simulation, reaction kinetics and chemical energy release test. A two-dimensional granular model is developed with the randomly normal distribution of aluminum particle sizes and the particle delivery program. Then, the granular model is employed to study the shock-induced thermal behavior during the formation and extension processes of RLSCJ, as well as the temperature history curves of aluminum particles. The simulation results visualize the motion and temperature responses of the RLSCJ at the grain level, and further indicate that the aluminum particles are more likely to gather in the last two-thirds of the jet along its axis. Further analysis shows that the shock, collision, friction and deformation behaviors are all responsible for the steep temperature rise of the reactive jet. In addition, a shock-induced chemical reaction extent model of RLSCJ is built based on the combination of the Arrhenius model and the Avrami-Erofeev kinetic model, by which the chemical reaction growth behavior during the formation and extension stages is described quantitatively. The model indicates the reaction extent highly corresponds to the aluminum particle temperature history at the formation and extension stages. At last, a manometry chamber and the corresponding energy release model are used together to study the macroscopic chemical energy release characteristics of RLSCJ, by which the reaction extent model is verified.

The damage effects of fluid-filled submunition payload impacted by the kinetic kill vehicle (KKV) are investigated by simulations and ground-based experiments. Numerical simulations showed that the damage level and number of submunitions were significantly influenced by the diameter of the KKV compared with its length. Based on that, a high velocity penetrator formed by shaped charge explosion was used to simulate the direct hit experiment of a KKV impacting submunition payload. Experimental results demonstrated that the damage modes of submunitions mainly included the slight damage, perforation and total smash, showing a good agreement with the simulations. To understand the multiple damage modes of submunitions, the damage behavior of the submunitions in direct hit process were analyzed based on the AUTODYN-3D code. Numerical results presented that increased KKV diameter can increase the crater diameter and expand the damage volume, which will achieve a higher direct hit lethality. Further analysis indicated that there were other mechanical behaviors can enhance the damage to submunitions not lying in the KKV flight path, such as secondary debris kill, neighboring submunitions collision with each other, and high-speed fluid injection effect.

In this paper, the reaction characteristic and its application in shaped charge warhead of a novel reactive material, which introduced copper (Cu) and plumbum (Pb) into traditional polytetrafluoroethylene/aluminum (PTFE/Al), are studied. The thermal analysis and chemical reaction behavior of the PTFE/Al/Cu/Pb mixture are investigated by Differential Scanning Calorimetry (DSC),Thermo-gravimetry (TG), and X-ray Diffraction (XRD) techniques. Then, the shaped charge liners with PTFE/Al/Cu/Pb reactive materials are fabricated, and the X-ray experiments show that they could form reactive jets with excellent performance under the detonation effects of the shaped charge. Based on that, the penetration experiments of shaped charge with PTFE/Al/Cu/Pb reactive liner against steel plates are carried out, and the results demonstrate that the PTFE/Al/Cu/Pb reactive jets could produce a deeper penetration depth compared to the traditional PTFE/Al reactive jets. Meanwhile, the PTFE/Al/Cu/Pb reactive jets also show significant inner-blast effects, leading to dramatically cracking or fragmentation behavior of the penetrated steel plates. This new PTFE/Al/Cu/Pb reactive liner shaped charge presents enhanced penetration behavior for steel targets that incorporates the penetration capability of a high-density and ductility jet, and the chemical energy release of PTFE-matrix reactive materials.

Penetration and internal blast behavior of reactive liner enhanced shaped charge against concrete space were investigated through experiments and simulations. The volume of the enclosed concrete space is about 15 m3. The reactive liner enhanced shaped charge utilizes reactive copper double-layered liner, which is composed of an inner copper liner and an outer reactive liner, while the reactive material liner is fabricated by PTFE/Al (Polytetrafluoroethylene/Aluminum) powders through cold-pressing and sintering. Static explosion experiments show that, compared with the shaped charge which utilizes copper liner, the penetration cavity diameter and spalling area of concrete by the novel shaped charge were enlarged to 2 times and 4 times, respectively. Meanwhile, the following reactive material had blast effect and produced significant overpressure inside the concrete closed space. Theoretical analysis indicates concrete strength and detonation pressure of reactive material both affect the penetration cavity diameter. To the blast behavior of reactive material inside the concrete space, developing TNT equivalence model and simulated on AUTODYN-3D for analysis. Simulation results reproduced propagation process of the shock wave in concrete space, and revealed multi-peaks phenomenon of overpressure-time curves. Furthermore, the empirical relationship between the peak overpressure and relative distance for the shock wave of reactive material was proposed.

Ballistic impact and sealed chamber tests were performed on the steel-encased reactive material projectile (SERMP) to understand its behind-plate overpressure effect when impacting the thin aluminum plates. The reactive material encased with a 1.5 mm thick 30CrMnSiNi2A steel shell was launched onto the initially sealed test chamber with a 3 mm thick 2024-T3 thin aluminum cover plate. Moreover, the overpressure signals in the test chamber were recorded by pressure sensors. The experimental results indicate an unusual behind-plate overpressure effect: as the density of the projectile increases from 6.43 g/cm3 to 7.58 g/cm3 by increasing the content of tungsten powder, although its total chemical energy decreases, it produces a higher behind-target overpressure at a lower impact velocity. A theoretical model is proposed to predict the reaction length of reactive material inside the projectile based on one-dimensional shock wave theory to understand this unexpected result. In addition, the deviation between the actual energy release and the theoretical calculation results, also the variation of overpressure rise time are analyzed and discussed. As the analyses show, when the SERMP successfully penetrates the cover plate, an increasing density of the reactive material inside the projectile always means that the delaying rarefaction wave effect, an increase of its internal pressure and strain rate levels. These factors lead to the increase of the overpressure limit velocity and reaction extent of the reactive material, while the overpressure rise time decreases.

Enhanced damage to the full-filled fuel tank, impacted by the cold pressed and sintered PTFE/Al/W reactive material projectile (RMP) with a density of 7.8 g/cm3, is investigated experimentally and theoretically. The fuel tank is a rectangular structure, welded by six pieces of 2024 aluminum plate with a thickness of 6 mm, and filled with RP-3 aviation kerosene. Experimental results show that the kerosene is ignited by the RMP impact at a velocity above 1062 m/s, and a novel interior ignition phenomenon which is closely related to the rupture effect of the fuel tank is observed. However, the traditional steel projectile with the same mass and dimension requires a velocity up to 1649 m/s to ignite the kerosene. Based on the experimental results, the radial pressure field is considered to be the main reason for the shear failure of weld. For mechanism considerations, the chemical energy released by the RMP enhances the hydrodynamic ram (HRAM) effect and provides additional ignition sources inside the fuel tank, thereby enhancing both rupture and ignition effects. Moreover, to further understand the enhanced ignition effect of RMP, the reactive debris temperature inside the kerosene is analyzed theoretically. The initiated reactive debris with high temperature provides effective interior ignition sources to ignite the kerosene, resulting in the enhanced ignition of the kerosene.

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multi-spaced plates. The reactive jet produces mechanical perforations on the spaced plates by its kinetic energy (KE), and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration reaction. In the present study, the chain damage behavior is initially demonstrated by experiments. The reactive liners, composed of 26 wt%Al and 74 wt% PTFE, are fabricated through a pressing and sintering process. Three reactive liner thicknesses of 0.08 CD, 0.10 CD and 0.12 CD (charge diameter) are chosen to carry out the chain damage experiments. The results show a chain rupturing phenomenon caused by reactive jet. The constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position, which consequently determines the number of ruptured plates behind the armor. Then, the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates, based on the mechanism of behind armor debris (BAD). The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism, the behind armor blast (BAB), has acted on the ruptured plates. Finally, a theoretical model is used to consider the BAB-induced enhancement, and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations, the mass of reactive materials, and the thickness of plates.

Force chains based mesoscale simulation is conducted to investigate the response behavior of aluminum-polytetrafluoroethylene (Al-PTFE) granular composites under a low-velocity impact. A two-dimensional model followed the randomly normal distribution of real Al particles size is developed. The dynamic compressive process of Al-PTFE composites with varied Al mass fraction is simulated and validated against the experiments. The results indicate that, force chains behavior governed by the number and the size of agglomerated Al particles, significantly affects the impact response of the material. The failure mode of the material evolves from shear failure of matrix to debonding failure of particles with increasing density. A high crack area of the material is critical mechanism to arouse the initiation reaction. The damage maintained by force chains during large plastic strain builds up more local stresses concentration to enhance a possible reaction performance. In addition, simulation is performed with identical mass fraction but various Al size distribution to explore the effects of size centralization and dispersion on the mechanical properties of materials. It is found that smaller sized Al particle of composites are more preferred than its bulky material in ultimate strength. Increasing dispersed degree is facilitated to create stable force chains in samples with comparable particle number. The simulation studies provide further insights into the plastic deformation, failure mechanism, and possible energy release capacity for Al-PTFE composites, which is helpful for further design and application of reactive materials.

The formation and separation behaviors of tandem EFPs are studied by the combination of experiments and simulations. The results show that different formation and separation processes can be obtained by adjusting the double-layer liners, and simulations agree with experiments well. Then, the interaction process between the two liners is discussed in details, and the formation and separation mechanism are revealed. It can be found that there are four phases in the formation and separation processes, including impact phase, propulsion phase, slide phase and free flight phase. During the impact phase, the velocities of two liners rise in turns with kinetic energy exchange. In the propulsion phase, the axial impact becomes insignificant, but the radial interaction between two liners influences the appearance of tandem EFPs. Meanwhile, it should be mentioned that the inner surface of foregoing EFP remains to be in contact with the outer surface of following EFP in the propulsion phase, and the following one would continue to push the foregoing one for about 10μ to 20 μs, causing the velocities of following and foregoing EFPs gradually decreasing and increasing respectively. In the slide phase, an obvious relative movement occurs between the two EFPs, and there would be barely kinetic energy exchange. Then, the two EFPs separate gradually and get into the phase of free flight. Generally, if the outer and inner liners have the same thickness, the outer copper-inner copper liners form two long EFPs, the outer copper-inner steel liners become a foregoing short steel EFP and a following long copper EFP, and the outer steel-inner copper liners produce a foregoing long copper EFP and a following conical steel EFP. In addition, thickness match also has an important impact on formation appearance and separation process for both outer copper-inner copper liners and outer steel-inner copper liners. With the thickness ratio of outer liner to inner liner decreasing, the length and length-diameter ratio of both foregoing and following EFPs increase gradually.

In this research, the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated. Six particularly selected sintering temperatures, three different cooling modes (annealing cooling, normalizing cooling and rapid cooling), three different initial cooling temperatures, as well as six different final cooling temperatures were designed to compare the effects of sintering temperature, cooling rate, initial cooling temperature and final cooling temperature on the properties of reactive materials. Geometry distortion was quantitatively analyzed by a statistic on the dimensional changes of the specimens and microscopic morphology. A mechanical response properties transition from brittle to ductile was found and analyzed. By combining the thermodynamic properties of PTFE and unsteady heat conduction theory, mechanisms of cooling induced morphology change, temperature induced distortion and strength decrease were obtained. The results showed that the cooling rate has the most significant effect on the morphology transformation, while initial cooling temperature has more significant effect on the dimensional distortion than final cooling temperature. As to the mechanical properties transition from brittle to plastic, a more prominent effect of initial cooling temperature than cooling rate and final temperature was revealed.

Impact experiments of large-caliber PELE with various inner-outer diameter ratio perforating RHA plate at low velocity were performed. Experimental results showed the size of perforated holes on plate, average diameter of damage area on witness plate, and number of behind-armor fragments will increase as d/D increasing from 0.72 to 0.84. Expansion and fragmentation of large-caliber PELE in this condition were also numerically studied with ANSYS Autodyn. Then, an analytical model accounting for an additional radial shock wave was presented to predict radial expansion velocity and fragmentation of jacket, as well as an empirical approach to estimate diameter of damage area. Calculation results by these approaches were in good agreement with experiments and numerical simulations. Further discussion revealed that Shock/rarefaction wave interactions behavior varying with inner-outer diameter ratio is an important mechanism resulting in different lateral effect by PELE projectiles with various configurations. Keywords: PELE, Enhanced lateral effect, Penetration mechanics, Behind-armor fragments

Reactive material projectiles can be an extremely efficient lethality enhancement technology that incorporates the defeat mechanisms of chemical energy and kinetic energy. This paper presents such a research on the enhanced ignition behavior of reactive material projectiles impacting a fuel-filled tank. Firstly, the ignition process description of the fuel-filled tank impacted by inert metal and reactive material projectiles is presented. Secondly, ballistic impact experiments are performed to investigate the ignition effects of the fuel-filled tank impacted by reactive material versus tungsten alloy projectiles with mass matched. The fuel tank used for the experiments is a cylindrical steel casing structure filled with aviation kerosene and sealed with aluminum cover plates on both ends using screw bolts. The experimental results indicate that, compared with impacts from tungsten alloy projectiles, there is dramatically enhanced structural damage to the fuel-filled tank and an enhanced ignition effect caused by reactive material projectile impacts. Finally, an analytical model is developed, by which the effects of the aluminum cover plate thickness on critical structural failure energy of the fuel-filled tank and the total energy of the reactive material projectile deposited into the fuel-filled tank are discussed. The analysis shows a good agreement with the experiments. Keywords: Reactive materials, Fuel-filled tank, Chemical energy release, Ignition mechanism

Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge (RLSC) are investigated by experiments and simulations. The reactive materials liner with a density of 2.3 g/cm3 is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380 °C. Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of 0.5, 1.0, and 1.5 CD (charge diameter), respectively. The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff, while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff. To understand the unusual experimental results, numerical simulations based on AUTODYN-2D code are conducted to discuss the wave shaper effect, including the propagation behavior of detonation wave, the velocity and temperature distribution of reactive jet, and penetration depth of reactive jet. The simulations indicate that, compared with RLSC without wave shaper, there is a higher temperature produced inside reactive jet with wave shaper. This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline, which results in significantly decreasing its penetration performance. Keywords: Shaped charge, Reactive materials liner, Wave shaper, Reactive jet, Penetration performance

In this paper, the ballistic impact experiments, including impact test chamber and impact double-spaced plates, were conducted to study the reaction behaviors of a novel functionally graded reactive material (FGRM), which was composed of polytetrafluoroethylene/aluminum (PTFE/Al) and PTFE/Al/bismuth trioxide (Bi2O3). The experiments showed that the impact direction of the FGRM had a significant effect on the reaction. With the same impact velocity, when the first impact material was PTFE/Al/Bi2O3, compared with first impact material PTFE/Al, the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates. The theoretical model, which considered the shock wave generation and propagation, the effect of the shock wave on reaction efficiency, and penetration behaviors, was developed to analyze the reaction behaviors of the FGRM. The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials. The conclusion of this study provides significant information about the design and application of reactive materials. [ABSTRACT FROM AUTHOR]