Metal/polymer reactive materials have been studied and applied in a wide range of ways in recent years. This type of material is insensitive under normal conditions but reacts violently and releases a large amount of chemical energy under high-speed impact or high strain rate loading conditions. Compared with conventional explosives, it has better mechanical properties, and its unit mass energy is several times that of TNT. In this paper, PTFE/Al/CuO reactive materials are the main research objects, and we assess the impact energy release abilities of this type of reactive material through experimental research. To this end, eight sets of material formulations are designed, and the effects of particle size, the ratio of PTFE/Al and Al/CuO materials, and sintering on the energy release ability of the reactive materials are investigated. All experiments are carried out based on a self-designed new energy release testing device. The experimental device can measure the pressure time history curve generated by the reactive materials, and the rationality of the pressure time history curve can also be verified by the displacement time curve of the piston. The results show that with an increase in the Al/CuO thermite content, the energy release rate of the reactive material clearly increases, which is attributed to the reaction threshold of Al/CuO being low and because the heat generated can promote the reaction of PTFE/Al. The energy release rate of the nano-scale reactive materials is higher than that of the micron-scale reactive materials because the reduction in particle size results in a larger specific surface area. Thus, the energy required for ignition is lower. The energy release rate of sintered reactive materials is higher than that of unsintered reactive materials, which can be explained by the interfacial area between Al particles and PTFE particles in sintered reactive materials being larger, which makes the reaction more sufficient. The self-designed energy release testing device for the reactive materials and the conclusions obtained in this paper have clear significance for guiding engineering applications.
The shaped charge tandem warhead is an effective weapon against the ERA (explosive reactive armor). Whether the pre-warhead can reliably initiate the ERA directly determines the entire performance of the tandem warhead. The existing shaped charge pre-warhead mostly adopts a metal shaped jet, which effectively initiates the ERA, but interferes the main shaped jet. This article, on the other hand, explores the possibility of producing a pre-warhead using a low-density material as the liner. The nonlinear dynamic analysis software Autodyn-2D is used to simulate and compare three kinds of low-density shaped jets, including floatglass, Lucite, and Plexiglas, to the copper shaped jet in the effectiveness of impacting ERA. Based on the integrative criteria (including u-d initiation criterion, explosive reactive degree, explosive pressure, and particle velocity of the panels), it can be determined whether the low-density shaped jet can reliably initiate the sandwich charge. The results show that the three kinds of low-density shaped jets can not only initiate the reaction armor, but are also superior to the existing copper shaped jet in ductility, jet tip velocity, jet tip diameter, and the mass; namely, it is feasible to use the low-density material shaped jet to destroy the ERA.
Metal/fluoropolymer materials are typical reactive materials. Polytetrafluoroethylene (PTFE)/Al/CuO reactive materials were studied in this research. Scanning electron microscopy (SEM), quasi-static compression, the Split Hopkinson pressure bar test, and the drop hammer test were used to study the mechanical properties and induced reaction characteristics of the reactive materials with different Al/CuO thermite contents and different particle sizes. SEM images of the samples demonstrate that the reactive materials were mixed evenly. The compression test results show that, if the particle size of PTFE was too small, the strength of reactive materials after sintering was reduced. After sintering, with the increase in the content of Al/CuO thermite, the strength of the micro-sized PTFE/Al/CuO firstly increased and then decreased. The Johnson-Cook constitutive model can be used to characterize the reactive materials, and the parameters of the Johnson-Cook constitutive model of No. 3 reactive materials (PTFE/Al:Al/CuO = 3:1) were obtained. The reliability of the parameters was verified by numerical simulation. Drop hammer tests show that the addition of Al/CuO aluminothermic materials or the use of nano-sized PTFE/Al reactive materials can significantly improve the sensitivity of the material. The research in this paper can provide a reference for the preparation, transportation, storage, and application of reactive materials.found that adding a high-strength metal material, such as W, with a similar particle size to the PTFE/Al reactive material, can effectively increase the strength of the reactive materials. Cai et al. [12] used a drop hammer to find that the W particle-PTFE interface separation provided initiation and propagation of cracks. In general, the addition of W can increase the strength of the reactive material but reduce the energy density. Thus, people considered adding materials that can release energy, such as Ni. After adding Ni to PTFE/Al, Wu et al. [16] found that Ni makes the reactive material brittle, but it can increase the strain-hardening modulus and compressive strength of the material, while the heat released by the material also increased. However, the energy density of PTFE/Al reactive material is very high, and the energy of PTFE/Al reactive material cannot be significantly increased by adding Ni. If the energy release efficiency of the PTFE reactive materials can be effectively improved, it will be beneficial for their application. PTFE filler metal is a very common type of engineering material. The C-F bonds in PTFE are usually stable and do not react with metals. Under high-temperature conditions, PTFE rapidly decomposes into small-molecule fluorides and undergoes a rapid exothermic reaction with active metals [18]. Experiments by Ames [19] showed that, when the PTFE/Al reactive material impacts the target at a velocity of 1.2 km/s, the energy release efficiency still does not exceed 20%. Therefore, one of the biggest problems with PTFE/Al reactive materials is that the energy release ...
Currently, PTFE/Al is widely used in the reactive fragmentation warhead. However, for the same explosive yield, the reactive fragments usually have a smaller damage-radius than the inert fragments because PTFE/Al has a poor penetration ability and needs an impact-speed up to 1000 m/s to stimulate its chemical reaction. To enhance the damage power of reactive fragments, six kinds of reactive materials (PTFE/Al, PTFE/B, PTFE/Si, PTFE/Al/B, PTFE/Al/Si, and PTFE/Al/CuO) based on PTFE were designed and studied. Through the drop weight system and the self-designed energy release test device, qualitative and quantitative analysis of the energy release ability of six kinds of reactive materials were carried out. The qualitative analysis results indicate that the reactions of PTFE/B and PTFE/Si are weak under the impact of drop hammer with only a very weak fire light produced, while the reactions of PTFE/Al, PTFE/Al/B, PTFE/Al/Si, and PTFE/Al/CuO are relatively intense, and the reaction of PTFE/Al/Si is the most intense. Through the self-designed energy release test device, the energy release ability of the reactive material was quantitatively compared and analyzed. The results show that the energy release ability of the four formulations were as follows: PTFE/Al/Si > PTFE/Al/CuO > PTFE/Al/B > PTFE/Al. Therefore, it can be concluded that the PTFE/Al/Si formulation is a new reactive material with strong energy release ability, which can be a new choice for reactive fragment.
In order to more realistically reflect the penetrating and crushing process of a PELE (Penetration with Enhanced Lateral Efficiency) projectile, the stochastic failure algorithm and crack-softening algorithm were added to the corresponding material in this paper. According to the theoretical analysis of the two algorithms, the material failure parameters (stochastic constant γ, fracture energy Gf, and tensile strength σT) were determined. Then, four sets of simulation conditions ((a) no crack softening, (b) no stochastic failure, (c) no crack softening and no stochastic failure, and (d) crack softening and stochastic failure) were designed to qualitatively describe the influences of the failure algorithms, which were simulated by the finite element analysis software AUTODYN. The qualitative comparison results indicate that the simulation results after adding the two algorithms were closer to the actual situation. Finally, ten groups of simulation conditions were designed to quantitatively analyze the coincidence degree between the simulation results and the experimental results by means of two parameters: the residual velocity of the projectile and the maximum radial velocity of fragments. The results show that the simulation results coincide well with the experimental results and the errors were small. Therefore, the ideas proposed in this paper are scientific, and the conclusions obtained can provide guidance for engineering research.
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