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In order to study the morphology characteristics of the PTFE/Al reactive shaped charge jet and the chemical reaction during the jet formation, PTFE/Al reactive liners with aluminum particle sizes of 5 μm and 100 μm were prepared. The parameters of the Johnson–Cook constitutive model of PTFE/Al reactive materials (RMs) were obtained through quasi-static compression experiments and SHPB (Split Hopkinson Pressure Bar) experiments. X-ray imaging technology was used to photograph the shape of reactive shaped charges jet at two different time points. The AUTODYN secondary development technology was used to simulate the jet formation, and the simulation results are compared with the experimental results. The results show that the simulation results are close to the experimental results, and the error is in the range of 4–8%. Through analysis, it is observed that the RMs reacted during the PTFE/Al reactive shaped charge jet formation, and due to the convergence of the inner layer of the liner during the jet formation, the chemical reaction of the jet is from inside to outside. Secondly, the particle size of aluminum powder has an influence on the chemical reaction and morphology of the jet. During the jet formation, there were fewer RMs reacted when the PTFE/Al reactive liners were prepared with 100 μm aluminum powder. Compared with 5 μm aluminum powder, when the aluminum powder is 100 μm, the morphology of the jet is more condensed, which is conducive to generating greater penetration depth.

Formation behaviors of rod-like reactive shaped charge penetrator (RRSCP) and their effects on damage capability are investigated by experiments and numerical simulations. The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used. Three types of spherical-segment aluminum-polytetrafluoroethylene-copper (Al-PTFE-Cu) reactive liners with Cu contents of 0%, 46.6%, and 66% are fabricated and tested. The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect, but the tail skirts disappear over time. Moreover, rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact. From simulation analysis, the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning, forming a leading reactive penetrator and a following chemical energy cluster. The unique formation structure determines the damage modes of the aluminum plate and the steel plate. Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content. With increasing Cu content, the velocity, activation extent, and reaction extent of Al-PTFE-Cu RRSCP decrease, which contribute to elongation and alleviate the negative effects of chemical reactions on elongation, significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration. However, the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

The penetration-deflagration coupling damage performance of rod-like reactive shaped charge penetrator (RRSCP) impacting thick steel plates is investigated by theoretical analysis and experiments. A penetration-deflagration coupling damage model is developed to predict the penetration depth and cratering diameter. Four type of aluminum-polytetrafluoroethylene-copper (Al-PTFE-Cu) reactive liners with densities of 2.3, 2.7, 3.5, and 4.5 g·cm−3 are selected to conduct the penetration experiments. The comparison results show that model predictions are in good agreement with the experimental data. By comparing the penetration depth and cratering diameter in the inert penetration mode and the penetration-deflagration coupling mode, the influence mechanism that the penetration-induced chemical response is unfavorable to penetration but has an enhanced cratering effect is revealed. From the formation characteristics, penetration effect and penetration-induced chemical reaction behaviors, the influence of reactive liner density on the penetration-deflagration performance is further analyzed. The results show that increasing the density of reactive liner significantly increases both the kinetic energy and length of the reactive penetrator, meanwhile effectively reduces the weakened effect of penetration-induced chemical response, resulting in an enhanced penetration capability. However, due to the decreased diameter and potential energy content of reactive penetrator, the cratering capability is weakened significantly. •A theoretical model for the penetration-deflagration coupling damage performance of RRSCP is developed.•The influence mechanism of penetration-induced chemical response on penetration and cratering capabilities is revealed.•The influences of reactive liner density on the penetration-deflagration performance of RRSCP are discussed.

The formation process of reactive materials shaped charge is investigated by X-ray photographs and numerical simulation. In order to study the formation process, a trans-scale discretization method is proposed. A two-dimensional finite element model of shaped charge and reactive material liner is established and the jet formation process, granule size difference induced particle dispersion and granule distribution induced jet particle distribution are analyzed based on Autodyn-2D platform and Euler solver. The result shows that, under shock loading of shaped charge, the Al particle content decreases from the end to the tip of the jet, and increases as the particle size decreases. Besides, the quantity of Al particles at the bottom part of the liner has more prominent influence on the jet head density than that in the other parts, and the Al particle content in the high-speed section of jet shows inversely proportional relationship to the ratio of the particle quantity in the top area to that in the bottom area of liner.

Ni/Al energetic structural materials have attracted much attention due to their high energy release, but understanding their thermal reaction behavior and mechanism in order to guide their practical application is still a challenge. We reported a novel understanding of the thermal reaction behavior and mechanism of Ni/Al energetic structural materials in the inert atmosphere. The reaction kinetic model of Ni/Al energetic structural materials with Ni:Al molar ratios was obtained. The effect of the Ni:Al molar ratios on their thermal reactions was discussed based on the products of a Ni/Al thermal reaction. Moreover, depending on the melting point of Al, the thermal reaction stages were divided into two stages: the hard contact stage and soft contact stage. The liquid Al was adsorbed on the surface of Ni with high contact areas, leading in an aggravated thermal reaction of Ni/Al.

A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles (RMPs) impacting liquid-filled tanks, and the corresponding hydrodynamic ram (HRAM) was studied in detail. PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process. The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s. The corresponding cavity evolution characteristics and HRAM pressure were recorded by high-speed camera and pressure acquisition system, and further compared to those of steel and aluminum projectiles. Significantly different from the conical cavity formed by the inert metal projectile, the cavity formed by the RMP appeared as an ellipsoid with a conical front. The RMPs were demonstrated to enhance the radial growth velocity of cavity, the global HRAM pressure amplitude and the front panel damage, indicating the enhanced HRAM and structural damage behavior. Furthermore, combining the impact-induced fragmentation and deflagration characteristics, the cavity evolution of RMPs under the combined effect of kinetic energy impact and chemical energy release was analyzed. The mechanism of enhanced HRAM pressure induced by the RMPs was further revealed based on the theoretical model of the initial impact wave and the impulse analysis. Finally, the linear correlation between the deformation-thickness ratio and the non-dimensional impulse for the front panel was obtained and analyzed. It was determined that the enhanced near-field impulse induced by the RMPs was the dominant reason for the enhanced structural damage behavior. •Enhanced structural damage behavior of RMPs impacting liquid-filled tanks was verified.•Impact-induced fragmentation/deflagration led to an ellipsoidal cavity with a conical front.•Damage effect strongly depends on the initial kinetic energy and the initiation ratio.•The enhanced front panel damage is closely related to the enhanced near-field impulse.•Combined effect of kinetic energy and chemical energy is the determinant mechanism.

Composite concrete structures, commonly found in urban infrastructures, such as highways and runways, are pivotal research object in the protection field. To study the dynamic response of composite concrete structures subjected to reactive jet penetration coupled with an explosive effect, a full-scale damage experiment of composite structures under the action of 150 mm caliber shaped charges was performed, to derive the dynamic damage modes of different concrete thicknesses under the combined kinetic and chemical energy damage effects. The results indicated that under aluminum jet penetration, concrete layers exhibited minor funnel craters and penetration holes. However, concrete layers displayed a variety of damage modes, including central penetration holes, funnel craters, bulges, and radial/circumferential cracks when subjected to the PTFE/Al jet. The area of the funnel crater expanded as the thickness of the concrete increased, while the height of the bulge and the number of radial cracks decreased. The diameter of penetration holes increased by 76.9% and the area of funnel crater increased by 578% in comparison to Al jet penetration damage. A modified-RHT concrete model that reflected concrete tensile failure was established, utilizing AUTODYN. Segmented numerical simulations of damage behavior were performed using the FEM-SPH algorithm and a restart approach combined with reactive jet characteristics. The spatial distribution characteristic of the reactive jet and the relationship between kinetic penetration and explosion-enhanced damage were obtained by the simulation, which showed good concordance with the experimental results. This study provides important reference data and a theoretical basis for the design of composite concrete structures to resist penetration and explosion.

Many scholars have used experimental research methods to conduct extensive research on the impact energy release behavior of Polytetrafluoroethylene(PTFE)/Al reactive materials. However, in numerical simulation, PTFE/Al still lacks the calculation parameters of impact energy release behavior. In order to obtain the simulation parameters of PTFE/Al impact ignition, the Hill mixture law was used to calculate the material parameters of PTFE/Al (mass ratio 73.5/26.5), and according to the Hugoniot curve of PTFE/Al and the γ state equation, the JWL equation of state of a PTFE/Al unreacted substance and reaction product was fitted with a genetic algorithm. According to the PTFE/Al impact energy release experiment, the parameters of the PTFE/Al chemical kinetic equation were determined, and the parameters of the trinomial reaction rate equation were fitted. The obtained parameters were used in the simulation calculation in LS-dyna to predict the damage of the aluminum target plate under the impact of the PTFE/Al reactive fragments.

Fractal theory is introduced in fracture surface research of alkali-slag concrete (ASC) under freeze-thaw cycles; crack distribution of ASC fracture surface and freeze-thaw damage zone were calculated. Through fractal analysis of ASC sample fracture surfaces, relevance between section fractal dimension and fracture toughness and relationship between material composition and section fractal dimension are clarified. Results show that the specimen’s cracks before freeze-thaw extend along force direction gently, and there are more twists and turns after freezing and thawing; the fractal dimension D also grows from 1.10 to 1.33. SEM internal microcracks’ D of ASC internal microstructure after freezing and thawing is 1.37; 0 to 300 times ASC fractal dimension under freezing and thawing is between 2.10 and 2.23; with freeze-thaw times increasing, ASC fracture toughness decreases and fractal dimension increases, the fractal dimension and fracture toughness have a good linear relationship, and the fractal dimension can reflect the toughening effect of ASC. It is very feasible to evaluate ASC fracture behaviour under freezing and thawing with the fractal theory. Fractal dimension generally increases with activator solution-slag (A/S for short) or slag content. The greater the amount of A/S or slag content, the lower the dimension.