Study On Dynamic Behavior And Impact Energy Release Characteristics Of Al/PTFE Enhanced By Aluminum Honeycomb

As a metal/fluoropolymer material,Al/PTFE energetic material has the characteristics of high energy content,inert in the conventional environment,and higher strength than the traditional nitrogen-containing explosives.It can be widely used in ammunition damage,reaction protection and other fields.However,the strength of pure Al / PTFE energetic materials under dynamic loading is only tens of MPa,which seriously restricts its wide application in the context of high dynamic compressive strength requirements,and the existing reinforcement methods are at the cost of sacrificing the activity.In order to significantly improve the compressive strength of reactive materials and coordinate the contradiction between the improvement of dynamic compressive strength and the maintenance of activity,the dynamic compressive strength and activity maintenance of Al / PTFE energetic materials were achieved by filling active metal skeleton.In this paper,based on In order to significantly improve the compressive strength of reactive materials and coordinate the contradiction between the improvement of dynamic compressive strength and the maintenance of activity,the dynamic compressive strength and activity maintenance of Al / PTFE energetic materials were achieved by filling active metal skeleton.the traditional Al/PTFE energetic materials,different types of Al/PTFE energetic materials enhanced by aluminum honeycomb framework were prepared by cold pressing and sintering by adding different sizes of aluminum honeycomb framework.The dynamic mechanical behavior,strengthening mechanism and energy release characteristics of Al/PTFE energetic materials reinforced by aluminum honeycomb framework were studied by means of experiments and theoretical derivation.The results are as follows:The formulations of 20.5%Al/73.5%PTFE/6% aluminum honeycomb and24.9%Al/69.1%PTFE/6% aluminum honeycomb were determined.The wall thickness of aluminum honeycomb is 38 μm,the arm length is 1.0 mm,1.5 mm and 2.0 mm.The particle size of Al powder is 5 μm and that of PTFE is 34 μm.Based on the stress wave theory,the dynamic strength of aluminum honeycomb reinforced Al / PTFE energetic materials with different arm lengths and different aluminum content formulations was tested by a self-made split Hopkinson experimental system.The data collected by the dynamic strain gauge are processed by MATLAB software,and the experimental results describing the dynamic mechanical response of the specimen are obtained.At the same time,the high-speed image of the specimen during the loading process is analyzed,combined with the experimental results and the morphology of the specimen after loading.The results show that the arm length of aluminum honeycomb has the greatest influence on the reinforcement effect,the reinforcement effect of aluminum honeycomb framework with arm length of 1.5mm is the best,which can reach more than 100 MPa.The energy release experiments of reinforced Al/PTFE energetic materials with different aluminum honeycomb arm lengths and different aluminum content formulations under different impact velocities were carried out.Through the transient overpressure test system,the transient optical fiber pyrometer test system and the infrared thermal imager system,the overpressure change,reaction temperature change and container temperature change during the impact process of the specimen were obtained respectively.Based on the energy angle,the energy release standards of different types of specimens under different impact conditions were analyzed and calculated.The higher the specimen strength,the lower the energy release at the same impact velocity,but even so,it is higher than that of traditional Al/PTFE(26.5%/73.5%)energetic materials.On the basis of inducing the reaction,the increase of aluminum content in the specimen is helpful to improve the energy release due to the presence of oxygen in the air.The high-speed impact energy release experiment of reinforced Al / PTFE energetic material under vacuum condition was carried out.According to the single point temperature value obtained by the thermocouple,the temperature distribution of the quasi closed container body in the process of impact reaction is deduced by the heat conduction equation.Combined with the Laval nozzle effect,the pressure change in the quasi closed vessel and the reaction product temperature during impact reaction were analyzed,the threshold value of the complete reaction rate of the reinforced Al/PTFE energetic material in vacuum is 1.5km/s and the complete reaction energy release is 8.237 kJ/g.Below the threshold of the complete reaction velocity,the impact velocity of the specimen has a significant effect on the energy release results.The Johnson cook constitutive model and ZWT nonlinear thermo viscoelastic constitutive model are used to describe aluminum and polytetrafluoroethylene.Based on the superposition principle,the reinforcement effect function of aluminum honeycomb framework and the powder correction coefficient are introduced.By using the Hopkinson experimental data of two kinds of Al honeycomb reinforced Al/PTFE energetic materials(I: 20.5% Al / 73.5% PTFE / 6% aluminum honeycomb;II: 24.9%Al/69.1% PTFE/6% aluminum honeycomb),the constitutive model of the reinforced Al/PTFE energetic materials was fitted,and this model is verified through experiments.