JOURNAL OF ENERGETIC MATERIALS
Year:2014 | Volume:9 | Issue:2 (23)|Papers Count:8

This paper presented a method to investigate plastic deformation of FCC metals in high strain rates. Experimental set up included two stages gas gun, spherical projectile and target assembly. Target assembly included front plate, two pressure bars, specimen, three frames and rigid holder. The proposed method is based on designing and optimizing of split Hopkinson bar to evaluate stress-strain diagrams in oxygen-free high thermal conductivity copper. Modifications included sketch of experiments to achieve plane stress waves in input pressure bar. The experimental results were compared with 3D finite element simulation. Also, the effect of projectile velocity, specimen thickness, front plate thickness and distance between impacted projectile and center of front plate were investigated. It was concluded that decreasing specimen thickness and appropriate calibration of gas gun to shot projectile to the center of front plate, are appropriate ways to achieve strain rates more than 104 s-1 in the specimen.

2-Methyl aziridine is used as an intermediate in different industries and is one of the compounds that recently has attracted many attentions in order to reduce its production cost. This compound is mainly applied in the defence industries as solid fuel missiles. Among the procedures reported for its large scale production, the Wenker procedure has been used widely. However, in recent two decades, this method is replaced by dehydration of alkanol amines on the surface of catalyst supports in the gas phase, because the Wenker procedure suffers from some main drawbacks such as long processing time, costly production and production of large amounts of wastes, etc. In this study, 2-methyl aziridine was prepared from the intramolecular dehydration reaction of isopropanol amine on the surface of SiO2 nanocatalyst in the gas phase; then effects of various parameters including catalyst composition, catalyst component’s ratio, calcination temperature and different operating conditions on the activity of the catalyst were investigated. After choosing the best catalyst with high activity, XRD, TEM, SEM and BET analyses were employed to characterization and identification of the catalyst structure.. In this process, the Si1P0.06Ba0.02Cs0.06 catalyst had the best performance and gave highest yield at 400oC with 1000 hr-1 space velocity in range of 25-40 mesh of catalyst size.

Tetrazoles and their derivatives are insensitive energetic molecules that can be used in the compounding of the high energy material. Herein, two types of bishyroxyethyltetrazole compounds have been synthesized using bisnitrile and sodium azide and via consequent alkylation of the reaction product. The structure of all products have been confirmed by 1HNMR, MASS spectroscopy and elemental analysis. Also, for better interpretation of the 1HNMR spectra of bishydroxy ethyl tetrazole, the most stable conformation of 2-(5-methyl-2H-tetrazol-2-yl) ethan-1-ol (as a model molecule) have been investigated. The results of conformational analysis have indicated that the most stable conformation is gauch one. So, under basis of the 1HNMR and conformational analysis, the presence of an intramolecular hydrogen bond between -OH group and the 2-N atom of tetrazole ring in hydroxyl ethyl tetrazole compounds was confirmed.

The aim of this research is improvement of elongation at break of PBXN-109 polymer bonded explosive. Due to the great effect of isocyanate/hydroxyl ratio (r=NCO/OH) on the mechanical properties of plastic bonded explosives, the samples of PBXN-109 with different r-values of 1, 0.95, 0.85, 0.75 and 0.65 were prepared and analyzed by hardness and tensile tests. The results show that sample with r-value of 0.65 does not cure, completely. Besides, with decrement of r-value, the elongation at break of PBXN-109 increases, and tensile strength and stiffness decrease. The results of elongation at break for samples containing r-values of 1, 0.95, 0.85 and 0.75 are 8.46, 10.99, 11.64 and 26.63, respectively. According to this research, PBXN-109 with the r-value of 0.8 indicates satisfactory elongation at break and tensile strength.

In this research, stacking sequences of hybrid composites composed of aluminum plate and carbon/epoxy laminate under explosion loading have been optimized and analyzed. First, the effect of explosion wave on the stress, deflection field, and Tsai-Wu criteria has been investigated. Then, by using finite element modeling for these laminates and Response Surface Method (RSM) and Genetic Algorithm (GA), objective functions have been determined and the stacking sequences of aluminum plate and carbon/epoxy laminate were optimized. Results of this study show that change of the stacking layups can increase the resistance of FML for preventing the explosion effects as well as, providing maximum safety factor and minimum deflection.

Guanylureadinitramide is regarded as one of the most important dinitramide salts with low sensitivity and proper efficiency. Dinitramide salts such as ammoniumdinitramide and guanylureadinitramide can be used as oxidizing agents in rocket, guns and gas-producing propellant formulations. Usage of these materials with smaller particle size causes higher efficiency of the composites due to the increase of their surface area. In this study, guanylureadinitramide was obtained from potassium sulfamate salt (40% yield), and was characterized. For the preparation of the guanylureadinitramide with particles under 20 microns, the solvent/anti-solvent crystallization method was taken into account. Furthermore, influential factors on the size and shape of the particles (e.g., concentration, purity of anti-solvent, freezing and drying method) were investigated, and guanylureadinitramide crystals having particle size in the range of 20 microns to 300 nm were produced.

Concentrated suspension of binders in composite propellant causes complex phenomena so that controlling of rheology properties is difficult due to high percentage of fillers. Composite solid propellant contains paste suspension of mixtures of different components, e.g. oxidizer, fuel and binder. Increasing the percentage of solid phase without increment of viscosity is an important subject in the production of solid propellant. This problem can be solved using two different particle sizes distribution. Five samples of composite solid propellants on the basis of hydroxyl terminated polybutadiene (HTPB) with 85% of solid phase containing dual sizes of ammonium perchlorate (AP) have been prepared. These samples have different coarse/fine ratios between 80/20 to 60/40. It was found that optimum temperature for casting of propellant is greater than 40oC. The best ratio for obtaining the least viscosity is 70/30 coarse/fine ratio.