Abstract:

Abstract:

Abstract:A high-speed camera， a high-precision pressure sensor， an R-type thermocouple and a micro-thrust test bench has been used to investigate the controllable combustion behaviors and thrust performance of the laser-controlled solid propellant （LCSP） under laser irradiation. The burning rate， ignition delay time， chamber pressure， combustion flame temperature and micro-thrust under different laser power densities were obtained. The results showed that the burning rate and chamber pressure increased linearly， while the ignition delay time decreased with increasing laser power density. Combining the thermocouple temperature curves， it was concluded that the combustion process of LCSP might be divided into five zones： pre-heating zone， condensed phase zone， triple zone， gas phase zone and flame zone. Meanwhile， the combustion flame temperature of the LCSP was 1202.3 ℃ under the laser power density of 1.343 W·mm^-2. Dependence of the combustion status on laser power density makes sense to realize the accurate adjustment of micro-thrust. In the experiment， the thrust control of LCSP is successfully realized by changing the laser power density. As the laser power density increased from 0.344 W·mm^-2 to 1.343 W·mm^-2， thrust of the LCSP increased from 1.58 mN to 2.28 mN.

Abstract:To study the biaxial compressive mechanical properties of solid propellantn， it is necessary to determine the optimal propellant specimen configuration. This configuration should be compatible with the testing machine and test fixture and meetthe requirements of biaxial deformation characteristics. Based on the finite element numerical simulation calculation， the deformation stress contour of the three-component HTPB composite solid propellant specimens with eight different configurations under biaxial compression loading were obtained. Moreover， the optimal propellant specimen configuration was verified by conducting the dynamic biaxial compressive mechanical properties test on the corresponding specimen. Results show that the stress contour of all specimens under small deformation （strain within 10%） is uniform overall. However， the requirement of the plane stress does not meet during deformation of the specimens with an aspect ratio greater than 1. Furthermore， the average value of plane stress， dispersion of plane stress， the whole stress stability factor and the stress concentration factor were selected as the optimizing objective function of the propellant specimen configuration. The contrastive analysis shows that the optimal configuration is a 25 mm cube. Finally， the validity of the above determinated optimal configuration was verified by analyzing the characteristics of stress-strain curves of the propellant specimens obtained under dynamic biaxial compressive loading condition

Abstract:In order to obtain accurate and reliable physicochemical properties of condensed phase combustion products （CCPs） of composite propellants， a method of ethylenediamine tetraacetic acid （EDTA） titration based on microwave digestion was proposed to achieve the quantitative analysis of the total components of condensed phase combustion products. Four groups of condensed phase combustion products of propellant were obtained by using self-developed condensed phase combustion products collection system. The determination accuracy of EDTA titration， inductively coupled high frequency plasma emission spectrometry （ICP）， gas volumetric method and potassium dichromate titration were compared and analyzed for the content of active Al. The results show that the EDTA titration method based on microwave digestion can accurately determine the contents of Al， Al₂O₃， AlN， Fe₂O₃ and C in the condensed phase combustion products of composite propellants. Microwave digestion can effectively dissolve the Al₂O₃ shell coating on the surface of active Al. The optimal parameters of microwave digestion is supposed to be V_H3PO4∶V_H2SO4∶V_HNO3=10∶2∶1. The temperature was 240 ℃， and the digestion time was 150 min. ICP spectroscopy can also detect all component contents of condensed combustion products， with a precision slightly lower than EDTA titration. The content of active Al in condensed phase combustion products determined by gas volumetric method and potassium dichromate titration was significantly lower than that determined by EDTA titration and ICP spectrometric method. EDTA titration is the most accurate method to determine the content of active Al. Compared with gas volumetric method， potassium dichromate titration method and ICP spectrometric method， the accuracy of EDTA titration is improved by 60%， 40% and 22%， respectively.

Abstract:The tandem warhead with high-speed kinetic fragment and coated reactive material has both high-speed penetration and chemical energy damage effect. This paper is aimed to research its tandem damage effect on shielded charges. The impact dynamics model of impacting on shielded charges by the high-speed kinetic fragment and coated reactive material was established. By combining the excitation theory of reactive materials with the initiation criterion of shielded charges， the impact damage to the shielded charges by the high-speed kinetic fragment and coated reactive material was calculated and analyzed. Based on the 2D-Autodyn platform， the initiation process of shielded charges impacted by the high-speed kinetic fragment and coated reactive material was simulated. The comparison verifies the consistency between theoretical calculation and numerical simulation. By Combining theoretical analysis and numerical simulation results， the main influencing factors of the damage to shielded charges， the probable damage modes and the transition conditions between each damage mode were discussed. The results show that there are five damage modes for the shielded charges impacted by the high-speed kinetic fragment and coated reactive material ， including the forepart penetration initiation mode （Ⅰ）， the main part penetration initiation mode （Ⅱ）， the no reactive material reaction and no penetration initiation mode （III）， the reactive material reaction enhanced initiation mode （Ⅳ） and the reactive material reaction and no initiation mode （Ⅴ）. When the structure and material properties are determined， the main influencing factors of damage modes are the impact speed and shielding thickness. The theoretical model established in this paper can predict the above damage modes well.

Abstract:The dynamic energy release characteristics of the PTFE-based energetic liner are related to the damage effect of the jet to the target. In this paper， the dynamic overpressure of energetic and aluminum jets in a quasi-closed chamber was measured by static explosion test. The jet energy release and energy release efficiency were obtained by theoretical calculation. The results showed that the energetic liner underwent a deflagration reaction during the forming process， and the overpressure peak of the energetic jet can be increased by 3 times to 4 times compared with that of aluminum jet. For PTFE/Ti energetic liner， in the content range of 0% to 70%， as the tungsten content increased， the jet energy release decreased. But the energy release efficiency was improved due to the increased explosive driving load and the intensified friction between tungsten particles and active metals. For PTFE/Ti energetic liner， in the mass range of 13-30 g， as the mass of the liner increased， the jet energy release was improved. But the energy release efficiency dropped due to the decreased forming pressure of the penetrator.

Abstract:In order to obtain the damage characteristics of polytetrafluoroethylene/aluminum （PTFE/Al）， five PTFE/Al reactive liners with different Al particle sizes， by mold pressing and sintering， were prepared acting on double spacered plates . The results show that with the increase of Al particle size from 10 μm to 200 μm， the broken hole area， equivalent broken hole diameter ，broken hole uplift height and the volume of damaged area of steel and aluminum targets both decrease. When Al particle size is 10 μm， the damaged parameters of steel target are S_steel=0.4 CD （charge diameter）， h_steel=0.48 CD， V_steel=420 cm³， and the damaged parameters of aluminum target are S_aluminum=3.82 CD， h_aluminum=1.72 CD， V_aluminum=2280 cm³. PTFE/Al reactive jet with Al particle size 50 nm/70 μm can significantly improve the perforation effect of steel target， and d_steel=0.59 CD. Based on the experimental data， the analysis model of rupturing damage effect of reactive jet on behind-tagert is obtained by fitting.

Abstract:In order to obtain high energy density liquid propellant fuels and increase the payload of the launch vehicle， 20 different methyl-substituted bicyclobutyl derivatives were designed， and the influence of the structure of bicyclobutyl derivatives on performance was studied through theoretical calculations. Results show that with the increasing number of methyl substituents， the heat of formation and specific impulse of bicyclobutyl derivatives show a decreasing trend. When the substituent is para-substituted， its molecular stability is the best， and the heat of formation and specific impulse are larger， while the ortho-position substitution has a weakening effect on the heat of formation and specific impulse of bicyclobutyl derivatives. Among the designed compounds， the specific impulse of bicyclobutyl is the highest. When the mixing ratio of bicyclobutyl and liquid oxygen is 28.5∶71.5， the specific impulse can reach 304.52 s， and the main combustion products are CO（34.64%）， CO₂（13.89%） and H₂O （29.54%）. The comprehensive performance of all designed products is better than that of rocket kerosene. This study provides theoretical support for the design and synthesis of high-energy fuels.

Abstract:The thermal expansion characteristic of explosives under thermal stimulation affects the application of explosives. The thermal expansion characteristic of ［2，2′-bi（1，3，4-oxadiazole）］-5，5′-dinitramide （ICM-101） was studied by using in-situ X-ray powder diffraction， and the thermal expansion coefficient of ICM-101 was obtaind based on Rietveld structure refinement. Results show that there is reversible anisotropic under the high temperature expansion process of ICM-101. In the temperature range of 30-170 ℃， the thermal expansion coefficients of the unit cell parameters a， b， c axis and volume V are 9.19×10^-5 ℃^-1， -9.22×10^-6 ℃^-1， 5.21×10^-5 ℃^-1 and 13.8×10^-5 ℃^-1， respectively. The b-axis exhibits negative expansion characteristics. The unit cell stacking structure of ICM-101 at different temperatures and its correlation with thermal expansion characteristics were studied via the method of molecular spectroscopy technology combined with theoretical calculations. Results show that the compression deformation of the four-membered ring structures of ICM-101 molecules under thermal stimulation is an important reason for the linear negative expansion of the b-axis . Compared with other explosive crystals， the influence of unit cell packing on the thermal stability of explosive crystal structures were analyzed. The thermal expansion anisotropy of explosive crystals with strong hydrogen bonding layered stacked structure is more obvious. When the relative angle between molecules is greater than 100°， the intra-layer hydrogen bonding network affects the interlayer interaction. On the contrary， it will affect the a， b， and c axis directions and limit its thermal expansion.

Abstract:To improve the energy property and low vulnerability of cast HMX-Al based explosives， high solid -content aluminized PBX were designed by analyzing the influences of Al and HMX contents on detonation properties. A casted PBX GOL-42 of 90% solid content with HTPB/IPDI binder was manufactured by introducing desensitizers and process agents and was optimized by three-grade grain-size distribution. The GOL-42 explosive showed good processing and safety properties. The detonation property， low vulnerability， mechanical property， thermal property and accelerated storage property were measured by their corresponding standard test methods. The results showed that its measured density， detonation velocity， detonation pressure， Gurney coefficient of Φ25 mm cylinder test was 1.782 g·cm^-3， 8251 m·s^-1， 26.9 GPa， 2.76 mm·μs^-1， respectively. And in the low vulnerability examinations， including bullet impact test， slow cook-off test and fast cook-off test， all the reaction grades were combustion. Its estimated storage life was over 20 years. GOL-42 showed perfect overall properties and was predicted as a long-life low vulnerability cast explosive.

Abstract:High performance liquid chromatography （HPLC） has several advantages， such as high sensitivity， good reproducibility， high efficiency， and high automation. HPLC is widely used for purity analysis and quality monitoring of chemical materials. 2，4，8，10-Tetranitrobenzopyrido-1，3a，6，6a-tetraazapentalene （BPTAP） as a new heat-resistant explosive has received wide attentions in recent years. However， there is a lack of HPLC method for BPTAP at present. Thus， we investigated and optimized the chromatographic conditions of separating BPTAP， and established a HPLC method for the analysis of BPTAP purity. The method is based on a Plus C18 column （4.6×150 mm， 5.0 µm） by using the mixture of acetonitrile and water （containing 0.1 mg·mL^-1 ammonium acetate） as the mobile phase. Gradient elution mode was used with the detection wavelength at 230 nm. The retention time of BPTAP is 9.13 min with good resolution of all peaks （greater than 1.90）. The method was further verified， and it is found that BPTAP has a good linear relationship between 0.5 µg·mL^-1 and 200 µg·mL^-1 with correlation coefficient （R²） of 0.9997. The detection limit and quantification limit are 0.02 µg·mL^-1 and 0.07 µg·mL^-1， respectively. In addition， the method was used for the purity analysis of BPTAP after the recrystallization， and it is proved that this method has good performance for the analysis of BPTAP.

Abstract:Burning damage technology is an important research area in energetic materials and damage. The research in burning damage technology was mainly reviewed and summarized from three aspects： the formulation design and application of incendiary agents， the damage theory and technology of burning thermal radiation， and the burning damage assessment technology. Problems such as insufficient burning damage effectiveness of incendiary agents， single process of parameter characterization in thermal radiation model and incomprehensive burning damage assessment method were pointed out. The future research emphases on burning damage technology include incendiary materials with high densities and high calorific values，the structure-effect relationship of incendiary agent charges，testing technology for key model parameters represented by the fireball temperature， correction and optimization of thermal radiation damage models， and the accurate assessment method of thermal radiation damage effect under the coupling effect of multiple damage elements in the damage field.

Abstract:ResoDyn Acoustic Mixers Incorporation developed a mixing technique known as Resonant Acoustic® Mixing （RAM） in the early 21st century. This technology uses acoustic waves to create multiple micro-mixing zones within a material rather than the bulk mixing generated by traditional impeller or rotor agitation or planetary mixer. RAM technology can be used for the large-scale production of pharmaceuticals， cosmetics， and bulk powder mixing. For energetic materials， RAM is considered to have potential advantages over traditional high-shear processing methods （e.g. planetary mixing）， including shorter time scales， improved mix homogeneity， reduced waste output， absence of moving parts （an ignition source）， and the potential to mix higher viscosity， ‘unmixable’ compositions （compared to planetary mixers）. RAM has become the processing technology of choice in the development and production of propellants， explosives， and pyrotechnics. A summary of applications of RAM in the field of energetic materials， including the formation of co-crystal explosives and nano thermites and the processing of propellants and PBXs， is detailly overviewed in this text.