Abstract:Addition of high energy boron into the liquid fuel is an effective method to improve the energy density of the blended fuel. However， the added content of boron is limited， due to the dramatic increase in the viscosity of the blended fuel. So it is important to increase the boron content as much as possible without obvious viscosity increase. Four organosilanes including propyltrimethoxysilane （C3-silane）， octyltrimethoxysilane （C8-silane）， dodecyltrimethoxysilane （C12-silane） and hexadecyltrimethoxysilanes （C16-silane） were used to modify boron particles. First， the modified boron particles were characterized by scanning electron microscopy， contact angle measurement， X-ray diffraction， particle size analysis （using dynamic laser scattering） and thermogravimetric analysis. Then the rheological properties of organosilane modified boron/JP-10 blend fuels were investigated. Finally， the effect of temperature on the apparent viscosities at different shear rates was studied. The results show that boric acid on the boron surface was removed upon surface modification with organosilanes and the surface characteristics of boron powder were transformed from hydrophilicity to hydrophobicity. The content of organosilane was less than 1.5% in the organosilane modified boron particles， which would have marginal effect on the total heat value. Organosilane modified boron/JP-10 blend fuels with solids content of 50% showed good fluidity and their apparent viscosities were lower than 0.3 Pa·s at 25 ℃ and 100 s^-1 of shear rate. Keeping other conditions the same， the apparent viscosity of blend fuels depends on the length of side chain alkyl group of organosilane： C3-silane>C8-silane≈C12-silane≈C16-silane. Organosilane modified boron/JP-10 blend fuels showed shear-thinning characteristics and the relationship between the apparent viscosity and the shear rate could be well fitted by power-law equation. The apparent viscosity of blend fuels depends strongly on the temperature and their relationship could be well expressed by Arrhenius equation. The shear activation energy of blend fuels increases with increasing the length of side chain alkyl group of organosilane coated on the boron.

Abstract:In order to obtain the gun propellant with progressive combustion characteristics and corresponding control methods at multi-dimensions， according to the principle of internal ballistics， the concept of the pre-grooved gun propellant was proposed. The physical and mathematical models of the combustion process were established， and the Г-Ψ relationship was deduced. The principle of progressive combustion and multi-dimensional control methods were demonstrated. The method used for the preparation of the pre-grooved gun propellant was described. The pre-grooved gun propellant structured with a center opening was designed， and propellants having different groove numbers and various length/outside diameter ratios were prepared. In order to compare with the seven-hole propellants with and without coating ， the combustion performance of the pre-grooved gun propellant was characterized by the closed bomb test. The experimental results show that the pre-grooved gun propellant has the progressive combustion behavior as theoretically designed. Compared with the seven-hole propellant， the combustion enhancement value（ΔL） value obtained by using this method is increased by 2 folds， the progressive combustion characteristic（L_m/L₀） value is increased by 24.4%， and the relative pressure at the split point（B_m） value is increased by 32.4%. The progressive combustion feature exhibited by pre-grooved gun propellants outperforms that of the seven-hole propellant， and was comparable to that of the coated seven-hole propellant.

Abstract:To improve the hazard classification of anhydrous hydrazine， the extremely insensitive detonating substance （EIDS） gap test and external fire test were conducted for the standard packaging anhydrous hydrazine （18 kg and 120 kg） in accordance with the United Nations “Recommendations on the Transport of Dangerous Goods， Manual of Tests and Criteria”. The deflagration process， the highest temperature of the fireball surface and shock wave effect of samples were obtained by a high-speed camera， an infrared thermal imaging and a shock wave pressure acquisition system. The experimental results show that， under external fire conditions， the TNT equivalence of the anhydrous hydrazine-18 kg was 0.724， which was 1930.67 times that of anhydrous hydrazine-120 kg. Under certain conditions， anhydrous hydrazine has obvious explosive properties and can be assigned to Division 1.1 C or Division 1.3 C for different packaging design pressures. The hazard class of anhydrous hydrazine is closely related to the standard packaging design pressure. For safety purposes， the design pressure of packaged anhydrous hydrazine should be properly reduced within the allowable range to effectively reduce its hazard.

Abstract:Aiming at the problem that the cohesive zone model parameters， describing the mechanical properties of the adhesive interface， which can′t be obtained by traditional experimental method accurately，the inversion research on the relevant parameters of bilinear cohesive zone model used for the adhesive interface is carried out by using the digital image correlation method and Hooke-Jeeves optimization algorithm based on the tensile test results of solid rocket motor rectangular adhesive specimens. The inversion results show that the maximum adhesive strength， modulus and failure fracture energy are 0.55 MPa， 0.57 MPa and 2.26 kJ·m^-2， respectively， when the tensile rate is 5 mm·min^-1. The relative error of simulated and measured stress-strain curves is corrected from 44.7% to 4.3%. When the tensile strain is 0.05 and 0.08， the maximum displacement errors of simulated and measured region of interest is 0.64 mm and 1.76 mm， respectively， and the average displacement errors of simulated and measured region of interest is 0.38 mm and 0.45 mm， respectively. The validation results indicate that the accuracy of the inversion identification method is high enough and the established cohesive zone model can be used to characterize the mechanical properties of the adhesive interface.

Abstract:The new challenge to the existing coating layer process was put forward by the development of solid rocket motor technology. In recent years， thermosetting resin as the matrix was used， combined with continuous automatic coating technology， the popular coating production method of coating layer lies in whether complete molding and excellent performance can be obtained quickly. The flow properties and casting condition of unsaturated polyester （UPR） coating layer were studied. The chemical rheological model of the UPR coating layer during continuous automatic manufacturing is obtained by introducing exponential function based on Kinua-Fontana model. The functional relationship of viscosity versus time and temperature of cured UPR is established. The suitable temperature for casting operation was obtained. The filling volume fraction distribution， flow rate distribution and weld line position of coating layer were predicted by introducing of POLYFLOW simulation software， which the constitutive equations is established on the base of Bird-Carrea power-law equation. The casting process was simulated at the constant rate and pressure， respectively. The results show that the casting temperature is below 35 ℃， the casting pressure is more than 1 MPa， and the inlet flow rate is more than 150 mm³·s^-1 and less than 175 mm³·s^-1 in the coating layer casting process.

Abstract:The aim of this study is to explore the effect of absorption coefficient on propulsion performance of the laser ablated ammonium dinitramide （ADN）-acetone based liquid propellant. ADN and absorbent were mixed with different proportions in the range of 0-80% and a proportional distance of 10% to form ADN-acetone based liquid propellants. The absorption coefficients of propellants with different proportions were measured and calculated using a near-infrared spectrometer. Under the laser energy of 60 mJ and liquid film thickness of 300 μm condition， the impulses generated by laser ablation of propellants with different proportions were measured using a high-precision torsion pendulum. Results show that the absorption coefficient decreased with the increase of ADN content. In addition， the impulse decreased after peaking at ADN content of 30%， but increased again at ADN content of 80% sharply. The decrease of impulse in the ADN content range of 30%-70% is mainly caused by the decrease of absorption coefficient which leads to the decrease of laser energy deposited by the propellant. The impulse increase at ADN content of 80% is caused by the propellant whose absorption coefficient approaches to 0 and constitutes a “water cannon target” with the container. After the container is ablated by the laser， the propellant will act as a constraint， and result in the increase of impulse.

Abstract:In order to prepare gun propellants with complex geometries， the extrusion 3D printing process of double base gun propellants was proposed. Square-shaped， wheel-shaped， star hole-shaped and lace seven hole double base gun propellants were printed by screw extrusion gun propellants 3D printer. The surface structure， size uniformity， density and mechanical property of the printed gun propellants were characterized. The results show that the surface of the printed gun propellants is smooth without obvious defects. The size uniformity of lace seven hole gun propellants reaches the standard of traditional gun propellant preparation process， and the size uniformity of arc thickness for wheel-shaped gun propellant is good， with a standard deviation of 0.026 mm and a relative standard deviation of 0.92%. The density of square-shaped gun propellant is higher （1.567 g·cm^-3） than those of other gun propellants （1.549-1.559 g·cm^-3）. The tensile strength of gun propellant samples with concentric filling path （the filling line direction is parallel to the tensile direction） and straight line （the filling line direction is perpendicular to the tensile direction） are 14.467 MPa and 10.789 MPa， respectively， the former is equivalent to that of gun propellants prepared by traditional extrusion process. The good printing of multi geometry gun propellants with radians and angles provides a basis for the preparation of complex geometry gun propellants.

Abstract:In order to solve the dilemma of traditional technology to prepare gun propellants with complex structure and explore a new way to improve incremental combustion surface of gun propellants， 3D direct ink-writing was used to design and print nitrocellulose-based gun propellants embedded with multi-cubic pores. The 3D printed nitrocellulose-based gun propellants embedded with multi-cubic pores were characterized by constant volume combustion and internal ballistic properties. The results show that the printed nitrocellulose-based gun propellants embedded with multi-cubic pores， prepared by nitrocellulose， energetic plasticizer， and solvent as printing materials， are in accordance with the expected design of incremental combustion surface. Due to the influence of the diameter of printing needle， the ratio of dissolved cotton， the ratio of alcohol/acetone， and the speed of solvent volatilization， there is a certain deviation between design size and actual size of printed gun propellants. The preliminary ballistic test of 12.7 mm machine gun shows that when the mixed charge of NC-120 and D-4/7 is 16 g and the charge ratio is 1∶1， the bore pressure is 314.2 MPa and the muzzle velocity is 854.1 m·s^-1. The stable and normal combustion of the direct ink-writing printed gun propellants embedded with multi-cubic pores in the chamber is realized. However， for the sake of practical application of printed gun propellants embedded with multi-cubic pores， several parameters need to be further optimized such as shape， web size， and the web size matching between inner and outer layer.

Abstract:In order to study the performance of aluminum-based composite fuel in NEPE solid propellant， the aluminum-base composite fuel（Al@AP） was used in the NEPE solid propellant instead of aluminum powder， and the effects of Al@AP on the combustion， mechanics， and process performance of NEPE propellant were studied by explosion heat test， engine test， residual active aluminum test， high-speed photography， unidirectional tensile test and process properties test. And the combustion mechanism of Al@AP in NEPE propellant was derived. Results shows that by replacing FLQT-3 Al powder with 19.5% Al@AP， the explosion heat of NEPE propellant increased from 6029.4 J·g^-1 to 6924.8 J·g^-1， and the mass of residue decreased from 28.91 g to 7.64 g， and the active aluminum content of residue decreased from 14.64% to 0.37%， and the particle size of residue decreased from 94.12 μm to 24.21 μm. The injection efficiency of NEPE propellant with Al@AP is improved. The residence time of aluminum powder at the burning surface decreased from 55 ms to 40 ms， and there was no obvious agglomeration phenomenon. Al@AP powder has little effect on the dynamic burning rate， mechanics and process properties of NEPE propellant.

Abstract:The bonding interface of solid rocket motor will be damaged due to the creep effect from long-term vertical storage. This paper reviews the relevant research progress from three perspectives as the influencing factors of interface damage under creep condition， interface damage test， and numerical simulation of interface damage. It emphasizes that the cumulative damage of bonding interface under creep condition cannot be ignored， summarizes the shortcomings of test and numerical simulation research， and makes a prospect. According to the findings， the most difficult aspect of experimental research is devising reasonable tests and selecting variables that effectively characterize the timeliness of damage. The focus of numerical simulation research is to build a creep interface cohesion model with damage， in order to provide some reference for the performance evaluation of bonding interface under storage conditions.

Abstract:The ignition and combustion characteristics of NEPE propellant were studied based on a CO₂ laser ignition test platform established， in which the combustion processes of NEPE propellant in different gas environments were photographed using a high-speed camera and the ignition delay times of NEPE propellant were measured under the pressure of 0.1-3.0 MPa in nitrogen and air through a signal acquisition system. The results show that the ambient pressure and gas environment strongly affect the ignition and combustion process of NEPE propellant. The combustion of NEPE propellant becomes more intense as the increase of ambient pressure， and the burning of NEPE propellant appears more violent in air as compared to that in nitrogen. The ignition delay time of NEPE propellant decreases with the ambient pressure increases in the range of 0.1 MPa to 3.0 MPa. Specifically， the reduction in ignition delay time of NEPE propellant is observed from 0.51 s to 0.29 s in nitrogen and from 0.32 s to 0.18 s in air. However， when the ambient pressure exceeds 0.5 MPa， the influence of the ambient pressure on the ignition delay time becomes insignificant. In addition， the burning rate of NEPE propellant is also found to be effectively affected by the ambient pressure. With the ambient pressure increases from 0.1 MPa to 3.0 MPa， the enhancement in burning rate of NEPE propellant can be seen from 1.71 mm·s^-1 to 4.54 mm·s^-1 in nitrogen and from 2.51 mm·s^-1 to 11.4 mm·s^-1 in air， and thus a stronger increase in the burning rate is observed in air. Finally， the experimental data of burning rate were fitted by an empirical formula， which indicates the Vielle burning rate formula is more suitable for reproducing the burning rate characteristics of NEPE propellant especially at 0.1-3.0 MPa.

Abstract:The Arrhenius equation has been widely used as kinetics model for predicating aging property and shelf life of polymer materials by extrapolating high temperature accelerated test data. However， the suitability of the equation to composite solid propellants was questioned. Therefore the application history of the Arrhenius equation on aging of composite solid propellants has been reviewed. By combing the theoretical evolution process of Arrhenius equation， physical meaning of the equation parameters was clarified， and the misunderstanding on the equation was revealed. Theoretical analysis shows that only one of the two parameters （frequency factor and activation energy） is relative to temperature in the Arrhenius equation， and the parameters can be regarded as constants to solid propellants aged between the highest acceleration temperature allowed by current industry-standard and room temperature. The following conditions should be met to apply the Arrhenius equation： 1） it can be considered as the same aging mechanism in the range of temperatures involved in， 2） it has similar aging levels at the deadline of different acceleration temperatures， and 3） it has a parameter k with physical meaning of rate constant exactly. Mathematical models with logarithmic time are unsuitable to fit performance-time relationship， while those with logarithmic performance are suitable.

Abstract:As an energetic material， octogen（HMX） is widely used in solid propellants. While improving the energy performance of the propellant， it also changes the combustion process of the propellant. To study the effect of HMX content on the ignition， combustion， and agglomeration properties of propellant and its condensed phase combustion products （CCPs）， burning surface photography， laser ignition and collection of the CCPs were used for testing and studying typical AP/HTPB/Al/HMX propellants with HMX contents ranging 0%-10%. Results show that as the HMX content increases from 0 to 10%， the ignition delay time increases from 191 ms to 286 ms， and both the burning rate and pressure exponent of the propellent decreases. The volume average particle size of the CCPs increased from 48.1 μm to 138.3 μm. The propellent with 10% HMX has the highest agglomeration degree on the burning surface， while the propellent with 8% HMX has the highest active aluminum content in the CCPs.

Abstract:In order to improve the safety performance of potassium perchlorate （KClO₄）， KClO₄/ Silver （KClO₄/Ag） composite particles were prepared by chemical reaction of glucose and silver ammonia on the surface of KClO₄ particles. The particle morphology， phase composition， thermal decomposition temperature and mechanical sensitivity of the modified particles were analyzed by means of scanning electron microscope （SEM）， X-ray diffraction （XRD）， differential scanning calorimeter （DSC）， et al. The results show that KClO₄/Ag composite particles have obvious spherification effect， smooth surface and no obvious edges and corners. On the basis of retaining the original good stability and high decomposition temperature of KClO₄， it also has the characteristics of silver metal. Compared with the initial raw KClO₄， the mechanical sensitivity of KClO₄/Ag composite particles decreased significantly， the friction sensitivity explosion probability decreased from 90% to 50%， and the impact sensitivity explosion probability decreased from 70% to 40%. At the same time， the thermal decomposition performance of KClO₄/Ag composite particles is obviously different from that of raw KClO₄. The exothermic peak of KClO₄/Ag composite particles is 12 ℃ earlier and the decomposition efficiency is higher than that of raw KClO₄.

Abstract:To study the mechanical properties of Hydroxyl-Terminated Polybutadience （HTPB） propellant/liner bonding interface for solid rocket motor at different temperatures accurately， the model-Ⅰ fracture properties of the interface were studied with experimental method and simulation. Firstly， the load-displacement curves of the test samples at different temperatures were obtained through uniaxial tensile tests and the failure process of the samples were also recorded with the high-speed cameras. It was found that the failure form of HTPB propellant/liner interface was cohesive failure of HTPB propellant， which indicated that the strength of bonding interface was higher than that of the propellant. From -40 ℃ to 60 ℃， the critical displacement first increased and then decreased， indicating that the effect of temperature on this parameter is obvious. And then a cohesion model with polynomial damage variable was developed， based on the bilinear cohesion law. According to the simulation data， the effects of the interface parameters on the predicted results of the interface properties at different temperatures were analyzed. Moreover， the load-displacement curves of the bonding interface at different temperatures were predicted with the critical displacement as a known parameter. It found that the predicted results by simulation were in agreement with the experimental results， which indicates that the developed interface model can more accurately reflect the temperature-dependent behavior of model-Ⅰfracture of the debonding interface for solid rocket motor than the bilinear cohesion model.

Abstract:In order to realize the non-destructive measurement when predicting the storage life of nitrate ester plasticized polyether （NEPE） propellant， the high temperature accelerated aging， gas content monitoring and uniaxial tensile mechanical property experiment were carried out on NEPE propellant with 10% constant compression strain . The non-destructive storage life prediction model based on characteristic gas contents was proposed through correlation analysis and remaining life prediction model. The results show that during the storage and aging processes， the total amount of CO gas is the largest， reaching more than 1300 mg at different temperatures. The generating rates of NO and CO are growing slowly in the early aging period， and growing faster in the late period. The generating rate of HCl increases rapidly during the eraly and late aging period and slowly in the middle. Maximum tensile strength σ_m and maximum elongation ε_m increase slightly in the early aging period， the former oscillates slightly and the latter gradually increases in the middle period， and both of them decrease sharply in the late period. The correlation between the contents of CO and the maximum tensile strength is largest and there is a single correlation between them at different temperatures. The maximum correlation value reaches about 0.93-0.95. Four life prediction methods of NEPE propellant are established based on traditional and improved aging life prediction model， tensile strength and CO content. The maximum correlation coefficient and estimation results show that the improved prediction model based on the content of CO gas release is most effective.

Abstract:Slow cook-off test is one of the key tests of low vulnerability assessment for solid rocket motor. In order to study the influence of the charge size of HTPB composite propellant on the slow cook-off characteristics， slow cook-off tests and numerical simulation were carried out to compare and analyze the ignition growth laws of solid rocket motor under slow cook-off tests， with charge dimensions of Φ100 mm × 200 mm， Φ160 mm × 400 mm and Φ522 mm × 887 mm. Their corresponding ignition temperatures， ignition positions and response levels were determined. Results show that the ignition temperature of specimens of Ф100 mm×200 mm， Ф160 mm×400 mm and Ф522 mm×887 mm of solid rocket motors are 244 ℃， 172 ℃ and 155 ℃， respectively. Taking test data as inputs， the calculated ignition temperature is 250， 269， 154℃， and their corresponding calculation errors and response levelsare 2.88%， 1.17%， 0.64%， and explosion， explosion and deflagration. The calculated cloud diagram shows that the ignition position of medium and small test pieces is located in the center of charge cylinders， and the ignition position of full-scale solid motor is in the center of meat thickness of solid propellant front-end， which is a ring shape area.

Abstract:In order to realize the efficient application of TKX-50 in field of solid propellants， the energy performance of poly（glycidylaminopropyl ether） （GAP）-based solid propellants containing TKX-50， CL-20， and TKX-50/CL-20 was calculated using the minimum free energy method， and the feasibility of TKX-50 and CL-20 combination application was analyzed. The application efficiency of TKX-50/CL-20/GAP-based solid propellant was also estimated. The results show that when TKX-50 content increases， balance combustion temperature of propellant in combustion chamber（T_c） and combustion gas average relative molecular mass（） of propellant decrease at the same time， and the theoretical ratio of impulse was first increased and then decreased. The compatibility of TKX-50 and CL-20 was moderate compatibility. It has good thermal stability and safety performance of the TKX-50/CL-20 mixture propellant. It can significantly broaden the choice of the content of each component of the formulation with TKX-50/CL-20 mixture propellant. The lower limit of CL-20 content in the compound propellant with theoretical specific impulse greater than 272 s was only 40% of pure CL-20 propellant. At the same energy level， TKX-50/CL-20 mixture has the characteristics of low cost and low characteristic signal， and has the potential of engineering application.

Abstract:To investigate the quasi-static tensile mechanical properties of aging high solid content modified double-base propellants （CMDB）， the uniaxial tensile tests of CMDB propellant were carried out at four different temperatures （323， 293， 273， 253 K） and different strain rates （3.3×10^-5， 3.3×10^-4， 3.3×10^-3， 3.3×10^-2 s^-1）. The CMDB propellant samples with different aging time （0，10，20，35，50，65，80，100 d） were tested by gas chromatography. The mechanical properties of CMDB propellant and the change of stabilizer content after aging were studied. The results show that the maximum elongation and the content of stabilizer decrease significantly during the aging process， which can be used as the failure criterion of the aging CMDB propellant. By using the time-temperature superposition principle （TTSP）， the maximum tensile strength curve of CMDB propellant was obtained， and the aging strength main curve equation was established， which could be used to predict the maximum tensile strength of CMDB propellant with different aging time in the range of quasi-static strain rate.

Abstract:In order to study the problem of impact strength and rheological properties of propellant substitutes （Cellulose Acetate， CA） assisted with supercritical carbon dioxide （SC-CO₂）， the in-line slit rheometer， drop hammer impact test machine， SEM were used， and the rheological properties， impact strength and cell morphology of product were characterized in varied experiment conditions. Research results prove that， when process temperature is 50 ℃， solvent ration is 1.2 mL·g^-1， flowability of CA is optimized evidently as injection speed of CO₂ increasing. However， impact strength of extrusion product only account for nearly 53.11% of those products prepared without SC-CO₂（when injected mass fraction of SC-CO₂/CA is 0.173%， screw speed is 10 r·min^-1）； SEM results prove that， quantities of irregular foam structure exist in product prepared with SC-CO₂， foam size are both over 2 μm， some of them even reach at 15-25 μm. Impact strength and product appearance could be modified as screw speed increase， product prepared in 14 r·min^-1 attain higher impact strength （nearly 170.33%） than 6 r·min^-1. During the process of propellant substitutes assisted with supercritical carbon dioxide， rheological properties of CA in barrel could be optimized as injection speed， solvent ratio， process temperature and screw speed increase， however， impact strength of CA could be positively modified as screw speed increase.

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 study the damage and failure process of adhesive interface of solid rocket motor， rectangular adhesive specimen of solid rocket motor was made based on QJ2038.1A-2004 regulation standard and tensile tests was carried out. The damage and failure mode of the adhesive interface specimen was obtained. The parameter inverse identification method which is based on step inverse and Hooke-Jevees optimization algorithm was adopted. The relevant parameters of the bilinear cohesive model of mix mode at the propellant/liner/insulator interface were obtained and were applied into the numerical simulation of the damage and failure process of adhesive specimen in tensile tests. Results show that the main failure form of adhesive interface specimen is the debonding at the interface of the propellant/liner/insulator layer； the proposed parameter inverse identification method can obtain the interface parameters of solid rocket motors well. The initial modulus， maximum bonding strength and fracture energy of the propellant/liner/insulator layer of solid rocket motors are 0.86 MPa， 0.63 MPa and 3.13 kJ·m^-2 at tension speed of 2 mm·min^-1， respectively. The damage of the propellant/liner/insulation layer interface makes the increase rate of stress decrease with the tensile strain. The initiation interface crack at the tip of the artificial debonding layer and the expansion along the center of the specimen， and finally penetration of the bonded specimen is the main damage and failure mode of the adhesive specimen.

Abstract:In order to study the migration phenomenon of deterrent in double-base oblate spherical propellant during storage， micro-Roman technique was used to characterize the concentration distribution of dibutyl phthalate（DBP） and poly （neopentyl glycol adipate）（NA） in double-base oblate spherical propellant after accelerated aging； and the combustion performance of double-base oblate spherical propellant was tested by the closed bomb test. Results show that the concentration of DBP and NA changed exponentially from the surface to the inside in one-dimensional direction， which conformed to Fick"s second diffusion law. During the accelerated aging process， the migration of DBP in double-base oblate spherical propellant was bidirectional， the concentration gradient of deterrent decreased gradually， the diffusion depth increased， the peak position of concentration shifted inward， and the combustion performance of double-base oblate spherical propellant also gradually decreased. High temperature would aggravate the migration of deterrent. The progressive combustion characteristic values of double-base oblate spherical propellant samples aged at 65 ℃，75 ℃ and 85 ℃ for 10 days were 1.3351， 1.2917 and 1.1888， respectively. With the increase of temperature， the progressive combustion characteristic values of double-base oblate spherical propellant decreased. Under the same aging conditions， the anti-migration characteristics of NA was higher than that of DBP.

Abstract:As the diffusion and migration of the deterrents affect the service life of gun propellants during the storage period， the molecular dynamics simulation （MD simulation） was applied to compare the diffusion rate of the small molecule dibutyl phthalate （DBP） and polyneopentyl glycol adipate （NA） in gun propellants. Meanwhile， the effect of nitroglycerin （NG） content on the diffusion of DBP and NA in double base gun propellants was explored and the diffusion mechanism was analyzed. The results indicate that the diffusivity of DBP and NA in nitrocellulose （NC） is equivalent at 5 ℃ and the diffusion coefficients are both in the order of 10^-12 m²∙s^-1. The diffusion coefficients of DBP and NA are 1.88×10^-11 m²∙s^-1 and 7.57×10^-12 m²∙s^-1 at 65 ℃， respectively. The diffusion coefficients of DBP and NA are 3.42×10^-11 m²∙s^-1 and 1.11×10^-11 m²∙s^-1 at 85 ℃， respectively. At the same temperature， the order of the diffusion coefficient of the deterrents is DBP>NA， which shows that NA has better anti-migration properties， which are more prominent at high temperatures. Owing to the high temperature， the peak value reduces， thus weakening interaction between DBP， NA and NC， meanwhile， the fractional free volume of system increases， which is conducive to the diffusion of DBP and NA. The diffusion capacity of DBP and NA increases with the increase of NG content. Adding NG weakens the interaction between DBP， NA and NC， so DBP and NA move more actively and the diffusion ability increases. The molecular dynamics simulation method is used to study the diffusion properties of the deterrents in gun propellants， which provides important theoretical guidance for predicting the life of gun propellants.