CMDB Propellants Research Articles

Exploration of TKX-50-M (M=Pb, Bi and Cu) as insensitive high-energy combustion catalysts of HMX-CMDB propellant

In order to deal with the long-standing contradiction between safety and performance for propellent combustion catalyst, the TKX-50-M (M=Pb, Bi and Cu) were designed, synthesized and characterized. The density, thermal decomposition, mechanical sensitivity and energy performance of the prepared TKX-50-M were studied systemically. By taking NTO-Pb as the benchmark, the TKX-50-M exhibited much better energetic and safety properties. Besides, the combination of TKX-50-Pb, TKX-50-Cu and carbon black is conductive to the combustion of HMX-CMDB propellant. The burning rate of HMX-CMDB propellant increases from 16.80 to 21.28 mm s−1 at 20 MPa, and the pressure index reduces from 0.87 to 0.39 in the pressure range of 10–20 MPa. The catalytic mechanism of TKX-50-M were explored according to the results of combustion wave structure, flame image and characteristics of burning out surface. The catalytic effect of TKX-50-Pb is mainly reflected in the gas phase region, and the introduction of TKX-50-Cu and carbon black shows a significant synergistic catalytic effect. The results of this study not only help to explore insensitive high-energy combustion catalyst, but also helps to improve the combustion, energy and safety performance of CMDB propellants.

Analysis of the mechanical response of solid rocket engine propellant under acceleration shock

The increased-range solid rocket engine of new ammunition often needs to withstand extremely high acceleration overload, leading to damage to the propellant’s structural integrity. To address this issue, this paper constructs a nonlinear viscoelastic constitutive model for the CMDB propellant by using low- and high-strain rate mechanical property tests. Combined with the secondary development of explicit dynamics and numerical simulation technology, the mechanical response of a certain type of solid rocket propellant under different acceleration impacts is analyzed. The results show that under acceleration impact loads, the propellant will compress, rebound, and recover over time, continuously cycling. Its axial displacement, maximum equivalent stress, and maximum equivalent strain exhibit irregular sinusoidal wave-like periodic cycles. Looking at the time when the peaks appear, the time when the maximum equivalent stress appears always lags behind the time when the maximum axial displacement peak appears. Due to the viscous effect of the viscoelastic material of the propellant, the time when the equivalent strain peak appears will lag behind the equivalent stress. Because of the material’s damping effect, both the peak values of the maximum equivalent stress and equivalent strain decrease over time. Under continuous high acceleration impact loads, this viscous damping phenomenon continuously diminishes, and the peak value of the propellant’s axial displacement gradually increases.

Experimental study on self-heating phenomena of CMDB/HTPB propellant under intermediate strain rate compression load

Self-heating behaviour of solid propellants under intermediate strain rate compressive loading have been studied. Effects of two intermediate strain rate (1 s-1 and 150 s-1) of the CMDB/HTPB propellants were investigated. The compression test was conducted using a hydraulic testing machine and the self-heating temperatures were measured by an infrared camera. The results show the following: (1) For CMDB propellant, the surface temperature of specimens rapidly increased at the initial period, then decreased due to the movement of the high temperature region caused by deformation, and then increased again. Finally, the surface temperature slowly decreased due to heat transfer to the surroundings. Infrared thermography showed the formation of a hot spot. Cracks were initiated and gradually expanded to the interior area during compression. (2) For HTPB propellant, the surface temperature of specimens increased slightly. Compared with CMDB specimens, there was no significant damage to HTPB specimens. (3) For both CMDB and HTPB propellants, the temperature distribution of specimens was non-homogeneous. At the centre of the specimen surface, the temperature is the highest. The self-heating temperatures of propellant increased with increasing the strain rate. However, the difference is slight for HTPB propellant, whereas it is considerable for CMDB propellant.

Study on master curve of tensile strength of thermal aging composite modified double base propellant

In order to study the mechanical properties of thermal aging composite modified double-base propellant (CMDB), the tensile properties of CMDB propellant were investigated at four temperatures (323, 293, 273, 253 K) and different strain rates (3.3 × 10-5- 3.3 × 10-2 s−1). Uniaxial tensile tests were carried out on CMDB propellant samples with different aging time (0,10,20,35,50,65,80,100 d). The mechanical properties of CMDB propellant after aging were studied. The results show that the maximum tensile strength decreases with the aging time, and the strength value fluctuates within a certain range (Δσ<30 %). The master curve of the maximum tensile strength of CMDB propellant was obtained by using the time-temperature equivalence principle (TTSP), and the master curve equation of the aging strength was established. The equation can be used to predict the maximum tensile strength of CMDB propellant with different aging time in the range of quasi-static strain rate.

Effect of pre-fatigue on mechanical properties of modified double-base propellant

In this paper, fatigue tests of modified double-base propellant (CMDB) under cyclic loading under constant strain amplitude were carried out by using Dynamic Mechanical Analyser (DMA) at 20°C. The uniaxial tensile stress-strain curves at five strain rates after pre-fatigue were measured by a material universal testing machine, and the curves were similar to the uniaxial tensile test results of unfatigued propellant. The experimental results show that CMDB propellant has obvious strain rate correlation, and the initial elastic modulus and yield strength of the propellant increase with the increase of strain rate. The effect of prefatigue on the stress-strain behavior of CMDB propellant depends largely on the number of initial cycles and the strain stress loading amplitude. Under the initial cycle condition of pre-fatigue, the maximum tensile strength increases slightly with the increase of cycle number, while the elongation at break decreases with the increase of cycle number.

Thermal behavior and safeties of fine TAGzT and its CMDB propellants including characterization and energy performance evaluation

Thermal behavior and safeties of fine TAGzT and its CMDB propellants including characterization and energy performance evaluation

Improving ignition and combustion performance of Al@Ni in CMDB Propellants: Effect of nickel coating

Micron-sized aluminum particles tend to melt into agglomerates, leading to incomplete combustion, two-phase flow losses, and energy decrease of propellants. The higher ignition performance of core–shell Al@Ni makes it a promising candidate fuel with high combustion efficiency. However, little work has been done to study the combustion of Al@Ni in propellants. Here, we report a first attempt to investigate the combustion mechanism of core–shell Al@Ni in the double-based propellant containing high energy explosive HMX, and evaluate its potential as a fuel. Nickel in Al@Ni is determined to play a critical role during its intrinsic combustion and the combustion in propellants. In the condensed phase, the presence of Ni enhances the oxidation process by forming a porous oxide layer on the aluminum surface that promotes oxygen diffusion. Subsequently the phase transition and expansion of Ni break down this oxide layer, leading to the earlier ignition on the burning surface. Upon Al melting, the alloying of Ni and Al accelerates the volume expansion and surface tension reduction of the fuel, giving rise to vigorous melt-dispersion combustion and enhanced energy release. Enhanced thermal feedback and thermal decomposition exotherm combined to increase the burning rate of propellant. The resulting higher flame temperature allows the evaporation of small aluminum droplets into vapor to form smoke oxide productions, further reducing the size distribution of the condensed combustion products (CCPs). This study demonstrates the potential of Al@Ni as an effective fuel for double-based propellants, and provides the insight into its combustion mechanism in HMX-CMDB propellants, which is believed to be important for the development of novel aluminum-based fuels for solid propellants.

Mechanical Behaviors and Constitutive Relations under wide strain rate range for CMDB propellant

Propellant materials are occasionally experiencing severe dynamic loading during transporting and service process, thus their mechanical characteristics and potential mechanisms under transient loading are needed thoroughly understanding for its integrity designing and reliable service. The paper focuses on the mechanical behaviors of propellant CMDB, along with its potential mechanism and constitutive characterizations. Mechanical behaviors are firstly studied experimentally under strain rates from 0.0001 s−1 to 3800 s−1 using Instron mechanical device and Hopkinson bar apparatus. Strain-controlled experiments are also performed for specific focus on severe multiple loadings. It is found that CMDB presents high rate-dependence, and shares parallel mechanical behaviors under wide strain rates. So does the strain hardening ratio. The microstructural observation on crack maps demonstrates that the crack is rate-dependent too, which presents the increasing dimension and decreasing quantity with increasing strain rate. The mechanisms are accordingly proposed based on microstructures, which can explain reasonably the rate dependences. Finally, a constitutive equation is succinctly deduced to well capture the mechanic characteristics at large deformation under wide strain rate range, and the involved less parameters own the overwhelming merit in engineering simulation and applications.

Effect of Nano‐Copper Chromite on the Thermal Decomposition and Combustion of AP‐Based Solid Propellants

AbstractThis investigation was devoted to exploring the application performance of nano‐combustion catalyst CuCr2O4 in solid propellants. In this paper, raw CuCr2O4 and nano‐CuCr2O4 prepared by the mechanical grinding method were applied in solid propellants containing ammonium perchlorate (AP), which are ammonium perchlorate/ hydroxy‐terminated polybutadiene propellant (AP/HTPB) and ammonium perchlorate/composite modified double‐base propellant (AP/CMDB). And the scanning electron microscope, displacement volume method, thermogravimetric analysis, differential scanning calorimetry, and strand burner method were employed to characterize the performance of AP‐based solid propellants. The results show that the AP/HTPB propellant has fewer defects on the surface of it due to the presence of nano‐CuCr2O4, but it has no significant effect on the AP/CMDB propellant. Nano‐CuCr2O4 can also significantly increase the density of AP/HTPB propellant and AP/CMDB propellant to 1.736 g/cm3 and 1.633 g/cm3, respectively. Nano‐CuCr2O4 obviously advances the decomposition temperature of AP/HTPB propellant and AP/CMDB propellant, which also increases the apparent heat of decomposition. In addition, the burning rate of nano‐CuCr2O4‐AP/HTPB propellant and nano‐CuCr2O4‐AP/CMDB propellant increased to 1.60 mm/s and 3.23 mm/s, with an increase of 28.3 % and 26.3 %, respectively. Therefore, nano‐CuCr2O4 is expected to be widely used in solid propellants due to its excellent properties.

The Prediction of CMDB Propellant lifetime Based on Arrhenius accelerated model, Berthelot’s equation and Multi-step Prout-Tompkins Model

Different models were provided to predict the storage lifetime of propellants more accurately. The stabilizer was recognized as a vital parameter for double based propellants’ storage lifetime estimation. The stabilizer contents of a certain RDX-CMDB propellant were traced during the accelerated aging tests. Based on that, the safe storage lifetime of this propellant were predicted using the Berthelot’s equation, Arrhenius accelerated equation and the advanced kinetic model, respectively. The predicted results were compared and the causes were analysed. It found that the biggest disadvantage of Berthelot’s equation and Arrhenius accelerated equation is that the predicted results are significantly affected by the original data. In details, the minor difference of original data will bring tremendous errors when extrapolating to normal temperature. The general model which can be used to depict complex reactions adopted in AKTS software was preferred compared to reaction order (RO) model and Prout-Tompkins (PT) model.

Application of Nano‐Sized RDX in CMDB Propellant with High Solid Content

AbstractCompared to the ordinary RDX, nano‐sized RDX has many more excellent properties. Therefore two kinds of CMDB propellant were prepared for comparison. One is the normal CMDB propellant called M‐CMDB propellant, the other is N‐CMDB propellant which adds nano‐sized RDX to CMDB propellant. The morphology characterization, tensile properties, sensitivity, and combustion performance of the propellants were investigated, the results for N‐CMDB propellant were compared with that for the normal one. It has been found that the interface of N‐CMDB propellant showed no stratification and fewer overall defects than the normal one. The value of σm and ϵm for N‐CMDB propellant are increased by 32.6 % and 25.2 % at 323.15 K, respectively. At 293.15 K, the σm and ϵm values of N‐CMDB propellant also increased by 25.4 % and 46.9 % and increased by 17.5 % and 23.7 %, respectively, at 233.15 K. The friction and impact sensitivities of N‐CMDB propellant are decreased by 51.3 % and 50.4 %, respectively. The TG/DSC study indicated that, compared with M‐CMDB propellant, the thermal decomposition peak temperature of N‐CMDB propellant is advanced, and the apparent activation energy is reduced by about 6.0 % to 144.3 kJ ⋅ mol−1. Combustion performance measurements were carried out. It was observed that nano‐sized RDX is a good burning rate enhancer, because of the burning rate coefficient value of N‐CMDB propellant is relatedly increased by 36.9 %. Besides, the pressure exponent of N‐CMDB propellant is relatively decreased by 21.6 %. All the results indicate that the application of nano‐sized RDX will help to improve the comprehensive performance of CMDB propellant.

Preparation and Properties of a Flake Aluminum Powder in an Ammonium-Perchlorate-Based Composite Modified Double-Base Propellant

A flake aluminum powder (f-Al) is prepared by a bi-directional rotation mill method using a spherical aluminum powder (s-Al) as a raw material. Then, these two kinds of aluminum powders are used to prepare ammonium perchlorate-based composite modified double-base (AP-based CMDB) propellants. The properties of two kinds of AP-based CMDB propellants, such as the thermal decomposition performance, mechanical sensitivity, and combustion performance, are comprehensively researched. The results show that the exothermic peak temperature of the f-Al/AP-based CMDB propellant is lower than that of the s-Al/AP-based CMDB propellant. The impact and friction sensitivities of the propellant decrease by 12% and 187% after using f-Al to replace s-Al. In addition, the burning rate of the f-Al/AP-based CMDB propellant is 5.5% higher.

Preparation of Nano‐Spherical Cu‐en and Its Catalytic Study on the Performance of Solid Propellant

AbstractThis paper mainly describes a nano‐spherical energetic catalyst Cu‐en. The result of particle size distribution shows that the D50 value of Cu‐en is 80.18 nm. The thermal decomposition process of RDX, AP, and NC is improved obviously after mixed with Cu‐en. Among them, the change of AP is the most significant, and its peaks of high‐temperature decomposition and low‐temperature decomposition degenerate into one decomposition peak. The thermal decomposition temperature of NC also decreased from 214.5 °C to 191.6 °C. In the range of 3–9 MPa, Cu‐en can significantly increase the burning rate of HTPB propellant and reduce the pressure exponent n from 0.684 to 0.459. According to the test data results of the CMDB propellant, the nano‐spherical Cu‐en prepared by the spray drying method has a stronger catalytic ability than the micro‐nano Cu‐en prepared by the high‐energy ball milling method.

Reinforced combustion of the ZrH2-HMX-CMDB propellant: The critical role of hydrogen

Metal hydrides, which are capable of producing H2 and release much energy efficiently via combustion, are regarded as promising high-energy fuels for future advanced solid propellants. Here, we report our first attempt on the application of a high-density hydride ZrH2 in CMDB propellants containing the high-energy explosive HMX and the revelation of the combustion mechanism of ZrH2 in HMX-CMDB propellants. ZrH2 was found to be capable of enhancing the combustion of HMX-CMDB propellants effectively. Especially, hydrogen in ZrH2 was determined to play a critical role during both its intrinsic combustion and the combustion in propellants. Upon ignition, ZrH2 dehydrogenates to produce Zr and H2, followed by combustion of the decomposition products. Interestingly, H2 release results in particle fragmentation either, promoting the combustion of hydride. As for the combustion of propellant with ZrH2, in the condensed phases, the Hδ+-Hδ− interaction promotes the thermal decomposition of HMX, leading to enhanced reaction rates. The ZrH2 combustion in propellant also starts with the hydrogen-release process, followed by melting and combusting of the newly generated metallic Zr on the burning surface. Thus, the heat feedback is greatly reinforced and the reactions in the condensed phases are further speeded up. The other dehydrogenation product, H2, participates in the gaseous combustion reactions. The insights into the effects of metal hydrides on propellant combustion are believed to be of great importance for developing novel hydride fuels for solid propellants.

Application and Properties of Nano‐sized RDX in CMDB Propellant with Low Solid Content

AbstractComposite modified double‐base (CMDB) propellant, benefitting from the outstanding performances of high energy and low signature, has attracted increasing focus in the past decade. To improve the integrative performance, such as enhancing the mechanical property and decreasing the sensitivity, CMDB propellant with low solid content containing nano‐sized RDX has been prepared. The microstructure, mechanical properties, sensitivity and combustion performance of the prepared propellant are studied. Results have shown that the interface of the CMDB propellant contained nano‐sized RDX (N‐CMDB) is more compact and the internal defects are less than those of the CMDB propellant with micro‐sized RDX (M‐CMDB). Compared with the maximum tensile strength (σm) and the corresponding elongation at maximum tensile strength (ϵm) of M‐CMDB, the σm values of N‐CMDB are improved by 37.4 % at +50 °C, 27.5 % at +20 °C and 26.7 % at −40 °C, and the ϵm values are increased by 16.1 %, 19.4 % and 39.6 %, separately. Moreover, the friction and impact sensitivities of N‐CMDB propellant are decreased by 51.3 % and 50.4 %, respectively. In the range of 8–18 MPa, the combustion performance of N‐MCDB propellant has been demonstrated more attractive with higher burning rate coefficient (8.692→10.950) and lower pressure exponent (0.384→0.299). All these results lead us to believe that the usage of nano‐sized explosives will contribute to improve the comprehensive performance of CMDB propellants and promote their application in weapon system.

Effects of disordered microstructure and heat release on propagation of combustion front

AbstractNumerical experiments for diagnosis of combustion of actual heterogeneous systems are performed on a one-dimensional chain. The internal microstructure of actual heterogeneous systems is apriori unknown, various distributions like uniform, beta, and normal have been considered for distributing neighboring reaction cells. Two cases, for the nature of distribution of heat release of reaction cells are taken into account, one with identical heat release and the other with disordered heat release. Role of different random distributions in describing heterogeneous combustion process is established in present paper. Particularly, the normal distribution of arranging neighboring reaction cells has been found to be powerful methodology in explaining the combustion process of an actual heterogeneous system at higher ignition temperatures for both cases of distributing heat release. Validation of the developed model with the experimental data of combustion of the CMDB propellants, gasless Ti + xSi system, a...

Modeling the Burning Rate of Heterogeneous Propellants over a Wide Range of Pressures

The variation of steady burning rate for heterogeneous propellants over a wide range of pressure is studied by experimental methods and theoretical analysis. Two kinds of heterogeneous propellants, GATo-1 CMDB propellant and 86 series composite propellant, are selected. An explanation for two inflection points observed in burning rate–pressure curve is presented. It is concluded that condensed-phase reaction dominates the burning process in the low-pressure region, which presents a low-pressure exponent, whereas heat feedback from the gas phase predominates in the high-pressure region with a high-pressure exponent. In the medium-pressure region, these two factors influence the burning process cooperatively and pressure exponent reduces first and then rises. Results calculated from the model show good agreement with experimental data. Thermal parameters analysis indicate burning rate is more sensitive to thermal conductivity of condensed phase, activation energy of condensed phase, specific heat capacity, and delay time of heat release of the condensed-phase reaction in high pressures. This model is of significance in burning rate characteristics in high pressures and interior ballistic properties in solid-propellant impulsive microthruster.

Preparation, Characterization and Combustion Catalytic Action of Bismuth/Zirconium Gallate

Bismuth/zirconium gallate(Gal-BiZr) was synthesized from gallic acid,bismuth nitrate,and zirconyl nitrate firstly,and characterized by elemental analysis,X-ray fluorescence(XRF),and Fourier transform infrared(FTIR) spectroscopies.The thermal behavior and decomposition mechanism of Gal-BiZr in a temperature-programmed mode were investigated by thermogravimetric(TG) analysis,differential scanning colorimetry(DSC),and condensed phase thermolysis/FTIR techniques.The decomposition products of Gal-BiZr are Bi2O3,ZrO2,and C.Samples of propellants containing Gal-BiZr were prepared by extrusion technology,and the effect of Gal-BiZr on double-base(DB) propellant combustion properties was investigated.Gal-BiZr exhibits good catalytic behavior in the combustion of DB and Hexogeon(RDX)CMDB propellants.

Thermal decomposition behavior, kinetics, and thermal hazard evaluation of CMDB propellant containing CL-20 by microcalorimetry

The thermal decomposition behavior of composite modified double-base propellant containing hexanitrohexaazaisowurtzitane (CL-20/CMDB propellant) was studied by microcalorimetry. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The effect of different proportion of CL-20 to the thermal decomposition behavior, kinetics, and thermal hazard was investigated at the same time. The critical temperature of thermal explosion (Tb), the self acceleration decomposition temperature (TSADT), and the adiabatic decomposition temperature rise (ΔTad) were calculated to evaluate the thermal hazard of the CL-20/CMDB propellant. It shows that the CMDB propellant with 38% CL-20 has relative lower values of E and lgA, and with 18% CL-20 has the highest potential hazard.

Constant-volume combustion energy of the lead salts of 2HDNPPb and 4HDNPPb and their effect on combustion characteristics of RDX–CMDB propellant

The constant-volume combustion energies of the lead salts of 2-hydroxy-3,5-dinitropyridine (2HDNPPb) and 4-hydroxy-3,5-dinitropyridine (4HDNPPb), ΔUc (2HDNPPb(s) and 4HDNPP(s)), were determined as –4441.92±2.43 and –4515.74±1.92 kJ mol–1 , respectively, at 298.15 K. Their standard enthalpies of combustion, Δcm H θ(2HDNPPb(s) and 4HDNPPb(s), 298.15 K), and standard enthalpies of formation, Δrm H θ(2HDNPPb(s) and 4HDNPPb(s), 298.15 K) were as –4425.81±2.43, –4499.63±1.92 kJ mol–1 and –870.43±2.76, –796.65±2.32 kJ mol–1 , respectively. As two combustion catalysts, 2HDNPPb and 4HDNPPb can enhance the burning rate and reduce the pressure exponent of RDX–CMDB propellant.