Properties Of Propellant Research Articles

Comparative study on the rheological properties of cellulose acetate and double‐base propellant

AbstractCellulose acetate (CA) and nitrocellulose (NC) are both cellulose derivatives with similar chemical structure and physical properties, and CA are non‐flammable and biodegradable, so CA has been used as a safe substitute to NC for artillery propellant research. The ester functional groups of CA and NC are different, and there are other components in the propellant, so the rheological properties of CA and propellant can be different slightly. However, the comparative study of rheological properties between CA and propellant is rarely reported. In this paper, the rheological properties of CA and double‐base propellant (DP) in extrusion process was studied by in‐line slit rheometer. The results show that the power‐law model can describe the rheological properties of CA and DP well. The shear viscosity of CA and DP decreases gradually with the increase of solvent ratio, and when the solvent ratio of CA is 0.87 and that of DP is 0.34, the rheological properties of CA and DP are most similar. The Arrhenius equation can reflect the relationship between shear viscosity and temperature of CA and DP, and the viscous activation energy of CA is about 23.68 kJ/mol, while that of DP is about 7.38 kJ/mol. In general, the effect of temperature on the rheological properties of CA is stronger than that of DP.

Research on the Aging Properties of HTPB Propellant under Vacuum

The space environment has high vacuum, rapid temperature alternations and other extreme conditions, which can affect the energy, ignition rate and ignition performance of solid propellants in the space environment. In order to obtain the space aging performance of HTPB propellant, this paper investigates the aging performance of HTPB propellant in vacuum environment and compares it with atmospheric pressure, and analyses the oxidative cross-linking, degradation chain scission and “dehumidification” behaviour based on the mechanical properties, cross-sectional state and infrared spectra of propellant before and after aging. The research results show that the anhydrous environment under vacuum prevents the occurrence of the chain scission degradation of HTPB propellant, and HTPB propellant is basically only affected by the oxidative cross-linking reaction, where the reaction rate is slow. The mechanical properties show that the breaking strength increases slightly in the first stage, in the later stage of aging, the oxidative cross-linking reaction was intensified due to the decomposition of AP, and the breaking strength increased obviously compared with the initial value. Under the atmosphere, the HTPB propellant was mainly affected by oxidative cross-linking reaction in the early stage of aging, and the breaking strength increased. In the later stage of aging, due to the chain scission degradation of OA moisture absorption, the breaking strength showed an opposite trend and decreased. In addition, an obvious “dehumidification” phenomenon occurs inside the propellant after aging, which is more obvious under a vacuum.

Mechanical Compression Behaviour of "Green" Rocket Propellants

The issues related to mechanical resistance of solid rocket propellants, which can appear during storage or handling of the launching system, are considered to directly influence the burning performance. Thus, in this study, four new types of composite rocket propellants, based on an environmentally friendly oxidizer (phase-stabilized ammonium nitrate), a metallic fuel (aluminium), and a "green" polyurethane-based binder (synthesized from an oligomeric isocyanate and a blend of polyester-polyols obtained through the catalytic degradation of polyethylene terephthalate), were subjected to compression mechanical analysis in order to highlight the importance of the binder on the response given by the tested materials subjected to compressive loads. The samples showed remarkable mechanical performances, the experiments allowing us also to determine the influence of the binder composition and fuel granulation on mechanical properties of the composite propellant.

Experimental and numerical investigation of aluminum particle combustion driven instability in solid rocket motors

Aluminum particles are extensively employed to enhance the energetic properties of propellants. However, the heat release rate (HRR) fluctuations resulting from aluminum combustion can potentially affect the stability of solid rocket motors (SRMs). Using a self-made high-pressure combustion diagnostics system and laser ignition system, this work investigates the combustion behavior of single aluminum particle under propellant atmosphere and acoustic excitation. An unsteady aluminum combustion model using Ranz-Marshall correlation and involving the heat and mass transfer equation was developed. The D2 law of aluminum particle combustion in a real propellant under 0.5 MPa was fitted as t = D2/0.31. The measured combustion rate of laser-ignited aluminum particles was found to increase from 0.381mm2/s to 0.465 mm2/s when an acoustic excitation of sine wave(200 Hz, 20Pa) was applied to the propellant, which agreed well with the prediction of the proposed unsteady combustion model whose error was 4.7%. Then, the verified correlation was included in the SRM to calculate the HRR fluctuation of the aluminum on acoustic boundary near the propellant burning surface. The effects of particle diameter, gas velocity, oscillation amplitude and frequency on the HRR fluctuation were obtained. It was found that the HRR fluctuation increases with the increasing particle diameter, gas velocity, and oscillation amplitude, and that due to the acoustic boundary effect, the HRR fluctuation is more sensitive under low-frequency oscillation. Based on the HRR fluctuation of aluminum combustion and particle damping, the growth rate of instability resulting from aluminum combustion in an SRM was investigated. The results showed that the growth rate of instability resulting from aluminum combustion were 9.38s-1 and 24.06s-1, while the particle damping (−25.8s-1) caused by combustion residuals, which suggests the aluminum particles play a critical role in SRMs combustion instability.

Transmissive Mode Laser Micro-Ablation Performance of Ammonium Dinitramide-Based Liquid Propellant for Laser Micro-Thruster.

The transmissive mode laser micro-ablation performance of near-infrared (NIR) dye-optimized ammonium dinitramide (ADN)-based liquid propellant was investigated in laser plasma propulsion using a pulse YAG laser with 5 ns pulse width and 1064 nm wavelength. Miniature fiber optic near-infrared spectrometer, differential scanning calorimeter (DSC) and high-speed camera were used to study laser energy deposition, thermal analysis of ADN-based liquid propellants and the flow field evolution process, respectively. Experimental results indicate that two important factors, laser energy deposition efficiency and heat release from energetic liquid propellants, obviously affect the ablation performance. The results showed that the best ablation effect of 0.4 mL ADN solution dissolved in 0.6 mL dye solution (40%-AAD) liquid propellant was obtained with the ADN liquid propellant content increasing in the combustion chamber. Furthermore, adding 2% ammonium perchlorate (AP) solid powder gave rise to variations in the ablation volume and energetic properties of propellants, which enhanced the propellant enthalpy variable and burn rate. Based on the AP optimized laser ablation, the optimal single-pulse impulse (I)~9.8 μN·s, specific impulse (Isp)~234.9 s, impulse coupling coefficient (Cm)~62.43 dyne/W and energy factor (η)~71.2% were obtained in 200 µm scale combustion chamber. This work would enable further improvements in the small volume and high integration of liquid propellant laser micro-thruster.

Study on mechanical properties of solid propellant NEPE

AbstractNitrate ester plasticized polyether (NEPE) propellants, are high energy solid propellants that are used widely in solid rocket motor. It is necessary to study the mechanical properties of NEPE propellants in order to ensure an accurate prediction of the performance of solid rocket motors and ensure the safety of launch platforms.We studied the viscoelastic hyperelastic constitutive model of NEPE propellants. The speckle defocusing method and digital image correlation(DIC) method are used to obtain the strain of solid propellant NEPE in three directions during unidirectional stretching, and the volume change rate, Poisson's ratio and true strain curves of NEPE under different stretching rates are obtained. With the increase of loading rate, the maximum stress that NEPE can encounter increases, and the modulus at the initial elastic stage also increases. At the initial stage of stretching, the volume change rate is close to 1, the Poisson's ratio fluctuates within a range close to 0.5. When the engineering principal strain in the tensile direction reaches a certain value, the volume change rate begins to increase and the Poisson's ratio begins to decrease. The strain of solid propellant NEPE in three directions during uniaxial tension was successfully measured by speckle defocus method and digital image correlation (DIC) method. NEPE is close to being a super elastic material at the initial stage of stretching. The change trend of the volume change rate curve of different loading rates is consistent, and the stretching rate has no effect on the volume change rate of NEPE.

Creep properties and prediction model of composite solid propellant

In order to describe the creep properties of HTPB propellant, uniaxial tensile creep tests of propellant under different stresses were conducted. Based on the principle of viscoelastic theory, the Burgers model was used to describe the creep properties of the propellant. Combined with the experimental data, the parameters of Burgers model under different stresses were determined, and the model parameters were expressed as a function related to creep stress, and finally the model was verified by using the test data under creep stress 0.2 MPa. The results show that the Burgers model can describe the creep properties of the composite propellant well.

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.

Research on NEPE Propellant at High Strain Rates

In order to study the mechanical properties of Nitrate Ester Plasticized Polyether (NEPE) propellant at high strain rates, the impact tests of NEPE propellant were carried out by the split Hopkinson bar, and the stress-strain curves of NEPE propellant under different strain rates ( 1500s−1-4500s−1 ) were obtained. The test results show that NEPE propellant has obvious nonlinear elasticity and strain rate sensitivity. The microstructure of NEPE propellant was observed by scanning electron microscope, and the fracture mechanism of NEPE propellant under high strain rate was obtained by analyzing the microstructure of propellant. In this paper, a nonlinear visco-hyperelastic constitutive model is adopted, in which Rivlin model and the viscoelastic model are used to describe the mechanical properties of materials. The constitutive parameters of the material were obtained by fitting the test data, and it was proved that the model could well describe the mechanical properties of NEPE propellant at high strain rates by comparing the test curve under different strain rates.

Study on impact damage mechanism of gun propellant based on bonding contact model

As the main launch energy of barrel weapon, the dynamic mechanical properties of gun propellant is very important to evaluate the launch safety. Through the transverse drop hammer impact damage test at room temperature and the initial dynamic vivacity ratio test of the propellant, the crack growth law and the fracture degree of the damaged propellant were obtained separately. Based on the Hertz-Mindlin bonding contact model, the discrete element mechanical model of the rosette 19-hole gun propellant was established, and the transverse drop hammer impact damage simulation was carried out. The damage mechanism of the bonding contact model and the fracture degree of the damaged propellant were acquired, which were also verified by tests. The results show that the bonding contact model can accurately describe the impact damage law of propellant. The research results of this paper can be used to predict the abnormal chamber pressure caused by fracture of propellant, provides a research means for mechanical property evaluation of 3D printing gun propellant, and lays a theoretical foundation for quantitative evaluation of launch safety.

Correlation between the micro-structure and macroscopic mechanical properties of GAP-based propellant during aging

The correlation between the macroscopic mechanical properties and micro-structure of glycidyl azide polymer (GAP)-based solid propellants during aging has been studied. A typical 60 °C–180 d high-temperature accelerated aging experiment on propellants was conducted. The changes in micro-structure were analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscope (SEM), and component analysis of the plasticizer and stabilizer. Changes in the macroscopic properties were analyzed through uniaxial tensile tests. The experimental results indicated that the micro-structure aging mechanisms of the propellants were the chain breakage of crosslinking networks, decomposition of plasticizers, and dissolution of CL-20 particles. The macroscopic mechanical properties were characterized by a gradual decrease in the maximum tensile strength, maximum elongation, dewetting strain, and elastic modulus during the aging process. Through mesoscopic simulation methods and correlation analysis, the relationship between the macroscopic mechanical properties and micro-structure was further established. The macroscopic mechanical properties of propellants are effected by the coupling of microscopic aging mechanisms. Chain breakage of the crosslinking networks and decomposition of the plasticizers lead to a decrease in the elastic modulus of the binder matrix. The elastic modulus of the binder matrix effects the change in the elastic modulus of the propellant. The dissolution of the CL-20 particles results in a decrease in the interface strength. The interface strength mainly causes a decrease in the maximum tensile strength, maximum elongation, and dewetting strain. These results are important for developing reliable predictive aging models for GAP-based propellant.

Research on Propellant Performance Prediction Based on Neural Network or Algorithm Optimization

In order to analyze the four main properties of propellant, the performance prediction model based on BP neural network is established with LM algorithm and CG algorithm as the core algorithm, and the simulation calculation is carried out with the actual production process data and the performance of the model is analyzed. The results show that the mass prediction model based on BP neural network algorithm can quickly predict the properties of propellant. Compared with the prediction model based on CG algorithm, the prediction model based on LM algorithm is more suitable for propellant performance prediction and analysis.

Solid Rocket Propellant Photo-Polymerization with an In-House LED-UV Prototype

Composite solid propellants have used cast molding production technology for many decades, with intrinsic limitations on production flexibility, promptness, and grain geometry, as well as environmental implications on toxicity and global carbon footprint. This traditional method involves the use of toxic chemicals, has a long processing time, requires high temperature, and the products have limited geometries. To overcome those issues, different photo-curable resins have been evaluated as possible matrices. In fact, the UV-curing process is fast and has low energy consumption. The photocuring reaction parameters of six different pristine formulations were evaluated by Fourier transform infrared spectroscopy analysis. After finding the optimal curing parameters, different composites were prepared by adding 75 or 80 wt% ammonium sulfate particles used as an inert replacement for the oxidant. The thermomechanical properties and thermal resistance of the UV-cured composites were characterized via dynamic thermal-mechanical and thermogravimetric analysis. Subsequently, the mechanical properties of the inert propellants were investigated by tensile tests. The most promising resin systems for the production of solid rocket propellants were then 3D printed by an in-house developed illumination system and the obtained object micro-structure was evaluated by X-ray computed tomography.

Phase equilibria and interface properties of hydrocarbon propellant–oxygen mixtures in the transcritical regime

Vapor–liquid equilibria and fluid interface properties of binary mixtures containing either methane or cyclohexane representing fuel and nitrogen or oxygen are reported. The mixtures are studied at different temperatures and pressures, which are chosen such that the temperature of the fuel component is subcritical, while that of the gaseous component is mainly supercritical. Data are obtained from molecular dynamics (MD) simulation, as well as density functional theory and density gradient theory in combination with the PC-SAFT equation of state (EOS). The studied interface properties include surface tension, interface thickness, enrichment, and relative adsorption. Furthermore, bulk vapor–liquid equilibrium properties are computed with two distinct MD methods as well as the PC-SAFT EOS. All approaches are compared to data from highly accurate empirical EOS. Despite the fundamental differences between these methods, very good agreement between the results of MD, density functional theory, and density gradient theory and EOS data is observed for the phase equilibria and interface properties, reinforcing the present predictions. It is found that the equivalence of nitrogen to oxygen is rather limited, in particular for the methane propellant. The disparities are particularly pronounced for low temperatures, where the compositions of the bulk phases differ significantly. As a result, enthalpy of vaporization as well as surface tension attains much higher values for mixtures containing oxygen.

Molecular Simulation Study on the Aging Mechanism of NEPE Propellant Matrix

Polyethylene glycols (PEG) and toluene diisocyanate (TDI) are often used as the main components of binders and curing agents in solid propellants, and their aging is an important issue in the storage and use of propellants. To study the aging behavior and aging mechanism of nitrate ester plasticized polyether propellant (NEPE) matrix during storage, the transition states of aging reactions of binder and curing agent were optimized at the (U)B3LYP/6-311G(d,p) level of theory, and the rate coefficients over the temperature range of 298-1000 K were calculated by CVT theory. The results showed that there were five kinds of aging reactions for binder, which included decomposition, nitration, H abstraction, oxidation, and crosslinking reactions. Among them, theenergy barriers of oxidation and H abstraction reactions were relatively low (79.3-91.2 kJ·mol-1) and the main reaction types of binder aging. The main aging reaction of curing agent was decomposition. Compared with the aging reactions of binder, the energy barriers of curing agent are higher (196.6-282.7 kJ·mol-1) and the reaction is more difficult to occur. By comparing the energy barriers and rate constants of different reactions, it is found that the aging of NEPE propellant matrix can be divided into two stages. In the first stage, the propellant matrix mainly undergoes H abstraction and oxidation reaction, and as the reaction proceeds, the products crosslink to form -O-O-, -C-C-, and -C-O-C- bonds. At this time, the long chain molecules of the propellant matrix crosslink, and the molecular weight increases. This stage corresponds to the rising stage of mechanical properties in the aging process of the propellant. In the second stage, the propellant matrix mainly undergoes decomposition and nitration, resulting in degradation, the reduction of molecular weights, and the appearance of holes and microcracks in the matrix. This stage corresponds to the decline of mechanical properties in the aging process of the propellant. The above simulation results are in good agreement with the aging experimental phenomena, revealing the microscopic mechanism of the changes in the macroscopic properties of NEPE propellant during the aging process, and providing a theoretical basis for the related research on the aging properties and anti-aging technology of NEPE propellant.

Study on combustion properties of magnesium-rich propellant based on analysis of kneading mixture

In order to improve the combustion performance of the magnesium fuel, the heat value and combustion temperature of the mixture and the propellant were analyzed. The results show that: At the kneading machine speed of 1600 r/min, the magnesium and aluminum-rich fuel was prepared by adding propellant, with a calorific value of 2420 kg / t. The propellant has high calorific value, low combustion temperature, low non-combustible content, no by-products of combustion products, and low environmental pollution. Rich fuel shall meet the following requirements in use: First of all, the rich fuel should be added to the rich fuel to meet the combustion performance requirements; Secondly, to ensure that the mixing effect of rich fuel and mixture is consistent; Again, to ensure that the rich fuel does not produce harmful gases at higher temperatures. Rich fuels contain a variety of metal elements and trace elements (P / K), and their chemical composition is also different from traditional fuels such as coal and oil. According to the working principle and characteristics of the kneading machine, the type and added amount of rich fuel can be reasonably selected; At the same time, it can also consider the use of different metal elements and trace elements with different mixing amounts and different fuel composition, and reasonably choose the type and added amount of rich fuel.

Multi-scale simulation of diffusion behavior of deterrent in propellant

• 1 An onion model is introduced to simulate the diffusion of deterrent in the propellant. • 2 The gap between the experiments and simulation can be bridged by the onion model. • 3 A new time scale is found to describe the diffusion process in the crystalline polymer. • 4 The results of Raman spectra verify the correctness of the onion model. Concentration distribution of the deterrent in single-base propellant during the process of firing plays an important role in the ballistic properties of gun propellant in weapons. However, the diffusion coefficient calculated by molecular dynamics (MD) simulation is 6 orders of magnitude larger than the experimental values. Meanwhile, few simple and comprehensive theoretical models can explain the phenomenon and accurately predict the concentration distribution of the propellant. Herein, an onion model combining with MD simulation and finite element method of diffusion in propellants is introduced to bridge the gap between the experiments and simulations, and correctly predict the concentration distribution of deterrent. Furthermore, a new time scale is found to characterize the diffusion process. Finally, the time- and position-depended concentration distributions of dibutyl phthalate in nitrocellulose are measured by Raman spectroscopy to verify the correctness of the onion model. This work not only provides guidance for the design of the deterrent, but could be also extended to the diffusion of small molecules in polymer with different crystallinity.

Study of Energetic Materials of Double Base Propellant for Small Caliber Ammunition

Double Base Propellants (DBP) has been frequently utilized in the fields of rocket propellant and gun propellant. DBP has various advantages over conventional propellants, including easy formulation, high energy, and smokelessness. The research conducted in literature studies was applied by referring to the various energetic materials for DBP. The composition of a DBP consists of energetic raw material of Nitrocellulose (NC) and Nitroglycerin (NG). According to data analysis, NC can be manufactured from the raw material Nata de Coco, which has a nitrogen content of more than 12,5% in NC, which is in line with the levels of conventional military and propellant raw materials. Meanwhile, SMX (1,4-dinitrate-2,3-dinitro-2,3bis (nitratomethylene) butane) or GAP (Glycidyl Azide Polymer) on double-base propellants is suggested as potential alternative energy sources that can be utilized to substitute NG. The choice of new energetic material is influenced by the fact that Nata de Coco is abundant in Indonesia, while SMX and GAP in terms of manufacturing and handling are safety. The several parameters to characterize double-base propellants include thermal analysis, microstructure, surface area, burning rate value, and gaseous product. The results of thermal properties by DSC analysis on a DBP based on NC+NG+TiO2-trifluoroacrylate showed a change in exothermic decomposition at a temperature of 199.2oC. Meanwhile, TGA analysis of a DBP based on NC+NG+GAP showed mass decomposition at temperature 199,3oC. Furthermore, it was found that thermoplastic elastomers GAP have a significant effect on increasing the low-temperature mechanical properties of double-base propellants. As a result, the literature studies approach, which includes consideration of alternative energetic raw materials and characterization for double-base propellants, is the recommendation for obtaining superior performance double-base propellants with energetic materials.

Influence of Solid Filler on the Rheological Properties of Propellants Based on Energetic Thermoplastic Elastomer.

Glycidyl azide polymer-energetic thermoplastic elastomer propellant (GAP-ETPE) has high development prospects as a green solid propellant, although the preparation of GAP-ETPE with excellent performance is still a challenge. Focusing on the demand of high-strength solid propellants for free-loading rocket motors, a GAP-ETPE model propellant with excellent overall performance was prepared in this work, and the influence of adhesive structure characteristics on its fluidity was studied. Furthermore, the influence of filler on the rheological properties of the model propellant was investigated by introducing hexogen (RDX) and Al, and a corresponding two-phase model was established. The results may provide a reference for the structural design, molding process, and parameter selection of high-performance GAP-based green solid propellants.

Macroscopic and mesoscopic properties of HTPB propellant under low temperature dynamic biaxial compression loading

In order to study the macroscopic mechanical properties and meso damage mechanism of solid fuel hydroxy-terminated polybutadiene (HTPB) propellant under low temperature and dynamic biaxial compression loading, the INSTRON high strain rate hydraulic testing machine was used to carry out dynamic biaxial compression test of HTPB propellant in the temperature range of −50 °C ∼ -30 °C and the strain rate range of 1s−1–85s−1. Meanwhile, the control test at room temperature (25 °C) was set up, and microcomputed tomography (Micro-CT) was used to observe and quantitatively characterize the meso damage of the loaded specimens. The test results show that temperature and strain rate significantly affect the mechanical properties of HTPB propellant in biaxial compression, and the mechanical properties under biaxial compression loading are more susceptible to temperature than strain rate. In addition, there is a significant difference between uniaxial and biaxial strength under compression loading, and finally, the effect of temperature and strain rate on mechanical properties is closely related to the variation in properties and mesoscopic damage mechanisms of HTPB propellants. This paper can deepen researchers' understanding of the performance of composite solid propellant and other energetic materials at the macro and micro level, and provide more effective theoretical and technical support for accurate analysis of the grain structure integrity of airborne missile solid rocket motor (SRM) under low temperature ignition conditions.