High-energy Propellants Research Articles

Research on equation of state parameters for high-energy solid propellants based on improved cylinder test and particle swarm optimization

With the development of high energy solid propellants, it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles (UAVs) when transporting and using them in contemporary warfare. An electric probe-type cylinder test measured the displacement-time behavior of NEPE high-energy solid propellant, and the parameters of the Jones-Wilkins-Lee (JWL) equation of state (EOS) were derived using particle swarm optimization (PSO) with the Gurney energy model. Further, the parameters of JWL-Miller EOS, determined through AUTODYN simulations, were validated by comparing airburst process simulations with experimental overpressure data. The study established a method for determining EOS parameters of high-energy propellants, achieving a high degree of accuracy. The derived parameters ensure precise modeling of propellant behavior, offering a reliable foundation for future applications in solid rocket motor performance optimization and safety assessment.

Modeling method of random collision of ellipsoidal particles in mechanical simulation for high energy solid propellant

Abstract It is based on the molecular dynamics algorithm of elliptical optimization to establish a mesostructure model of oval particles of high-energy solid propellant considering gradation and controllable filling rate according to the mesostructure characteristics of high-energy solid propellant. The bilinear cohesion model was applied to describe the interface damage behavior and carry out the high-energy propellant tensile test at three rates. The rationality of the elliptical particle model has been verified between the comparison of the calculated results with the experimental results established to describe the micromechanical behavior of high-energy propellants, which is to reveal the mesoscopic damage law of high-energy solid propellant under different tensile rates in this paper.

Preparation of Polydopamine Functionalized HNIW Crystals and Application in Solid Propellants.

The application of hexanitrohexaazaisowurtzitane (HNIW) as an oxidizer in solid propellants aligns with the pursuit of high-energy materials. However, the phase transformation behavior and high impact sensitivity of HNIW are its limitations. Due to the strong adhesion and mild synthesis conditions, polydopamine (PDA) has been employed to modify HNIW. However, the method suffers from a slow coating process and a non-ideal coating effect under short reaction time. Herein, oxygen-accelerated dopamine in situ polymerization coating method was developed. It was found that oxygen not only reduced the coating time but also contributed to forming a dense and uniform PDA layer. HNIW@PDA coated in oxygen for 6 h exhibited the most favorable performance, with a delay of 20.8 °C in the phase transition temperature and a reduction of 145.45% in the impact sensitivity. The -OH groups on the surface of PDA enhanced the interaction between HNIW and polymer binders, resulting in a 20.36% reduction in the dewetting percentage. The lower content of PDA in HNIW@PDA (1.17%) resulted in minimal variation in the heat of explosion for HNIW@PDA-based HTPB propellant (6287 kJ/kg) in comparison to HNIW-based HTPB propellant (6297 kJ/kg). Hence, HNIW@PDA-based propellants are expected to offer an alternative with promising safety and mechanical performance compared to existing HNIW-based propellants, thus facilitating the application of HNIW in high-energy propellants. This work presents a low-cost method for efficiently inhibiting the phase transformation of polycrystalline explosives and reducing the impact sensitivity. It also offers a potential approach to enhance the interfacial interaction between nitro-containing explosives and polymer binders.

Effect of particle/matrix interface parameters on mechanical properties of high-energy propellant based on three-dimensional RVE model

Abstract For composite solid propellant, the interface is the medium to transfer the load between particles and matrix. Because there are a large number of particle/matrix interface layers in the propellant, the mechanical properties of the interface become an important factor affecting the macro-mechanical properties of the propellant. It is necessary to study the influence of different interface mechanical parameters on the mechanical properties of high-energy propellants. In this paper, the three-dimensional representative volume element (RVE) model of solid propellant is established, and the three-dimensional bilinear cohesion interface parameters are established for this model. The influence law of interface parameters on its mechanical properties is obtained through simulation research. The results show that both the interfacial strength and the maximum failure displacement of the interface affect the tensile strength of high-energy propellant, and the interfacial strength plays a leading role and is very significant.

Reduced erosion and its erosion reducing mechanism of gun propellants by octaphenylsilsesquioxane

Low erosion high-energy propellant is one of the research directions to extend the weapon's life and improve the weapon's capability. In this study, energetic propellants containing different corrosion inhibitors were designed and prepared. Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants. The mechanism of erosion-reducing of titanium dioxide (titania, TiO2), talc, and octaphenylsilsesquioxane (OPS) on the propellant was comparatively analyzed. The results show that OPS has the lowest burning rate and the longest burning time, and a minimized loss of fire force, with the best effect of explosion heat reduction. The erosion reduction efficiency of OPS is twice that of TiO2 and talc. The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion, and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO2 protective layer. This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.

Effects of Thermal Damage on Impact Response Characteristics of High-Energy Propellants.

Thermal damage due to microstructure changes will occur in propellants under thermal stimulation. It can significantly affect the sensitization, combustion, and other properties of the propellant, which, in turn, affects the impact safety of the solid propellant rocket engine. A new component which uniformly heats the sample was designed to conduct the Lagrange test and EFP impact test at different temperatures. The thermal decomposition and damage characteristics of the propellant during the heating process were quantitatively analyzed. Additionally, the effects of ambient temperature on impact initiation and detonation growth of the high-energy propellant were elucidated at a mesoscopic level. The results showed that the porosity of the specimen increased by 0.89% under the thermomechanical mechanism, which was mainly characterized by interfacial de-bonding between the AP and the binder. The increase in thermal damage changed the hot spot reaction rate and significantly affected the growth process of propellant impact initiation. A method was proposed to systematically calibrate the reaction rate model for the propellant at different temperatures. The theoretical model parameters of the high-energy propellant at two typical temperatures were calibrated in this way. The critical shell thicknesses computed using LS-DYNA, which, for 20 and 70 °C, were obtained as 15 and 20 mm, respectively.

ZrO2-reinforced polymer-matrix composites used for thermal protection systems of ultra-high temperature aerospace propulsion

Owing to the rapid development of high-energy propellants, the temperature of the solid rocket motor (SRM) combustion chamber has increased, necessitating the development of high-performance polymer matrix composites (PMCs) that meet the requirements of thermal protection systems (TPSs) for use in the ultra-high temperature combustion chamber. ZrO2 is an excellent and potential ultra-high temperature filler, the ablation properties of ZrO2-reinforced PMCs were investigated. ZrO2 reduced the ablation rate of the PMCs by up to 30.6 %. In order to optimize the design of ZrO2 filler, the reinforcement mechanism of ZrO2 on the ablation resistance of the PMCs was explained from the perspective of the properties and chemical reaction in the char layer. The results showed that ZrO2 can increase the residue rate and promote the densification of the char layer. In addition, ZrO2 promoted the formation of ZrC in the char layer, thereby improving the ablation resistance of the ZrO2-reinforced PMCs. The ZrO2-reinforced PMCs are expected to meet the requirements of the TPS used in the ultra-high temperature combustion chamber. Furthermore, the reinforcement mechanism of ZrO2 is conducive to the design of TPSs materials with excellent ablation performance and development of predictive models for the ablation performance of composites.

Study on meso-damage evolution process of high-energy propellant based on MCT

The complex microstructure of composite solid propellant makes the evolution of meso-damage very complicated during loading. It is always a hot issue to study the damage evolution law of propellant from the microscopic point of view.Based on the established tensile platform of MCT, the tensile test of high energy propellant specimens was carried out. The variation trend of internal porosity with the increase of tensile strain is obtained. It can be seen that during the drawing process, the internal porosity of high-energy propellant increases exponentially with the drawing rate.

AP assembled on ultrafine aluminum particle and its application to NEPE propellant

Coating modification is an important way to enhance the reactivity of aluminum powder. In this paper, ammonium perchlorate and aluminum powder were assembled into energetic microunits by liquid deposition method. Spherical particles with AP as shell and ultrafine aluminum powder as the core (Al@AP) were gained. The micromorphology results show that the coated particles are about 5 μm, and the coating layer is evenly distributed on the outer surface of aluminum powder, indicating a complete coating. The energetic microunits were implanted into the nitrate ester plasticizing adhesive system (NEPE) as solid phase fillers. The effect of filler on the rheological properties, safety, mechanical properties, thermal reaction and energy properties of the system was analyzed by comparing with the raw aluminum filler. The test results show that the rheological properties, mechanical properties and pressure index of NEPE containing system Al@AP meets the requirements of solid propellant charging. Compared with Al based propellant, the mechanical sensitivity and thermal sensitivity are decreased, the safety is better, and the explosion heat of the propellant is increased by 7.8%. The engine test shows that the specific impulse is increased by 1.2 s. Al@AP can improve the energy output and safety of NEPE propellant, and has potential application prospects in high-energy propellants.

Energy Applications of Ionic Liquids: Recent Developments and Future Prospects.

Ionic liquids (ILs) consisting entirely of ions exhibit many fascinating and tunable properties, making them promising functional materials for a large number of energy-related applications. For example, ILs have been employed as electrolytes for electrochemical energy storage and conversion, as heat transfer fluids and phase-change materials for thermal energy transfer and storage, as solvents and/or catalysts for CO2 capture, CO2 conversion, biomass treatment and biofuel extraction, and as high-energy propellants for aerospace applications. This paper provides an extensive overview on the various energy applications of ILs and offers some thinking and viewpoints on the current challenges and emerging opportunities in each area. The basic fundamentals (structures and properties) of ILs are first introduced. Then, motivations and successful applications of ILs in the energy field are concisely outlined. Later, a detailed review of recent representative works in each area is provided. For each application, the role of ILs and their associated benefits are elaborated. Research trends and insights into the selection of ILs to achieve improved performance are analyzed as well. Challenges and future opportunities are pointed out before the paper is concluded.

Experimental insight into interaction mechanism of guanidinium-5-aminotetrazole (GA) and nitrocellulose

5-Amino-1H-tetrazole (5-ATZ), an environmentally friendly energy-containing material for new propellants, is gradually applied in high-energy propellants and its ionic salt compounds have received wide attention. This study focused on investigating the interaction mechanism of guanidinium-5-aminotetrazole (GA) and nitrocellulose (NC) by kinetic methods and TG-DSC-FTIR analysis. DSC and TG experiments indicated that there was a certain interaction during the pyrolysis process of NC and GA. Comparing the kinetic models of NC and peak 3 in NC-GA, it can be found that the addition of GA mainly affected the m-value and contribution in the second step B→C, and the mechanism function changed from Fn to Cn,m. TG-DSC-FTIR experiments indicated that the initial decomposition product of NC, NO2, participated in the thermal decomposition process of GA, and the two reacted chemically to form CO, N2O, which made NO2 unable to completely oxidize the skeleton of NC to produce CH2O, HCOOH.

Morphology and Size Distribution of Condensed Combustion Products of Aluminum-Based Propellants

ABSTRACT Both glycidyl azide polymer (GAP) and hexanitrohexaazaisowurtzitane (CL-20) are high-energy compounds with very promising applications. However, there are relatively few relevant studies for GAP/CL-20 aluminum-based propellants. In this paper, the CCPs of aluminum-based GAP/CL-20 propellant under different operating conditions were collected by a gas collecting device, and the physicochemical properties of CCPs were carefully studied by various modern analytical and testing instruments. The results show that the CCPs consist mainly of smoke oxide particles (~1 μm), residual oxide particles (~20 μm) and agglomerates. Residual oxide particles are widely available, but have received less attention from researchers. The agglomerates can be divided into two categories: sphere-like agglomerates and non-spherical agglomerates. Sphere-like agglomerates include cracked spheres, solid spheres, hollow spheres, and spheres with oxide caps. Surprisingly, we found an agglomerate with two caps. Non-spherical agglomerates are larger in size than sphere-like agglomerates, and the non-spherical agglomerates include irregular agglomerates, coral-like aggregates, and filamentous agglomerates. As far as we know, coral-like aggregates and filamentous agglomerates in CCPs have not been reported in the literature. Pocket theory and inter-pocket bridge theory were used to explain the formation mechanism of fine filament agglomerates. In addition, the formation mechanisms of different types of agglomerates were analyzed and sorted out. The particle size distribution of CCPs at different pressures shows that the average particle size of CCPs decreases with increasing pressure. It is hoped that this paper can provide a reference for the design of high-energy propellant formulations.

Effect of micron-sized zirconium powder on combustion decomposition behavior of molecular perovskite energetic material DAP-4

Micron-sized zirconium (μZr) is a viable alternative fuel source for high-energy propellants. To explore the combustion performance of Zr-containing DAP-4-based composites, DAP-4/Zr and F/DAP-4/Zr composites were designed. The results showed that the optimized composite had high combustion performance. When DAP-4/Zr was 54:46, the sample had the highest combustion heat and the fastest flame spreading velocity. The combustion time of F/DAP-4/Zr became longer after adding F2602, and the flame spread was the fastest when F/DAP-4/Zr was 10:48.6:41.4. The results indicate that the introduction of μZr as a fuel in DAP-4 can improve the material's energy density and combustion characteristics.

Study on erosion-reducing additives and erosion inhibition principle for R2 high energy propellant

In view of the serious erosion problem of the gun barrel with the R2 high-energy propellant, an erosion tube device method was adopted, and silane organic substances, silicate inorganic substances, titanium dioxide nanoparticles and paraffin wax were selected as erosion-reducing additives. The effect of different erosion-reducing additives on the erosive property of R2 propellant was investigated by means of external addition. The erosion inhibition principle was also briefly investigated by scanning electron microscope and energy dispersive X-ray spectroscopy. The results show that paraffin wax has excellent ability to improve gun barrel erosion resistance, the erosion-reducing efficiency can reach up to 31.2%, the erosion-reducing efficiency of silanes is the next most effective, and silicate is poor.

Investigation of high rate mechanical flow followed by ignition for high-energy propellant under dynamic extrusion loading

Investigating the ignition response of nitrate ester plasticized polyether (NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident stimulus. Secondly, evaluates the risk of a shell crevice in a solid rocket motor (SRM) under a falling or overturning scene. In the present study, an innovative visual crevice extrusion experiment is designed using a drop-weight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. Based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.

Effects of Ammonium Perchlorate and CL-20 on Agglomeration Characteristics of Solid High-Energy Propellants

Energy density, which is an important indicator of the performance of solid propellants, is known to increase with the addition of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). However, it remains unclear how CL-20 affects the decomposition of ammonium perchlorate (AP) and energy release. Here, the effects of CL-20 on the combustion performance and agglomeration of propellants were investigated. The addition of CL-20 decreased AP decomposition temperature and the energy required for the transformation of AP crystals from orthorhombic to cubic. The burning rate and pressure exponent of the propellant with 42% CL-20 were significantly higher than those of the propellant containing 20% CL-20. Thus, adding CL-20 to the propellant improves the energy characteristics and burning rate and the pressure exponent increases. At low combustion chamber pressure, the agglomeration of the propellant containing a high content of CL-20 will be blown away from the combustion surface only after staying on that surface for a short time. In this process, the probability of volume growth of the agglomeration after merging with other agglomerations greatly decreases, thus reducing the overall agglomerate particle sizes; further, the addition of a small amount of CL-20 to the propellant may lead to a reduction in agglomerate particle sizes. AP with a smaller particle size weakens the agglomeration in the combustion process and decreases the number of agglomerates with large particle sizes. These findings lay the foundation for the development of novel high-energy propellants.

Impact-induced deformation and ignition related to localized viscous shear flow heating for high-ductility composite energetic materials

Understanding the impact-induced deformation and ignition properties of high-ductility composite energetic material (CEM), including high-energy propellants and casted high explosives, is fundamental to the safety design and usage of rockets and warheads and has been a broad concern in the fields of aerospace and defence. In this study, an impact ignition experiment is designed using a Split Hopkinson Pressure Bar to quantitate the continuum deformation and reaction responses of a high-ductility CEM sample undergone periodic impact loading pulses. The relation between macroscopic shear deformation rate and localized viscous shear flow heating, melting, and reaction is further investigated utilizing a macro-mesoscopic thermomechanical model. The results show that CEM sample is severely crushed to 2% of the original thickness and laterally extruded with a high shear rate (∼105 s−1). High shear deformation rate contributes to the localized viscous shear flow heating, thereby inducing temperature rise spike (∼200 K) and following ignition. Ignition of CEM sample occurs in the third compression pulse because the thinner sample exhibits a high velocity gradient, which causes a high viscous shear flow heating rate.

Theoretical study on the stability mechanism of a high energy system composed of molecules containing C[sbnd]O[sbnd]C or –N3 groups and aluminum hydride

The stability of aluminum hydride(AlH3) based high-energy propellants is important for its large-scale application. In this work, to explore the stability mechanism of systems composed of AlH3 and a binder containing COC or –N3 groups, molecular dynamics simulations were carried out to explore the thermal expansion properties of AlH3, and density functional theory calculations were employed to study the micro-interactions between molecules containing COC or –N3 groups and AlH3. More specifically, CH3OC2H5 and CH3N3 were used to model polyethylene glycol and glycidyl azide polyether, respectively. It is found that AlH3 is more sensitive to temperature changes than its oxide layer. Upon contact between the alumina layer and CH3OC2H5 or CH3N3, these compounds exist stably on the α-Al2O3(0001) and γ-Al2O3(110) surfaces. Upon direct contact with the α-AlH3(010) surface, CH3OC2H5 is relatively stable, while CH3N3 can trigger the surface hydrogen transfer reaction due to the low energy barrier(5.0 kcal/mol). The current work provides a theoretical basis for understanding the sensitivity of AlH3 and binders containing COC or –N3 groups, and is useful in the research and development of superior composite energetic propellants.

Enhancement strategy of mechanical property by constructing of energetic RDX@CNFs composites in propellants, and investigation on its combustion and sensitivity behavior

In the domain of energetic materials (EMs), the high-energy and high-strength propellants are always what are the scientists pursuing to satisfy the great demands of fast development and replacement for artillery. Recently, the emerging of cellulose nanofibers (CNFs) has attracted great interests since its extraordinary performances like biocompatibility, carbon-neutral nature, tailorable surface chemistry, and unprecedented mechanical properties. Inspired by the fascinating high strengthen of CNFs, this study prepared a kind of energetic hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)@CNFs composites firstly, and then applied them in conventional double-based gun propellant (GP) to study its energy, combustion and mechanical, and sensitivity performances. The results of the mechanical properties demonstrated that the impact strength of RDX@CNFs-GP with different content of CNFs was improved by 34.9-104.7%, 7.1-39.4%, 14.4-51.2% under the condition of low, room and high temperature, the compression strength was improved by 8.6-49.5%, 4.3-45.9%, 6.2-47.8%, while the tensile strength was improved by 0.6-21.2%, 7.0-19.5%, 9.0-26.0%, respectively. Moreover, the impact and electrostatic spark sensitivities have also been increased by 21.8% and 61.8% in terms of the maximum value and exert favorable desensitization effect compared with blank sample. Notably, the propellant added with CNFs could burn steadily without anomalous combustion behavior, and the energy level of the RDX@CNFs-2.0%-GP (1180.70 J/g) maintain relative close value to that of RDX@CNFs-0%-GP (1184.84 J/g) with regard to the gunpowder impetus. Lastly, the enhancement mechanism of the CNFs in GP was discussed and proposal. Hence, this present work could potentially provide fundamental theory and data support for the development of CNFs in high-strength and high energy propellants.

Numerical simulation of fragment impacting solid rocket motors

For the initiation characteristics of solid rocket motors (SRMs) filled with high-energy solid propellant under fragment impact, the related theoretical critical criterion for shock initiation was established based on the critical energy criterion and equivalent analysis method. Afterward, numerical simulation of fragment impacting SRM was carried out by using the ANSYS/LS-DYNA software and the nonlinear finite element method. Based on the calculated pressure and reactivity in the high-energy solid propellant grain, the shock critical initiation velocity of SRM and its variation with different forms of fragments and impact conditions were determined. It is found that the numerical simulation results under typical conditions are in good agreement with the data calculated with the developed theoretical critical criterion for shock initiation of SRM. However, the shock initiation mechanism becomes more complex when the case thickness of SRM increases to more than 5 mm; thus, the applicability of the developed theoretical critical criterion reduces. Moreover, it is found that all the case thickness, fragment shape, material properties of the fragment, and impact attitude can significantly affect the shock critical initiation velocity of SRM, even the initiation position and time. First, the critical velocity increases linearly with the increase in case thickness, and the increment rate is faster beyond the thickness of 6 mm. Second, the shock critical initiation velocity induced by fragments with different shapes is as follows: spherical fragment > cubic fragment > cylindrical fragment, while the initiation capacity of different fragment materials is ranked as follows: tungsten alloy > 45 steel > 2024 aluminum. Third, the effects of impact attitude on the shock critical initiation velocity, position and time are complex, and these effects are also influenced by fragment shape. When the impact angle is less than 60°, there is a higher shock critical initiation velocity of SRM under inclined impact than that under positive impact. In addition, the critical velocity induced by cubic fragment is the highest under the combination of vertex impact and positive impact. The variation of the critical velocity under this condition is approximately consistent with that by impacting with cylindrical fragment. Furthermore, when the impact angle is greater than 60°, the shock critical initiation velocity of SRM is less obviously influenced by impact attitude and fragment shape. Meanwhile, the critical velocity decreases sharply under this condition, which indicates that it is easier for SRM to detonate.