Hasil untuk "Explosives and pyrotechnics"

Mohammed Jouini, Amir Abdelaziz, Ahmed Fouzi Tarchoun et al.

This study presents a double modification strategy to enhance hydroxyl‑terminated polybutadiene (HTPB) properties as an energetic binder. HTPB was chemically nitrated to obtain nitro-HTPB (NHTPB), then blended with nitrocellulose (NC) at different ratios of 10%, 30%, and 50%. The morphological evaluation revealed a uniform NC dispersion within a smooth binder surface. Fourier-transform infrared spectroscopy confirmed successful nitration and homogeneous NC incorporation. As the NC content increases, the enhancement in density, thermal stability, and combustion behavior becomes more pronounced for which the best performance is observed at 50% NC—where NHTPB density increased by approximately 46.72% compared to the pure HTPB. Differential scanning calorimetry analysis revealed a 28 °C shift to higher temperatures for the glass transition, while the thermogravimetric Analysis indicated a lower onset decomposition temperature, accompanied by a 13% reduction in residual mass. Kinetic analysis, performed using an isoconversional method, showed a 19.52% and 30.05% decrease in activation energy for the first and second decomposition stages, respectively, compared to pure HTPB. This reduction is attributed to the catalytic effect of nitrate groups, although the effect diminished slightly with increasing NC content. The impact and friction sensitivity tests confirm that 30% of the NC doping level provides the optimal compromise between safety, handling, storage, and energetic performance for effective propellant applications.

Chuanyu PAN, Xilong HUANG, Ping LI et al.

To develop an engineering model based on the physical mechanism of the non-shock initiation reaction of structural charge, which can be used to describe the reaction evolution process and quantify the reaction intensity for evaluating weapons and ammunition safety. Considering the cavity expansion volume, a constrained charge combustion reaction evolution model was established in this paper, with fracture toughness and reaction pressure as the main parameters based on the main control mechanism of charge reaction crack propagation, which can describe the combustion gaseous product pressurization and shell constraint strength during combustion evolution. Relevant details for the control model establishment process were given. The model reliability of confined charge reaction combustion evolution was verified via the experiments of PBX-3 (87% HMX) explosive combustion reaction evolution under mass inertial confinement. The mass velocity time was recorded by PDV (photonic Doppler velocimetry) transducers, the pressure-time profiles were recorded via pressure transducers, and the experimental process was captured via a high-speed camera. The experimental results were compared with calculated results from the control model proposed in this work. The results show that the reaction pressurization process calculated via the model is roughly consistent with the pressure-increasing trend in the experiment (calculated by the mass velocity). The control model considering the structural venting effect can reflect the competition mechanism between combustion gas pressurization and venting in the pressure-increasing process, and the relationship between the pressure-increasing trend and the vent coefficient is in line with the mechanism analysis expectation. The results can support deepening the understanding of the accidental explosive combustion reaction evolution mechanism.

Chu GAO, Xiangzhen KONG, Yongsheng JIA et al.

To investigate the shear-enhanced compaction effect and strain-rate effect on the equation of state (EoS) of concrete-like materials subjected to blast and impact loadings, high-fidelity numerical simulations were performed based on two types of EoS behavior tests for cement mortar, including hydrostatic compression tests and flyer-plate impact tests. These simulations employed the Kong-Fang hydro-elasto-plastic model for concrete-like materials and were implemented using the smoothed particle Galerkin (SPG) algorithm in LS-DYNA, enabling accurate reproduction of complex dynamic mechanical behaviors, including the shear-enhanced compaction effect and strain-rate effect. Based on the high-fidelity numerical simulations described above, a quantitative analysis was conducted to investigate the influence of the shear-enhanced compaction effect and strain-rate effect on EoS behavior of concrete-like materials, and the challenges associated with eliminating the shear-enhanced compaction and strain-rate coupling effects in flyer-plate impact tests were systematically identified. The results demonstrate that the Kong-Fang model, when combined with the SPG algorithm, can accurately simulate the complex dynamic mechanical behaviors of concrete-like materials, including shear-enhanced compaction effect and strain-rate effect. To achieve high-precision simulation of dynamic mechanical behaviors of concrete-like materials subjected to blast and impact loadings across high-medium-low pressure ranges, it is essential to establish an EoS with a wide-range pressure based on experimental data from EoS behavior tests. However, shear-enhanced compaction and strain-rate coupling effects should be eliminated when using flyer-plate impact test data to calibrate the EoS parameters. A paradox arises in the establishment of EoS with wide-range pressure for concrete-like materials, and the application of numerical iteration correction methodology may represent an effective approach to resolving this challenge. These findings provide a theoretical foundation for the future development of a numerical iteration correction methodology to eliminate the shear-enhanced compaction effect and strain-rate effect on the EoS of concrete-like materials, thereby facilitating the establishment of a high-precision EoS with a wide range of pressure for concrete-like materials subjected to impact and blast loadings.

Dariya V. Maksimova, Igor.L. Dalinger, Irina A. Vatsadze et al.

WeiQiang Pang, Oleg G. Glotov, Volker Gettwert et al.

Svatopluk Zeman, Veerabhadragouda B. Patil

The literature widely reported information about apparent high impact sensitivities of both the pure 2,4,6-trinitrotoluene (TNT; i.e. of 14–16 J) and ɛ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ɛ-CL20; i.e. of 2–4.4 J), which mostly correspond to the BAM method of determination. This brief overview discusses the reasons of these error data. The physical organic chemistry approach to this problem has confirmed the Beijing Inst. of Technology value of 13.2 J for ɛ-CL20 and the LANL value of 39.2 J for TNT. The morphological instability of ɛ-CL20, when in contact with polar binders or plasticizers, might not have much influence on its application in propellants. The stabilization of ɛ- to β-CL20 upon its entry into a cocrystal with a coformer having the character of a polynitro compound (especially with nitramines) could be of practical importance. The high impact sensitivity of TNT and ɛ-CL20 is important for handling and processing safety when related to the specific practical samples. However, they cannot be used for molecular-structural analyses and predictions or as a comparative standard, which is currently widespread in the literature.

Luyao MA, Xianfeng ZHANG, Wei XIONG et al.

Porous materials exhibit pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, a theoretical analysis of the relationship between the shock wave formation process and the pore collapse behavior of porous materials is conducted. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock waves, it is proposed that the shock wave structure of porous materials has three modes: low-pressure single wave mode, double shock wave mode, and high-pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.

Hongyu ZHANG, Runqiang CHI, Miao SUN et al.

Impact ejecting is a critical part of the impact process and plays a pivotal role in engineering applications and scientific analyses in deep space exploration. Its importance extends to space missions such as asteroid surface anchoring for mission stability, impact sampling for scientific analysis of extraterrestrial materials, kinetic impact deflection for planetary defense strategies, and the detailed analysis of ejecta deposition patterns on planetary surfaces to understand surface evolution and regolith dynamics. With small asteroids whose surfaces are commonly covered with regolith, granular targets are employed in laboratory settings to simulate the impact ejecting process. This paper presents a review of the research progress concerning the behavior of impact ejecting on granular targets. The formation process of impact ejecting and methods for describing ejecta curtains are evaluated. An analysis of the dimensional similarity laws governing impact ejecta, along with their applicability and limitations, is conducted. Additionally, the influence of factors, such as target material parameters, impact conditions, target surface morphology, and impactor shape and structure, on impact ejecting behavior is summarized. Finally, existing research challenges are objectively identified, and potential directions for further scientific research about the behavior of impact ejecta on granular targets are proposed.

M.D. Umbharatwala, S.S. Raut, Manmohan Dass Goel

In order to evaluate the ballistic performance of ceramic/fabric composite panels developed using 99.5 % alumina, Kevlar® and carbon fiber fabrics; a series of experiments were performed on the physical samples. The composite-projectile interaction was investigated in detail by means of finite element analysis using LS-DYNA®. The validated numerical model of the ceramic/fabric composite system was tactically modified to investigate the composite/projectile interaction for simultaneous projectile impacts at different impact velocities. The numerical model predicted the failure mechanism of the composite panel and the exit velocity of the projectile piercing through the composite accurately. This study reveals the important aspects of ballistic impact on composites under simultaneous multiple projectile impact condition which in turn, is a much more complex and critical case as compared to sequential multiple projectile impacts.

Shixu GUO, Xiang HE, Fei LIU et al.

In recent years, polyurea-coated reinforced concrete (RC) slabs have been extensively studied both experimentally and numerically for structural strengthening against contact explosions. However, theoretical investigations remain limited, particularly concerning the impact of polyurea on the local damages of the RC substrates. In this paper, an analytical model based on stress wave propagation theory was proposed to investigate the reflection of compression waves at the backside of the RC substrate slab and predict the spalling depth. Utilizing this analytical model, a quantitative and detailed discussion was presented regarding the effect of the polyurea on the critical spalling and breach of the RC substrate slab. Furthermore, the applicability of the empirical breach prediction, originally developed for uncoated RC slabs, was validated through existing experiments to predict the breach of polyurea-coated RC substrate slabs. The results indicate that polyurea affects the spalling process of the RC substrate slabs. Specifically, the net stress wave adjacent to the concrete-polyurea interface is a compression wave, while it transitions to a tensile wave in the deeper concrete. Polyurea primarily impacts the first spall of the RC substrate slab; subsequent spalling processes after the first spall align with those observed in uncoated RC slabs. Upon the occurrence of critical spalling, polyurea enhances the critical spalling resistance of RC slabs, although it significantly increases the spalling depth. Conversely, when a breach occurs, polyurea reduces the number of spalls but minimally affects on the total spalling depth. Based on these findings, the empirical method for predicting breaches of uncoated RC slabs can effectively be applied to predict the breach of RC substrate slabs coated with polyurea. The test results from more than twenty contact explosion experiments are consistent with the predicted outcomes, thereby validating the effectiveness of the analytical model and providing a method for estimating the breach of polyurea-coated RC substrate slabs.

Jiarong Zhang, Huan Huo, Lianjie Zhai et al.

The skeleton structures of azine (including diazine, triazine and tetrazine) are widely used as important candidate for building good performance energetic materials due to their uniform electron distribution, planar aromaticity, multi reactive sites and low ring tension. Introducing N-oxide coordination bonds into azine framework turns out to be an important and highly rewarding protocol for the construction of energetic compounds with balanced performances. A variety of energetic compounds with good comprehensive performances have been designed and synthesized by introducing NO coordination bonds to azine skeletons. In this work, a review of recent research in the synthesis and physicochemical properties of N-oxides energetic compounds based on diazine, triazine and tetrazine skeleton is presented. And the application research progress of typical N-oxides energetic compounds are introduced.

Wenxiang Bian, Yaning Li, Peng Bao et al.

Ammonium dinitramide (ADN) is a high-performance, novel green oxidizer that is commonly used in solid propellants. It offers advantages such as a large oxygen balance and significant gas release, making it a promising candidate for use as an oxidizing component in composite explosives. To explore the application of ADN in composite explosives, this study investigates the compatibility between ADN, cyclotrimethylene trinitramine (RDX), aluminum powder, and thermoplastic polyurethane (TPU), addressing the safety concerns associated with the use of ADN in composite explosives where RDX serves as the primary explosive. Based on this research, a series of formulations were designed, and theoretical calculations related to detonation parameters were conducted, with ammonium perchlorate (AP) serving as a parallel control to examine the detonation performance of ADN-based composite explosives. Finally, granulated powder was prepared according to the formulations to assess the mechanical sensitivity of ADN-based composite explosives. The results indicate that ADN exhibits good compatibility with RDX, aluminum powder, and TPU. Theoretical values for detonation heat, detonation velocity, and detonation volume of ADN-based composite explosives are all greater than those of AP-based composite explosives, displaying certain patterns with variations in RDX content or the ratio of aluminum powder to oxidizer. Furthermore, maintaining a moderate ratio of aluminum powder to oxidizer while reducing the content of the primary explosive can effectively lower the mechanical sensitivity of ADN-based composite explosives.

Pavel S. Gribov, Natalia N. Il'icheva, Natalia N. Kondakova et al.

The creation of novel energetic polymers for future advanced solid composite propellants and gunpowder is an urgent area of modern research. A simple and effective waste-free cycloaddition reaction between dialkyne and diazide comonomers, both bearing nitramine groups, for the synthesis of an energetic polymer containing explosophoric units in the polymer chain has been described. Neither solvent nor catalyst is required for the production of this polymer, the comonomers used are readily available, and the product does not need any purification, and, importantly, this protocol scales well. The resulting polymer, C1Z1, (C14H22N12O8)n, was comprehensively characterized by spectral and physico-chemical methods. Compatibility with energetic plasticizers (NG, DNDEG, DANPE), thermochemical characteristics and combustion features indicate the prospects of target polymer C1Z1 (density, ρ = 1.484 g/cm3; onset temperatures is 230 °C; positive enthalpy of the formation, ΔHf0 = +636 kJ/kg; burning rate at 10 MPa is 9.5 mm/s) as a binder base for energetic materials. Comparison of C1Z1 with nitrocellulose (NC) and their compositions with plasticizers revealed the advantages of C1Z1.

Haotian Jian, Guoqiang Zheng, Lejian Chen et al.

Exploding foil initiator (EFI) is a kind of advanced device for initiating explosives, but its function is unstable when it comes to directly igniting pyrotechnics. To solve the problem, this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics. An oscilloscope, a photon Doppler velocimetry, and a plasma spectrum measurement system were employed to obtain information of electric characteristics, impact pressure, and plasma temperature. The results of the electric characteristics and the impact pressure were inconsistent with ignition results. The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration (HTD). It eventually concludes that the ignition mechanism in this research is the micro-convection heat transfer rather than the shock initiation, which differs from that of exploding foil initiators detonating explosives. Furthermore, the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper. The HTD is the critical parameter for judging the ignition success, and it is influenced by two factors: the late time discharge and the energy of the electric explosion. The longer time of the late time discharge and the more energy of the electric explosion, the easier it is to expand the HTD, which improves the probability of the ignition success.

Luigi T. DeLuca, Adriano Annovazzi

Burning rate plays a crucial role in determining the performance of solid rocket motors (SRMs). In the traditional approach for solid propellant propulsion, technical activities regarding burning rates are developed at three different operational levels: (i) Strand burners or laboratory-scale devices in general; (ii) Small-scale motors (SSMs); And (iii) full-size or end-item rocket motors. While strand burners are extensively used for propellant development (formulation exploration, ingredients screening, performance verification, and production control) and relatively little is done experimentally at the full-size motor level (being large-scale experimentation too expensive and dangerous), a lot is usually carried out at SSM level to obtain burning rate information under motor operating conditions. In the introductory part of this work, burning rate fundamentals are recalled and burning rate measurement devices are quickly summarized. Then, a survey of subscale motors is conducted and several automated procedures to deduce burning rate from SSM testing are analyzed. Data reduction methods commonly used by leading European companies are based on the thickness-over-time (TOT) definition. Attention is dedicated to procedures used in Italy and France for quality control of the European space launchers (solid propellant boosters of Ariane family and core solid rocket motors of VEGA family). In addition, automated data reduction methods based on mass balance (MB) and often used in USA are investigated. Specific features and general trends of the tested industrial procedures are pointed out. Since for any tests the actual burning rates are unknown, results can only be compared based on the statistical quality of the deduced ballistic data. Mainly reproducibility, ease of application, and suitability for automated computer implementation are of interest to industrial users. The effects of test variability, input data quality, and data reduction methods on result reproducibility are discussed with reference to fire tests of the successful Ariane-5 solid boosters. The systematic analysis of industrial data conducted in this work suggests that improving the actual mix reproducibility and quality of experimental data is more important than perfecting the current data reduction methods. Moreover, the international trends suggest that the fundamental TOT procedures are being replaced by MB procedures or advanced TOT procedures with burning times evaluated using pressure integrals.

Lukas Bauer, Maximilian Benz, Thomas M. Klapötke et al.

In the field of energetic materials, traditional materials with high toxicity or other disadvantages are mostly used. There is an urgent need for trinitrotoluene replacements (TNT), which itself is toxic and its production is problematic due to red wastewater. New materials should be safe to handle, have good performance, and be inexpensive to synthesize. Nitratoalkylazoles are known to have low melting points and good energetic properties compared to TNT. In this paper, seven energetic compounds are synthesized starting from 5-methyltetrazole, 5-hydroxymethyltetrazole and 4,5-bishydroxymethyltriazole. The nitrates are characterized in terms of their physical, chemical, and energetic properties. Of those seven compounds, five are solid, melting between 27 °C and 110 °C, and two are liquid. Methylation and hydroxyalkylation were performed and discussed extensively. The organic nitrate is introduced in the last step so that the synthesis remains safe and scalable. Correlations between the molecular geometry and the melting points are explained. Calculations indicate detonation velocities that are 6%–11% higher than those of TNT. A discussion of the effect of isomerism on the properties leads to surprising insights and should help focus and accelerate research on the replacement of TNT.

Carole Rossi, Ruiqi Shen

Pyrotechnic systems, also termed pyrotechnics, refer to a broad family of sophisticated single-use devices that are able to produce heat, light, smoke, sound, motion, and/or a combination of these thanks to the reaction of an energetic material (primary and secondary explosives, powders/propellants, and other pyrotechnic substances) [...]

Han Shi, Jiaqi Ren, Weiqiang Tang et al.

In order to solve the problem of weak injection of fuel-rich propellant and to enhance its burning rate, the combustion behaviors of Al/Mg-based fuel-rich HTPB propellants with 40wt% metal content were studied with and without the addition of fast burning compound hydrated tetra-(4-amino-1, 2, 4-triazole) copper perchlorate (ACP) and burning rate catalyst Pb5. The results show that the burning rates of the Al/Mg-based fuel-rich HTPB propellants with the addition of fast burning compound and catalyst increase significantly, and the pressure exponents decrease. With the increase of pressure, the fluctuation of burning interface of the propellants increases and the flame height decreases. Compared with the Mg-based propellants of high burning rate, the agglomeration of condensed combustion products of the Al-based propellants is much more serious; the combustion extent of aluminum in the Al-based propellants is obviously lower than that of magnesium in the Mg-based propellants. These results are very meaningful for the design of fuel-rich HTPB propellants with high performance.

Bae-Seong Kim, Juho Lee

Pyrotechnic-separation devices are widely used in the separation mission of satellites and projectiles. The pyroshock generated by the pyrotechnic-separation device can cause serious damage to surrounding electronic equipment owing to its high-frequency characteristics, which leads to mission failure. Therefore, solving the pyroshock problem is necessary. Typically, attenuation of the pyroshock propagation based on the understanding of the shock-propagation characteristics of a structure is possible. However, as pyrotechnics (or explosives) cannot be used for every pyroshock-propagation experiment due to the high cost and risk, a device for simulating a pyroshock environment that does not use pyrotechnics is required. In this study, a pyroshock simulator was developed, which could generate the desired shock environment by controlling shock environment-generation variables and be tested for any test structure. For this purpose, a resonator attached to the test structure and a pneumatic launch device was designed and fabricated. A resonator that generates a desired shock environment was designed by predicting the shock generation through impact analysis. A pyroshock simulator that generates a shock like an actual pyroshock was developed through comparison with the shock-response spectrum of a pyrotechnic initiator. The repeatability was verified, and the frequency and magnitude of the shock generated by the pyroshock simulator could be controlled by adjusting the collision velocity of the steel ball and the thickness of the resonator disk.

Jun Tao, Xiaofeng Wang, Jinhua Wang et al.

In order to study reactivity and reaction mechanism of Al-polytetrafluoroethylene (PTFE) mechanically activated energetic composites, reaction molecular dynamics simulation was carried out to predict the pyrolysis process of PTFE. Then the reaction mechanism of PTFE pyrolysis products with Al was calculated by using density functional theory (DFT). Furthermore, the concentrated ignition characteristics were characterized. Finally, the pressure and temperature during the reaction process of Al-PTFE were tested, and the chemical structure before and after heating reaction were researched. Calculation and experimental results show that the main pyrolysis products of PTFE are C2, F, CF2, CF and CF3, and the degree of polymerization has little effect on the pyrolysis products. Among CF2, CF and CF3, it can be found that the energy barrier of reaction between CF3 and Al is the smallest (only 2.39 kJ•mol−1). The mechanical activation process can give higher reactivity to Al-PTFE mixture during concentrated ignition process.The reaction process of the decomposition of PTFE starts at 718K, and then the thermit reaction between the free radicals of decomposition products and Al begins at 898K.