Hasil untuk "Explosives and pyrotechnics"

Qingsong DU, Yunlong LIU

Underwater explosions in deep-sea environments involve complex interactions, making both theoretical modeling and experimental validation particularly challenging. While previous research has provided valuable insights into the basic features of shock wave propagation and bubble dynamics in underwater explosions, most existing studies are limited to shallow water scenarios or narrowly defined environmental parameters. Systematic research on the laws governing shock wave loads from deep-sea explosions and their associated bubble pulsation under varying operational conditions holds critical academic significance. Numerical simulations were conducted utilizing a zoned solution algorithm for shock waves derived from the unified equation for bubble dynamics theoretical model. The algorithm enabled numerical simulation of shock wave peak pressure and pressure attenuation processes under diverse initial conditions. Comparative analysis with experimental data confirmed model reliability, demonstrating a mere 0.5% deviation between simulated and measured peak pressures and excellent agreement in pressure attenuation processes. The simulations specifically investigated the influence of water depth, stand-off distance, and explosive charge mass on the peak pressure of the underwater explosion shock wave and explored the variation patterns of the shock wave under different initial conditions through an in-depth analysis of the shock wave impulse and specific shock wave energy. Furthermore, employing the same theoretical model, the bubble pulsation characteristics within a single cycle under varying water depths and explosive charge masses were comparatively analyzed. Traditional empirical formulas were employed to analyze the numerical simulation results, and dimensionless treatment was conducted on the parameters. The results reveal that the peak pressure of the shock wave is primarily influenced by the charge mass and stand-off distance, and increases with water depth at an approximate rate of 1% per kilometer. In contrast, both shock wave impulse and specific shock wave energy decrease with increasing water depth and stand-off distance, but show a positive correlation with charge magnitude. The bubble pulse radius is primarily determined by both the charge weight and the water depth, with the bubble pulsation phenomenon becoming attenuated in deep-water environments. Compared to the traditional Cole empirical formula, the simulated bubble pulse radius is reduced in the range of 0.1 to 10 km. The simulation indicates an asymmetry in the pulsation cycle: the expansion phase consistently lasts slightly longer than the collapse phase. These findings contribute to a more nuanced understanding of underwater explosion phenomena in deep-sea environments and have practical implications for naval engineering, subsea structural safety assessment, and explosive ordnance disposal in complex oceanic settings.

Jianfeng XUE, Xufeng ZHAO, Aiguo PI et al.

To enhance the damage efficiency of fluoropolymer-based reactive fragments and broaden their application range, a novel core-shell composite structure active fragment has been proposed. To improve the strength of the matrix material, carbon fiber was introduced via a wet mixing method. Under specific sintering conditions, two types of samples were prepared: PTFE/Al/CF tungsten powder and PTFE/Al/CF tungsten ball. The basic mechanical properties of these samples were tested. The addition of tungsten powder was found to increase the dynamic compressive strength of the composite. Penetration tests were conducted on 3 mm+3 mm+2 mm+2 mm multi-layer interval aluminum targets using both types of fragments. The experimental data were automatically processed using a Python-based program, yielding the perforation area, deformation volume, and reaction light intensity for each layer of the target plate. The damage characteristics of the multi-interval target under different velocity and constraint conditions were compared and analyzed. The results show that the core-shell type fragment exhibits superior penetration ability. It can penetrate all four layers of the target plates at low speeds, although the perforation area is relatively small, with a perforation diameter approximately 0.95 times the fragment diameter. In contrast, the homogeneous fragment has a larger perforation area but weaker penetration ability. Its perforation diameter is about 1.21 times the fragment diameter, and it can only penetrate three layers of target plates at high speeds. The steel shell constraint significantly enhances the punching and penetration capabilities of the fragments. The primary active reaction of the fragment occurs during impact with the second layer of the target. The energy release reaction has a limited effect on improving the punching effect. The differences in damage characteristics are mainly attributed to the mechanical properties of the fragments. These findings provide valuable insights for the structural design and damage effect evaluation of reactive fragments.

Zhicheng CAI, Zejian XU, Changzeng FAN et al.

To address the longstanding challenge of accurately evaluating the dynamic fracture toughness of ceramic materials, a new mode I dynamic fracture testing method was developed based on the conventional split-Hopkinson pressure bar (SHPB) technique. This approach introduced a miniature fracture specimen specifically designed to ensure pure mode I loading, along with a custom fixture system that enabled stable and repeatable dynamic fracture experiments on alumina ceramics with varying loading rates. The combined experimental-numerical method was used to obtain the variation of the mode I dynamic stress intensity factor at the crack tip under different loading rates. Fracture initiation time was obtained with high precision using the strain gauge method, allowing for the determination of mode I dynamic fracture toughness. To further validate the accuracy of the measured fracture initiation time, high-speed photography was employed to capture the entire failure process in real time and corroborate the onset of fracture of the tested specimens. The results show that as the applied loading rate increases from 0.45 TPa·m1/2·s−1 to 1.83 TPa·m1/2·s−1, the dynamic fracture toughness of alumina ceramics rises significantly from 8.39 MPa·m1/2 to 15.76 MPa·m1/2, indicating a pronounced strengthening effect induced by higher loading rates. Meanwhile, the crack initiation time decreases notably with increasing loading rate. Fractographic analysis using scanning electron microscopy reveals a clear fracture mode transition behavior. Under lower loading rates, the fracture of alumina ceramics predominantly exhibits intergranular fracture features. Under higher loading rates, the fracture shows a mixed-mode fracture involving both intergranular and transgranular features. This transition is attributed to the activation and propagation of more micro-defects under higher rates, resulting in increased microcracking. The emergence of this mixed fracture mode is associated with greater energy dissipation, which fundamentally contributes to the increase in mode I dynamic fracture toughness. The proposed method offers a robust framework for accurately assessing the mode I dynamic fracture properties of ceramic materials.

Min LI, Huahua XIAO

Study on gas deflagration-to-detonation transition (DDT) is of great significance for the research and development of industrial explosion prevention and detonation propulsion technology. Staggered array of obstacles is a typical obstacle layout that may be involved in the gas ignition and explosion scenario. Its existence usually significantly promotes the occurrence of DDT. In view of the lack of understanding of DDT in staggered array of obstacles, high-precision algorithm and dynamic adaptive grid were applied to solve the two-dimensional, fully compressible reactivity Navier-Stokes equations coupled with a calibrated chemical-diffusive model. Numerical investigation on the initiation process of DDT of premixed hydrogen and air in staggered array of square obstacles under different obstacle spacings was carried out. The results showed that decreasing obstacle spacing is beneficial to increase flame surface area in the early stage of flame acceleration and enhance compression of unburned gas by shock wave in the later stage, thus shortening DDT run-up time and distance. However, when the obstacle spacing is reduced to a threshold value, stuttering detonation occurs and the DDT run-up distance increases. The occurrence of DDT is mainly caused by the interaction between the flame and the shock wave reflected from the front wall of obstacle. The detonation partially decouples when it diffracts around an obstacle. Detonation re-initiation may be triggered when the decoupled detonation collides with a wall or with the shock wave or failure detonation wave from the other side of the obstacle. If the obstacle spacing is too small, the shock wave intensity decays significantly during detonation decoupling. This can easily lead to detonation failure. In addition, shock waves can be reflected off the staggered array of square obstacles in the vertical and parallel directions to the flame propagation direction, which help shock waves to act on the flame and unburned gas mixture. Therefore, DDT is more likely to be initiated in the staggered array of square obstacles than that of circular obstacles.

Shanyu XIAO, Xiaowang SUN, Weiwei QIN et al.

In order to address the needs of modern combat vehicles for both personnel protection and lightweight design, optimizing their blast-resistant structures is necessary. Due to the high cost of physical experiments, finite element simulation has been commonly used instead. However, simulations of explosion and vehicle responses require extensive computational resources and incur high computational costs, leading to limited data availability for the optimization of explosion-proof structures. Since structural optimization demands sufficient data support, larger amount of valid data can improve the accuracy of the surrogate model and the precision of the optimal solution, yielding better optimization results. To overcome these challenges, a data-driven optimization method for vehicle’s explosion-proof structures was proposed, integrating data augmentation and semi-supervised regression. To address the limitations of generative adversarial networks (GANs) in handling numerical data, an improved model, a Gaussian density estimation-Wasserstein generative adversarial network (GDE-WGAN), was developed by modifying both the generator and discriminator of the WGAN model, a variant of the GANs. The feasibility of the proposed method was demonstrated based on the principle of information gain. The data generated by the GDE-WGAN were incorporated into a self-training framework, where an adaptive confidence assessment mechanism dynamically adjusted the way that the semi-supervised support vector regression model utilizes the generated data. The feasibility and superiority of the method were validated by comparing the enhanced performance of the semi-supervised regression model using different numerical data expansion techniques. Finally, multi-objective optimization was performed to obtain the optimal solutions of the data-augmented semi-supervised regression model and the initial model, followed by verification and comparison with finite element simulation results. It shows that the GDE-WGAN significantly enhances the performance of the semi-supervised regression model, and the generated data exhibit greater randomness and diversity through the network structure of the GANs, which benefits semi-supervised learning. When handling semi-supervised regression for high-dimensional nonlinear numerical data, both global and local data distribution similarities play a crucial role. Furthermore, finite element simulations indicate that the improved model predicts results more accurately than the initial model and achieves superior optimization outcomes.

Qiushi HU, Yang HE, Suyang ZHONG et al.

Modeling powder is used to simulate the highly fragmented state of pressed explosives resulting from collisions, and the gap extrusion ignition behavior of PBX modeling powder is studied. Experiments were designed based on the way of projectile impact method. To ensure that no flow space exists except the designed gap, the surface of the sample was covered with cushion and coated with grease for sealing. The movement and reaction of molding powder squeezing into the gap were recorded by high-speed photography. By changing the ratio of gap area to sample cross-sectional area, the influence of compaction on ignition was studied. The results show that in the absence of grease seal, PBX molding powder undergoes particle crushing and compaction, and then the compacted molding powder is extruded from the clearance near the cushion, and ignition occurs in the extrusion process. The ignition position is at the interface between explosive and cushion. In the case of grease seal, PBX molding powder does not ignite for a period of time after compaction. When the indenter moves halfway, a wedge-shaped slip zone is formed, and a slip-dead zone interface could be seen in high-speed camera photos. Then the deformation mode evolves from single-wedge slip zone to double-wedge slip zone, and the shear effect of slip-dead zone interface does not cause ignition. At the later stage of loading, the indenter travels close to the gap surface, and the wedge-shaped slip zone disappears. Before and after the collision between the indenter and the gap, the explosive ignites once in each instance. Compaction effect has an important influence on ignition behavior. After compaction, the threshold value of ignition speed is obviously reduced, with the impact speed required to cause ignition being merely 4.5 m/s.

Nassima Sahnoun, Amir Abdelaziz, Memdouh Chebbah et al.

Double-base energetic composites have garnered substantial attention, particularly in aerospace, rocket, and missile applications. This class of materials offers diverse burning rates, high specific impulses, exceptional operational performance, and robust mechanical properties. In this study, we present a novel energetic composite produced by integrating ammonium perchlorate (AP) into a double-base energetic matrix composed of potato nitrostarch (NPS) and diethylene glycol dinitrate (DEGDN). The optimal composition of AP@NPS-DEGDN was determined through theoretical performance calculations using CEA-NASA program. The structural and morphological properties of the obtained composite were analyzed using FTIR and SEM techniques. The results indicated that the addition of AP did not modify the chemical structure of the baseline composite NPS-DEGDN. The thermal analysis by TGA revealed that the incorporation of 50 wt.% of AP enhanced the decomposition of the NPS-DEGDN matrix, while the NPS-DEGDN matrix simultaneously promoted the decomposition of AP. The DSC results indicated that the decomposition peak temperatures of the AP@NPS-DEGDN composite shifted to lower values, compared to the NPS-DEGDN matrix, highlighting the synergistic catalytic effect between the ingredients with an increase in heat release during the decomposition. Finally, the impact of various compounds on the thermal decomposition kinetics of AP@NPS-DEGDN was investigated using advanced model-free kinetic approaches, which revealed a significant reduction in the activation energy barrier, confirming the pronounced catalytic effect across the different decomposition stages of AP@NPS-DEGDN. These findings underscore the potential of the developed AP@NPS-DEGDN composite as a promising candidate for advanced energetic applications.

Vladica S Bozic

Composite propellants are widely used in applications ranging from gas generators and small rockets to large rocket systems in space programs. This study presents a novel thermoplastic elastomer (TPE) binder system based on oxygen-enriched polyether-block-amide (PEBA) copolymer, designed to enhance the performance of composite propellants while reducing waste and environmental impact. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to characterize the TPE binder, revealing favorable thermal and structural properties. The burning rate of propellants incorporating this binder was evaluated using ammonium perchlorate (AP) oxidizer of varying particle sizes and aluminum (Al), with and without the addition of lithium fluoride as a burning-rate modifier. Results demonstrate that the oxidizer particle size significantly affects the burning rate, and lithium fluoride effectively reduces it, depending on its concentration in the propellant formulation. Compared to traditional hydroxyl‑terminated polybutadiene (HTPB)-based systems, propellants formulated with the PEBA-based binder exhibit improved energy performance, comparable burning rates, and advantageous processing and aging characteristics, all at a reduced cost.

Sri Nithya Mahottamananda, Yash Pal, Narendra Yadav et al.

The performance of hybrid rocket propulsion systems can be significantly enhanced by incorporating metal additives in solid fuels. This study investigates the ignition, combustion, and regression rate of hydroxyl‑terminated polybutadiene (HTPB)-based solid fuels supplemented with Boron (B) and Viton. The investigated fuel compositions comprise pure HTPB, HTPB with 10 wt.% and 15 wt.% B (designated H-B10 and H-B15), and HTPB containing B@Viton composites with 10 wt.% and 15 wt.% B@Viton (denoted as H-B10V10 and H-B15V10). Ignition and combustion experiments were conducted using a counterflow burner to assess the influence of B@Viton additives on HTPB-based solid fuels under varying oxygen mass flux conditions. To understand the thermal decomposition and oxidation behavior of B@Viton additives, thermogravimetric-differential scanning calorimetry (TG-DSC) was conducted, followed by an analysis of their oxidation behavior within the HTPB matrix. Results revealed that the addition of Viton altered the oxidation kinetics of B, leading to faster decomposition and gasification. Incorporating 10 wt.% B@Viton in HTPB (H-B10V10) resulted in a 52% regression rate increase compared to pure HTPB at an oxidizer mass flux of 74 kg/(m2·s). Pure HTPB had the shortest ignition delay time with 227 ms, the ignition delay time increases with an increase in the weight percentage of B, except for Viton-coated samples H-B10V10 (232 ms) and H-B15V10 (241 ms). A proposed combustion mechanism suggested that Viton enhances B combustion by facilitating oxide layer removal and promoting gas-phase reactions.

Cheng ZHENG, Yefei ZHU, Feng XU et al.

Experimental investigation of internal explosion effects on ship structures still faces fundamental challenges. The prohibitively high costs of specialized naval steel plates impose disproportionate financial burdens on experimental budgets. Additionally, the restricted availability of standardized thickness variants has dimensional scaling conflicts during reduced-scale internal explosion experiments. This research proposes an equivalent substitution method for scaled model testing. The methodology enables a strategic replacement of naval steel with conventional steel while maintaining response similitude during the internal explosion of ship structures. The primary research objective focuses on validating the equivalent substitution method for conventional steel as a replacement for specialized naval steel without degrading the accuracy of the recorded data. According to the principle of central deformation similarity, the equivalence relationship among target plates of different grades was established under the assumption of structural integrity during the explosion. Based on the theory of large deflection of thin plates, the relationship between plate thickness and deformation was clarified thoroughly. An equivalence substitution method for different plate grades was explained, and an equivalence substitution method for different plates was proposed. It provides a theoretical foundation for substituting specialized naval steel with conventional steel. Comprehensive numerical simulations were conducted using the finite element analysis software AUTODYN to validate the proposed method. The simulations modeled the dynamic response of four different grades of steel target plates (921A steel, 907A steel, Q235 steel, and Q355 steel) under internal blast loading. The maximum deviation between the simulation results and experimental data is only 5.6%, thereby fully confirming the accuracy and reliability of the numerical model. The equivalence relationships among grades under internal blast loading with different charge volume ratios (0.1, 0.2, 0.4, 0.8, and 1.0) were further explored through extensive numerical simulations involving four plates grades (Q235, Q355, 907A, and 921A) with various thicknesses. A fitting analysis of equivalent plate thickness was conducted. By integrating empirical formulas correlating equivalent plate thickness with dynamic yield strength, the substituted target plate showed less than 10% deviation in central deformation compared to the original plate. The proposed equivalence method for steel target plates of different grades under internal explosion loads has been demonstrated to be both rational and practically applicable. This provides a theoretical foundation and empirical reference for substituting specialized naval steel with ordinary steel in internal explosion experiments.

Santhosh G, J. Anju, Supriya N et al.

Propellant formulations containing a novel high nitrogen azotetrazole salt viz., diammonium 5,5′-azotetrazolate (DAAzT) along with two different binders viz., hydroxyl terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP) were realized as potential pyrogen-based gas generators for use in inflatable structures. The DAAzT-GAP and DAAzT-HTPB propellant systems were investigated for their gas generating capabilities and it was found that the GAP based system offers enhanced gas yield of ∼430 mL/g against ∼320 mL/g for the HTPB based propellant at standard operating pressure of 1 bar and temperature of 298 K. Combustion product analyses of the propellant were undertaken by pyro GC–MS and it was found that the combustion products are benign and constitutes 62% and 53% N2 (mass fraction) as major combustion products from GAP and HTPB propellant respectively. A detailed thermal analysis of DAAzT by isoconversional method of Vzayovkin was undertaken and the dependence of activation energy with conversion was evaluated. The activation energy was also determined using a classical Kissinger method. The impact and friction sensitivity of the promising GAP-DAAzT propellant was found to be 3 Nm and 360 N respectively and the auto ignition temperature is 177.0 °C. Functional evaluation and gas generating capability of DAAzT-GAP propellant were successfully demonstrated in a sub-scale inflation test in a stand-alone configuration.

Nawel Matmat, Amir Abdelaziz, Djalal Trache et al.

The current study presents a successful elaboration and characterization of an innovative energetic composite based on nitrocellulose and nitrostarch (NCNPS) dual-biopolymers, and ammonium perchlorate (AP). A pre-establishment of the optimal formulation of the AP@NCNPS composite has been determined through a theoretical estimation of the ballistic performance via CEA-NASA software. The obtained composites were then fully characterized by FTIR, DSC, and TGA analyses. The IR-spectroscopy depicted the presence of all the characteristic groups of ester nitrates, revealing that the incorporation of AP did not alter the chemical structure of the dual-biopolymers. The thermal analysis demonstrated a mutual catalytic effect between AP and NCNPS biopolymeric matrix supported by the decrease of the maximum degradation temperatures observed for all the decomposition stages of AP@NCNPS composite after the incorporation of the oxidizer. The thermo-kinetic investigation, carried out using linear and non-linear isoconversional approaches (TAS, VYA/CE) demonstrated a considerable reduction in the activation energy values, highlighting, once again the role of AP in the improvement of the thermolysis process of the prepared AP@NCNPS energetic composite.

Alexander G. Korotkikh, Daniil V. Teplov, Ivan V. Sorokin

Combustion of dispersed metals in an oxidizing environment is of practical interest, which is related to the prediction of characteristics of high-energy compositions (HECs) containing metal powders, as well as the characteristics of various propulsion systems and gas generators. The research studies peculiarities of ignition and combustion of dispersed systems of Al, B and Al-B mixture in gas products formed during thermal decomposition and combustion of HEC components. In the study of the characteristics of ignition and combustion, the development of flame processes, a continuous CO2 laser (high-speed radiant heating) and a continuous-pressure flow bomb (stationary combustion), including the filter system for the capture of condensed combustion products (CCPs) were applied. It was found that the high reactivity of dispersed Al reduces the ignition time and increases the burning rate of HECs, and increases the volume fraction of fine condensed particles. The use of amorphous B or Al-B mixture (17.2/82.8 mass ratio) increases the ignition time (up to 62%) and significantly reduces the burning rate of HECs, at the same time, the volume share of large CCPs increases due to the melting of the oxide layer on the surface of B particles and their increased cohesion. Analysis of CCPs showed that fine and large agglomerate particles were formed on the surface of the reactive HEC layer, which contain oxides of the metals used. When Al particles are burned together with B particles, complex oxides (aluminum borates) can be formed.

Sergey V. Bondarchuk

In this paper, we present a theoretical study of structure and UV-vis spectra of 11 colored complexes of nucleophiles with nitroaromatic energetic materials. Two different schemes were found to be the most suitable for absorption spectra simulation. In the case of covalently bound Meisenheimer complexes, the time-dependent density functional theory (TD-DFT) approach with the TPSS functional was the most accurate. Meanwhile, for intermolecular charge-transfer complexes, the closest spectral pattern was provided by the time-dependent Hartree-Fock (TD-HF) scheme with modified exchange contribution (40%). It has been found that the binding type is determined predominantly by the steric factors and less by the electronic effects of the nucleophile, which was approved by the quantum theory of atoms in molecules (QTAIM) analysis of the formed bond types and nucleophilicity index calculations. For the charge-transfer complex, an appropriate configuration with the intermolecular separation between the local electrophilic and nucleophilic sites (the C1···N distance) of about 3.1 Å, was revealed using both classical molecular dynamics simulations and geometry optimizations in polar continuum. Absorption energies and intensities of the electronic transitions are generally well-reproduced in all 11 cases and demonstrate a local π–π* excitation in the covalently-bound complexes and pure charge transfer in intermolecular system. The applied computational methods allow reproducing of the sample colors with a high degree of similarity, which may find their application for modeling of new reagents with other expected colorimetric characteristics.

A. V. Yudin, N. V. Dunina-Barkovskaya, S. I. Blinnikov

We present our calculations of the thermal neutrino radiation that accompanies the explosion of a minimum-mass neutron star. In this case, the neutrino luminosity is lower than the luminosity during a supernova explosion approximately by five orders of magnitude, while the energy carried away by neutrinos is low compared to the explosion energy. We also show that the energy losses through neutrinos do not hinder the envelope heating and the cumulation of the shock during its breakout and the acceleration of the outer part of the envelope to ultrarelativistic speeds.

Peng Peng, Tianlong Fan, Xiao-Long Ren et al.

Edges, binding together nodes within networks, have the potential to induce dramatic transitions when specific collective failure behaviors emerge. These changes, initially unfolding covertly and then erupting abruptly, pose substantial, unforeseeable threats to networked systems, and are termed explosive vulnerability. Thus, identifying influential edges capable of triggering such drastic transitions, while minimizing cost, is of utmost significance. Here, we address this challenge by introducing edge collective influence (ECI), which builds upon the optimal percolation theory applied to line graphs. ECI embodies features of both optimal and explosive percolation, involving minimized removal costs and explosive dismantling tactic. Furthermore, we introduce two improved versions of ECI, namely IECI and IECIR, tailored for objectives of hidden and fast dismantling, respectively, with their superior performance validated in both synthetic and empirical networks. Finally, we present a dual competitive percolation (DCP) model, whose reverse process replicates the explosive dismantling process and the trajectory of the cost function of ECI, elucidating the microscopic mechanisms enabling ECI's optimization. ECI and the DCP model demonstrate the profound connection between optimal and explosive percolation. This work significantly deepens our comprehension of percolation and provides valuable insights into the explosive vulnerabilities arising from edge collective behaviors.

Zhengfeng Yan, Tingting Lu, Yajing Liu et al.

For the development of safe, non-toxic and environmentally friendly gas generators, a nitrogen-rich compound 5,7-diamine-2-nitro-1,2,4-triazolo[1,5-a]-1,3,5-triazine (ANTT) was synthesized from 3,5-diamine-1,2,4-triazole in two steps. The structure of ANTT was comprehensively characterized and well investigated by X-ray diffraction. The thermal stability, detonation properties and mechanical sensitivities of ANTT were finely studied. ANTT, enjoyed with a high content of nitrogen (57.13%), as well as a high decomposition temperature of 358.5 °C, high self-accelerating decomposition temperature of 340.3 °C, high critical temperature of thermal explosion 342.2 °C, high apparent activation energy of 512.23 kJ•mol−1 and low sensitivity toward destructive mechanical stimuli (IS > 60 J; FS > 360 N), is promising candidate as gas generator.

Jiangfeng Pei, Zongkai Wu, Yiwen Hu et al.

In order to investigate the effects of plasticizers on the binding energy, solubility parameter and mechanical properties of pBAMO-b-GAP copolymer (the copolymer of 3,3′-bis(azidomethy) oxetane and glycidyl azide polymer), the related copolymer/plasticizer mixed systems were established by molecular dynamics simulations. Besides, the mechanical properties of the formulas based on pBAMO-b-GAP containing the three energetic plasticizers were also studied experimentally. The results showed that all involved energetic plasticizers could be miscible with the pBAMO-b-GAP. The order of binding energy was theoretically found to be pBAMO-b-GAP / BuNENA > pBAMO-b-GAP/ TMETN > pBAMO-b-GAP/ DIANP which was consistent with the trends of the experimental tensile strength values of three mixed materials. Excitedly, the DIANP showed strongest effects among the three plasticizers on improving the toughness of the copolymer according to the calculation of Cauchy pressure and experimental value of elongation. For the pBAMO-b-GAP copolymer, the DIANP could be a promising plasticizer and compolymer/plasticizer mixed system was suitable used as binder in azido polyether-based propellants.

Chun-Ming Yip, Ming-Chung Chu, Shing-Chi Leung et al.

We show that a minimum-mass neutron star undergoes delayed explosion after mass removal from its surface. We couple the Newtonian hydrodynamics to a nuclear reaction network of $\sim4500$ isotopes to study the nucleosynthesis and neutrino emission during the explosion. An electron antineutrino burst with a peak luminosity of $\sim3\times10^{50}$ erg s$^{-1}$ is emitted while the ejecta is heated to $\sim10^{9}$ K. A robust $r$-process nucleosynthesis is realized in the ejecta. Lanthanides and heavy elements near the second and third $r$-process peaks are synthesized as end products of nucleosynthesis, suggesting that subminimal neutron star explosions could be an important source of solar chemical elements.

Liliya Imasheva, H. -Thomas Janka, Achim Weiss

Thermal bombs are a widely used method to artificially trigger explosions of core-collapse supernovae (CCSNe) to determine their nucleosynthesis or ejecta and remnant properties. Recently, their use in spherically symmetric (1D) hydrodynamic simulations led to the result that {56,57}Ni and 44Ti are massively underproduced compared to observational estimates for Supernova 1987A, if the explosions are slow, i.e., if the explosion mechanism of CCSNe releases the explosion energy on long timescales. It was concluded that rapid explosions are required to match observed abundances, i.e., the explosion mechanism must provide the CCSN energy nearly instantaneously on timescales of some ten to order 100 ms. This result, if valid, would disfavor the neutrino-heating mechanism, which releases the CCSN energy on timescales of seconds. Here, we demonstrate by 1D hydrodynamic simulations and nucleosynthetic post-processing that these conclusions are a consequence of disregarding the initial collapse of the stellar core in the thermal-bomb modelling before the bomb releases the explosion energy. We demonstrate that the anti-correlation of 56Ni yield and energy-injection timescale vanishes when the initial collapse is included and that it can even be reversed, i.e., more 56Ni is made by slower explosions, when the collapse proceeds to small radii similar to those where neutrino heating takes place in CCSNe. We also show that the 56Ni production in thermal-bomb explosions is sensitive to the chosen mass cut and that a fixed mass layer or fixed volume for the energy deposition cause only secondary differences. Moreover, we propose a most appropriate setup for thermal bombs.