Ahmed Elbeih

A modified low-sensitivity explosive composition (LSX) based on DNAN/NTO/RDX had been previously synthesized and characterized, and its thermal decomposition kinetics were preliminarily investigated using Friedman and Ozawa–Flynn–Wall isoconversional methods. In the present work, the kinetic evaluation was extended using the Kissinger–Akahira–Sunose (KAS) and Vyazovkin isoconversional approaches. The slow cook-off response of LSX explosive was numerically simulated using COMSOL Multiphysics. Furthermore, the conversion-dependent kinetic parameters derived from the Vyazovkin model were further implemented in AKTS Thermokinetics software to assess the shelf life of the formulation. Differential scanning calorimetry and thermogravimetric analysis confirmed that the thermal decomposition of LSX proceeds through two distinct stages. The first decomposition stage exhibited mean apparent activation energies of 219 and 224 kJ mol ⁻¹ according to the Vyazovkin and KAS methods, respectively, whereas the second stage showed higher values of 257 and 272 kJ mol ⁻¹ . Kinetic compensation effect analysis showed superior linearity and reliability for the Vyazovkin model in determining the decomposition kinetic parameters. The COMSOL simulation predicted the onset of thermal runaway at approximately 183 °C at the center of the LSX charge after 6.89 h of slow heating. Isothermal simulations indicated negligible decomposition at 25–75 °C over 120 months, while approximately 50% conversion was predicted at 100 °C after 55 months. Under worldwide climatic conditions, the reaction progress remained on the order of 10 ^–2 in warm regions and of 10 ^–3 in cooler regions after 20 years. STANAG climatic simulations predicted conversion levels on the order of 10 ^–2 over the same period under all tested categories. These findings confirm that the LSX formulation possesses excellent thermal stability and strong long-term storage reliability under diverse thermal environments.

In the last decade, insensitive munitions (IMs) have attracted considerable attention because they offer a desirable combination of strong operational effectiveness and enhanced safety characteristics. This study explores the application of a DNAN‐based insensitive explosive composition (IEX) as an explosive filler for shaped charge devices (SCs). The IEX formulation, consisting of 35% 2,4‐dinitroanisole (DNAN), 45% 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), and 20% trinitrohexahydrotriazine (RDX), was prepared in the lab and loaded into small‐diameter SCs at different loading densities. Additionally, the influence of explosive loading density on SC jet characteristics and penetration performance was evaluated through numerical simulations and experimental firing tests. Firing tests demonstrated a positive correlation between explosive loading density and penetration depth, achieving values of 8.9, 9.1, and 10.7 cm at corresponding densities of 1.70, 1.72, and 1.74 g/cm ³ , respectively. Furthermore, the numerical predictions of penetration depths showed good agreement with the experimental results. The shaped charge jet impact (SCJI) test was performed for the manufactured SC loaded with the IEX in accordance with STANAG 4526. The IEX‐based SC did not function effectively during the SCJI test, thereby improving the munition's safety against severe threats. These findings demonstrate the potential of IEX composition for developing safer SCs capable of achieving effective penetration into steel targets.

Different explosive materials have been studied numerically and experimentally to assess the efficiency of a small diameter shaped charge in terms of produced jet characteristics and penetration depth into RHA steel targets. 26 different explosives have been simulated numerically using Autodyn hydrocode, whereas recommended explosives have been loaded into small diameter shaped charges by pressing technique and tested by static firing against RHA targets in order to validate the numerical calculations. The numerical analysis has presented an intensive global view about the variation of the shaped charge jets as a potential of the loaded explosive charge efficiencies. A successful trial has been performed to measure the shaped charge jet velocity using detonation velocity VOD 812 apparatus, where its measured value was only 3.6% different from the numerical one for HMX-V5 explosive. Besides, TITAN (L3) flash X-ray radiograph has also been implemented to explore the jet profile using the same explosive type and to measure its jet tip velocity, which has only 2.1% different from that estimated numerically. Extensive fragmentation analysis has been presented, which showed increase in both the fragment number and the fragment speed when the used explosive charge is of high detonation velocity. CL-20 explosive exhibited the largest jet tip velocity and its scaled collapse velocity was found to be 140% of TNT explosive. The calculated average fragment speed has been validated and the measured fragment speed has only 2.3% difference when compared to the SPH calculations.

The wide usage of TNT as a main charge for fragmentation shells has been eliminated due to its lower performance and exudation on the fuze thread and relevant safety measures inconvenience. These disadvantages have not become accepted anymore due to the desired safety requirements and the limited efficiency of the TNT, especially when different new explosives are introduced into researches. This research studies the fragmentation calculations of the 120 mm high explosive shell when its is loaded with different explosives rather than TNT. Different explosives have been used in the current research include the melt cast compositions such as Octol and composition B, a cast cured composition based on RDX with HTPB polymer matrix and the plastic explosive composition HMX-silicone. The fingerprint of the fragmentation pattern of each shell loaded with different explosive has been obtained using Autodyn smooth particle hydrodynamic (SPH) algorithm, whose numerical model has been validated with previous measurements using TNT explosive. Based on obtained numerical estimates, the HMX-silicone explosive has been proposed to replace the traditional TNT explosive material. This explosive has been then manufactured and casted into the studied 120 mm shell, where the experimental field pit test was established to collect, separate and analyse the resultant fragments. Current calculations and experimental results showed that the shell loaded by composition HMX-silicone produced the highest fragmentation velocities (i.e. 1.5 times that of TNT) and the largest number of fragments (i.e. 2.7 times that of TNT) with lower masses, which will be recommended for our next production stages instead of the traditional TNT.

Development of ultra-fine fiber technology and nano-sized materials are widely taking place to enhance the characteristic of different materials. In our study, a newly developed technique was used to produce improvised nano energetic fibers with the exploitation of cis‐1,3,4,6‐Tetranitrooctahydroimidazo‐[4,5‐d] imidazole (BCHMX) to spin in a polystyrene nanofiber membrane. Scanning electron microscopy (SEM) showed the synthesized nanofibrous polystyrene (PS)/BCHMX sheets with clear and continual fiber were imaged with scanning electron microscopy (SEM). Characterization of the produced nanofiber was examined by Fourier Transform Infrared (FTIR), and X-ray diffractometer (XRD). Explosive sensitivity was also evaluated by both BAM impact and friction apparatus. Thermal behavior for the synthesized PS/BCHMX fiber and the pure materials were also investigated by thermal gravimetric analysis (TGA). The results show enhancement in the fabrication of nano energetic fibers with a size of 200–460 nm. The TG confirms the high weight percentage of BCHMX which reaches 60% of the total mass. PS/BCHMX fiber was confirmed with the XRD, FTIR spectrum. Interestingly, XRD sharp peaks showed the conversion of amorphous PS via electrospinning into crystalline shape regarding the applied high voltage. The synthesized PS/BCHMX nanofiber was considered insensitive to the mechanical external stimuli; more than 100 J impact energy and > 360 N initiation force as friction stimuli. PS/BCHMX is considering a candidate tool to deal with highly sensitive explosives safely and securely for explosives detection training purposes.

The addition of some advanced additives to improve the mechanical properties of polyurethane (PU) polymeric matrix, which acts as a binder system in composite solid rocket propellants (CSRPs), is a target for the energetic materials researchers. In this investigation, 45 compositions of different crosslinked PU matrices were produced to demonstrate the effect of adding crosslinking mixture (CM) on the mechanical capabilities of polyurethane gum stock. The crosslinking mixture (CM) is composed of a triol crosslinker, trimethylolpropane (TMP), and a chain extender, 1,4-butanediol (BD). For comparison, traditional PU samples without crosslinking additives were formulated. As a prepolymer, HTPB was used with a curing agent (HMDI). The research was carried out with different ratios of TMP to BD, different curing ratios (NCO/OH=0.7, 0.9, and 1.1), and crosslinking mixture contents in the range of 0-5 wt.%. The mechanical characteristics of all the cured formulations were measured. It was demonstrated that changing the ratio of TMP to BD has a significant impact on the mechanical performance causing a wide range of elongation and strength qualities. Increasing the wt.% of triol crosslinker in the sample enhanced the tensile strength, whereas the strain has been decreased. The addition of diol chain extender increased the strain rate of the samples. The mechanical parameters were adjusted simply by employing the crosslinking ingredients to get exceptional mechanical characteristics at each NCO/OH curing ratios. Also it was concluded that PU samples of curing ratio (NCO/OH= 0.7-0.9) with TMP:BD (1:1) showed a promising results and could be used according to the requirements of the rocket system designers.