Terminal Ballistics Research Laboratory

We report two energetic metal coordination polymers (CPs), [Zn(Hbtm)2]n (1) and [Cd3(btm)2Br2(H2O)2]n·4H2O (2), based on the bis(tetrazole)methane (H2btm) ligand. SCXRD analysis shows that 1 forms a 2D layered structure extending into a 3D supramolecular network via hydrogen bonding, while 2 features a 3D framework. Thermal analysis indicates that 1 is stable up to 330 °C, while 2 remains stable up to 395 °C after losing water molecules at 126 °C. Complex 1 exhibits a detonation velocity of 7.46 km s-1 and a detonation pressure of 26.16 GPa, whereas 2 exhibits values of 6.02 km s-1 and 12.50 GPa, respectively. Both complexes are insensitive to impact (>40 J) and friction (>360 N). The kinetic parameters were determined using the Kissinger and Ozawa methods, and the results are in good agreement with those obtained from the ASTM-E698 method. Additionally, both complexes catalyze the thermal decomposition of ammonium perchlorate (AP). Owing to its high thermal stability, comparable to that of TATB and other H2btm-based complexes, 1 is a promising candidate as a heat-resistant explosive, while both complexes show potential for application in advanced energetic formulations.

Fragmentation warheads are considered critical components of missiles and other air-delivered weapon systems used against ground and aerial targets. The study of the terminal effects of a fragmentation warhead is an essential requirement during the design stage, layout configuration during the experiments, and development of protective system configuration against it. A Monte Carlo simulation-based computational model, named the Munitions Lethality Analysis (MULAS), has been developed to assess the terminal effects of the Pre-Fragmentation (PF) warhead in terms of its lethality and blast. A parametric study was conducted on cylindrical PF warheads with steel balls as a kill mechanism using the MULAS simulation method. The effect of the size of fragment steel balls on both fragment spatial distribution and warhead lethality, and the impact of the initiation point on warhead lethality, have been studied. Experiments with cylindrical model PF warheads were performed to validate the MULAS methodology. The test data analysis revealed that the performance prediction for fragment lethality and blast using the MULAS methodology was in fair agreement with the experimental data within a 10 % variation.

Abstract Penetrating projectile injuries from bullets and fragments remain a leading cause of casualties in modern warfare. Understanding the mechanical interaction of these projectiles with biological tissues is crucial for designing and optimizing both modern ammunition and protective systems. Toward this end, we review the mechanics of the interaction of the projectiles with various biological tissues. The review focuses on the relationship between projectile characteristics (velocity, shape, design), specific tissue, and the resulting injury. The aim is to understand the relationship between these factors and the energy or energy density required to inflict specific tissue-specific injuries. The review highlights the distinct failure mechanisms for each tissue for bullets and fragments. Skin failure is manifested by a combination of crushing, shearing, and elastic hole enlargement. Bone fracture predominantly shows conical cavity formation and associated radial and concentric cracks. Muscle and brain failures involve shearing and temporary cavity formation. Eye, due to its delicate nature, is highly susceptible to penetration by small projectiles with minimal compression. The data suggests significant variations in the energy density needed for perforation depending on the tissue type and projectile characteristics. For example, skin perforation requires a lower energy density (0.1–0.2 J/mm2) compared to bone (0.05–3.2 J/mm2). Further, the traditional 80 J energy criteria of a projectile for defining the lethality threshold might be overly conservative, especially for smaller projectiles. This review also highlights the importance of considering energy density as casualty criteria.

This paper describes preparation and characterization of hydroxyl-terminated polyester (HTPE)-based energetic composites from high melting explosive (HMX) and polyester polyols by varying the amount of polymer binder content by cast cured technique. These composites possess several advantages, such as improved structural integrity, higher thermal stability, and a lower sensitivity when compared to TNT-based formulations. They are employed in various modern armaments, including bombs, missile warheads, and torpedoes.The HTPE prepolymers were cured with different curing agents to crosslink HTPE-based energetic composites. The effects of the different curatives on the chemical, thermal, mechanical and energetic properties were studied by employing different analytical instrumental techniques. The chemical stability assessed using a vacuum stability tester (VST) demonstrated significant high chemical stability. The hazard assessment in terms of the impact and friction sensitivity indicated that all energetic composites were less sensitive than those of pure HMX and slight varying in the sensitivity, depending on the curing agents. The thermal stability is either comparable or higher than that of the HMX. The compression strength of the HTPE-based composites was studied and found to be increasing with increasing the polymer content. The varying proportions of HMX and polyester were carried out to see the effect on the crosslinked elastomeric binders on the mechanical properties. The detonation velocity was obtained in the range of 7.0 km/s - 7.9 km/s with varying amount of the binder system from 10 % - 20 %.

Abstract Aluminum foams find extensive applications in the automotive, marine, and defence industries, owing to their exceptional properties like high specific strength and the ability to absorb energy effectively under constant stress. In the current study, the aluminum composite foams (ACFs) reinforced with different wt% (n=2,4,6,8 and 10) of B4Cp (21-30µm) have been developed by stir casting method and their compressive properties at quasi-static (0.001s-1), intermediate (1s-1) and dynamic loading (680s-1) have been investigated. The study shows that adding B4Cp up to 8wt% initially increases foam expansion and cell size, followed by a decrease, while relative density and cell wall thickness exhibit the opposite trend. At all tested strain rates, the compressive properties such as peak stress, average plateau stress, and energy absorption capacity show a consistent increase with the rise in B4Cp wt%. The density normalized average plateau stress confirmed the strengthening effect due to B4Cp addition in the foam. The developed aluminum foams exhibit strain rate sensitivity in their average plateau stress.

ABSTRACT RDX/HMX-TNT-based aluminized explosive compositions have been investigated to find empirical relations based on heat of explosion (Q) and velocity of detonation (VOD) for calculation of peak over pressure (POP) and impulse (I). Four HMX-TNT-based aluminized compositions have been selected based on calculated values of Q and explosive power. Explosive charges of RDX/HMX-TNT-based aluminized compositions and TNT have been prepared by melt-cast technique for measurement of VOD and air blast. Cylindrical explosive charges with length to diameter ratio of ~ 1 and weight ~ 1.3 kg have been used for measurement of pressure-time profiles at standoff distance of 2–6 m. Similar measurements were also performed for the explosive charges of TNT of weight ~ 11 and 17 kg. Normalized values of Q and VOD 2 with corresponding values of TNT have been used to compute charge weight for calculation of scaled distance which is termed as normalized scaled distance. Form of empirical relations has been decided from variation of POP and I with normalized scaled distance. Values of constants used in these relations have been determined using regression analysis. Validation of empirical relations has been carried out by comparing calculated and experimental values of POP and I for explosive charges.

This study explores the development of energetic coordination polymers (CPs) based on the atrz and HDNBA ligands through mixed-ligand strategy resulted in reduced sensitivity while maintaining the significant energetic performance.