Combustible Cartridge Case Research Articles

Non-destructive evaluation of artillery combustible cartridge case using terahertz radiation

In this study, terahertz radiation was employed to determine the radius, diameter, and thickness of the nitrocellulose combustible cartridge case used for tank ammunition. The construction of the sample was outlined, and the refractive index of the case material was measured. A terahertz rotary scanner with a time-domain spectroscopy setup in reflection configuration was developed, and its performance and parameters were determined. A wire polariser was introduced as a reference to determine the stable time difference. The radius and diameter measurements of the case were based on a reference terahertz pulse reflected from its metal base. The thickness of the case was calculated based on the time difference between pulses reflected from its inner and outer surfaces. These measurements were in agreement with the reference measurements. The results prove that the developed setup and measurement methods are suitable for the non-destructive evaluation of cases and provided satisfactory performance.

Interior ballistic two-phase flow model and its calculation for a mixed charge structure

The mixed charge for guns generally consists of two or more kinds of propellants. Medium and large caliber guns usually adopt the typical combination of tubular and granular propellants, not only meeting interior ballistic indexes but also improving launch safety. However, numerical investigations, charge design, and optimizations of such charge structures rely heavily on classical interior ballistic theory. To gain insight into some crucial phenomena in this complex interior ballistic process, a two-phase flow dynamic model of a 125 mm smoothbore gun with mixed charge (granular propellants, tubular propellants, and a combustible cartridge case) is developed. Unlike the previous form of solid governing equations, the conservation equations, surface temperature and combustion law functions are simultaneously established. The space-time conservation element and solution element (CE/SE) method is used to solve the mathematical model, simplifying the calculations of partial derivatives in source terms. Results show that the model can describe the combustion and flow, and the predicted projectile velocity agrees well with the measured one. In addition, the effects of the mass ratio of mixed propellants on interior ballistic performance are discussed in detail. As the tubular propellant mass decreases, ignition consistency deteriorates, particle accumulation intensifies, and the maximum pressure exceeds the permitted one, all of which may affect launch safety. The work in this paper provides a powerful tool for observing and predicting the interior ballistic process of the mixed charge.

An Autonomously Self‐Healing Silicone Polyurea Waterproof Coating for Combustible Cartridge Cases

AbstractNitrocellulose‐based combustible cartridge case (NC‐3C) is highly hygroscopic, which greatly limits its broader application. The effective strategy for NC‐3Cs to prevent moisture is the endowment of waterproof coatings. However, the traditional waterproof coatings for NC‐3Cs cannot self‐heal the inevitable mechanical microcracks suffered during handling and storage, which often gives moisture much more opportunities to destroy the internals. Therefore, it is necessary to develop a self‐healing waterproof coating for the protection of NC‐3Cs. Herein, a smart self‐healing silicone polyurea (SPU) elastomer based on dynamic reversible hydrogen bonds is designed as a waterproof coating for NC‐3Cs. The SPU elastomer shows an outstanding self‐healing efficiency of 99.06 % after 12‐hour self‐healing at room temperature. And it also can self‐heal its damages even when the ambient temperatures rise to 50 °C or drop to −18 °C. Moreover, the SPU‐coated NC‐3C can also self‐heal its microcracks in time after being scratched and obtains extremely low water absorptions (<0.20 %) after 24‐hour soaking, exhibiting good waterproof performance. Endowing the waterproof coating with self‐healing ability is a promising design strategy to repair the coating microcracks and improve the environmental adaptability of NC‐3C during handling and storage. This work pioneers a new design of self‐healing waterproof coating for NC‐3Cs, and it has a positive guiding significance to expend broader application of NC‐3C.

Specificity of Burning of Porous Combustible Material Used as Cartridge Case

The combustible cartridge case has become an integral part of many modern weapons systems. The energetic and burning characteristics of the combustible case can have a significant impact on shot parameters. This paper describes Closed Vessel Tests (CVTs) performed on combustible cartridge case material and presents a method of determining the physical burning law and the linear burning rate of the tested material. The method was verified on the basis of the results of CVT of the felted combustible cartridge case material of a 120 mm tank round. It is shown that, in the case of porous combustible materials, the standard methods of determining the burning rate fail. The porosity of combustible materials greatly increases the burning surface and heat feedback from the burning zone to the unburned structure. These effects significantly increase the burning rate of porous materials. The results of analysis show the strong dependence of the burning rate on pressure. The results of this study can be applied in the modeling of gun propellant systems that contain combustible case elements.

Composition optimization and characterization of combustible cartridge cases with polyvinyl acetate (PVAc) as a binder

Combustible cartridge case samples composed of nitrocellulose (NC), polyvinyl acetate (PVAc), kraft cellulose (KC), dibutyl phthalate (DBP) and diphenylamine (DPA) were prepared to study their structures and chemical and mechanical properties. Taguchi’s experimental design method was used to design the experimental formulations. First, simultaneous thermogravimetry-differential scanning calorimetry (STA TG-DSC), scanning electron microscopy (SEM), Brunauer–Emmett–Teller analyser (BET), bomb calorimeter (BC), vacuum stability tester (VST) and a tensile testing machine (TTM) were employed to analyse the thermochemical characteristics, structure, explosion heat, chemical stability and compatibility, and mechanical strength of all formulated samples. Based on the analysis results, the weight loss of the combustible cartridge case sample obtained by the TG experiment was chosen as the quality characteristic. The results of the Taguchi analysis indicated that the optimal parameter combination was an NC/KC weight ratio of 80:20, an NC/PVAc weight ratio of 85:15, an additional DPB of 3.5 wt.% and a density of 1.25 g/cm3. The results of the chemical stability and compatibility test, explosion heat test and mechanical strength test show that the test samples prepared with the optimal parameter combination can meet the requirements of combustible cartridge cases. Furthermore, the combustion performance of the combustible cartridge case sample prepared with the optimal formula was measured by a high-temperature combustion furnace (HTCF) and burning rate measurement device (BRM). The experimental results indicated that the autoignition temperature and ash content were 231 °C and 0.28%, respectively. In addition, the burning rate increased with increasing combustion chamber pressure but was lower than that of ordinary gun propellants at the same pressure. These combustion characteristics can meet the quality requirement of combustible cartridge cases. Finally, an actual combustible cartridge case was prepared and verified. The result of the performance verification test indicated that the average ash content was 0.30%, which was similar to that of the previous test samples and met the quality requirement.

Improvement in High Temperature‐Resistant Performance and Waterproof Property of Combustible Cartridge Case with BEMS Resin Based Composite Coating

AbstractCombustible cartridge case (CCC) is an important charge component which is very suitable for the weapon systems that need light load. It is a kind of nitrocellulose‐based porous material which has a low ignition temperature and strong hygroscopicity. Thus, if the surface of the CCC is not protected very well when it is used in modern weapon with faster fire rate, it will be easy to self‐ignite in the high‐temperature gun barrel and absorb moisture in a high‐humidity environment. These problems will worsen both the safety of gun operators and the combustion performance of CCC. However, they are not solved well by current research and industrial practice. Herein, we designed a new composite coating which can improve both the high temperature‐resistant performance at a higher temperature and waterproof property of CCC. The boron nitride (BN) and epoxy resin were used to modify silicone resin. The BN and epoxy modified silicone (BEMS) resin, inorganic adiabatic fillers and other additives were mixed together to prepare a BEMS resin based composite coating solution, and then the solution was sprayed on the surface of the combustible cartridge case to form a protective coating. The chemical structure of BEMS resin was investigated by FTIR. The thermal stability of coating films was analyzed by TGA. The high temperature‐resistant performance, water contact angle on the surface and waterproof property of the coated CCC were analyzed by muffle furnace experiment, water contact angle tester and immersion test, respectively. Results show that boron nitride and epoxy resin were successfully grafted on silicone resin chains. Compared with control samples, the thermal decomposition rate of the prepared coating films is significantly reduced. The coated CCC will keep 108.8 seconds while not burning at 230 °C. The heat resistant time increased by 16.74 % at 230 °C. The water contact angle on the surface of the coated CCC can reach 105.71° which was improved by 67.01°. After being soaked for one hour, the water absorption of the coated CCC is reduced by 96 % in distilled water and by 99 % in 3.5 wt % of sodium chloride solution. Compared with most present coatings, the new BEMS resin based composite coating which we designed can improve both the high temperature‐resistant performance and waterproof property of the CCC significantly and effectively. It provided a new way for study on the protective coating of CCC.

Insensitive High Explosives: V. Ballistic Properties and Vulnerability of Nitroguanidine Based Propellants

AbstractThis paper reviews the ballistic properties, stability and vulnerability of gun propellants, gas generators and rocket propellants containing nitroguanidine (NGu), CAS−No [556‐88‐7] as an energetic filler. Nitroguanidine and its formulations burn stable over a broad pressure regime extending from subatmospheric to high pressures (0.1 kPa–400 MPa). Its high nitrogen content (53.83 %) and oxygen balance (Ω=‐30.75 %) effects a high gas pressure in gun propellants combined with low explosion temperature and consequently low signature and reduced erosion. NGu is an effective stabilizer for a broad array of energetic materials encountered in gun and rocket propellants including AP, ADN, HMX, RDX, NGl and also materials with low thermal stability such as NC, HNF, TNAZ and ADN. Finally, the low vulnerability of NGu‐based propellant formulations makes them taylor made to serve insensitive munitions. This review covers 31 NGu‐based rocket and gas generating propellant formulations, 44 gun propellants, five of which contain guanylurea dinitramide, (GuDN, FOX‐12), CAS−No [217464‐38‐5] for comparison, four reference propellants containing neither of the aforementioned ingredients and six combustible cartridge case formulations based on NGu. In addition, the combustion properties of pure NGu, pure GUDN and NGu modified with 17 different catalysts are revised. The review contains 142 references from the public domain.

Constant-volume combustion performance of mixed charge of foamed propellant with nitramine propellant

Foamed propellants based on polymer bonded nitramine explosives show high burning rates due to their porous structure and showed great potential for combustible cartridge case. Thus, the in-depth study of the co-combustion behavior of the foamed propellant and matching propellant is necessary. In this paper, closed bomb tests were used to study the co-combustion performance of nitramine propellant (RGD7) and surface coated nitramine propellant (SC-RGD7) mixed with foamed propellant. The influence of foamed propellant’s proportion in mixed charges on the combustion behavior was studied and analysed. It was found that the maximum dynamic vivacity and the value of B at maximum dynamic vivacity of mixed charge increased with the increase of added foamed propellant, resulting in better combustion progressivity. Meanwhile, the ignition delay of foamed propellant influenced the first stage of combustion, and the penetration combustion of foamed propellant influence the middle stage.

A comparative study of combustible cartridge case materials

Foamed combustible material based on polymer bonded RDX was fabricated using CO2 as foaming agent. The inner structures of felted and foamed combustible materials were presented by SEM. The two materials presented different formulations and inner porous structures. The combustion behaviors of felted and foamed materials were investigated by closed vessel test. Simultaneously, the co-combustion behavior of combustible cartridge case with 7-perf consolidated propellants was also investigated. The results of closed vessel test is applicable to gun system which is made of the foamed combustible material as component.

Determination Methods for Storage Stability of Combustible Cartridge Case

The stabilizer content of aging combustible cartridge case (CCC) was measured by gas chromatography and chemical method. And the test results under different experimental conditions were analyzed. The results showed that the stabilizer content of the CCC decreased gradually with the aging time increased, which is in line with changes of stability of CCC. It is feasible to determine CCC stability by using gas chromatography.

Influence of Humidity on Burning Perfectibility of Winding Combustible Cartridge Case

Studied the hygroscopic properties of winding combustible cartridge case by weighing method. Investigated residue formation of cylinder materials with different water contents by nitrogen-bomb tests. The results show that the higher the relative humidity is, the greater the equilibrium moisture content of the inside-wall material is. When the relative humidity was about 90%, its absorption rate was about 4.3%. Compared with its outside wall, the inner parts have much stronger moisture absorption properties. And the gross of combustion remains reached to the minimum when the relative humidity was about 60%.

Alkaline Hydrolysis of Resin-Based Combustible Cartridge Case and Application of its Hydrolysate as Crop Fertilizer

AbstractDisposal of hazardous and toxic waste arising out of combustible cartridge case (CCC)–based explosive munitions is an environmental issue of global concern. A large quantity of CCC waste is disposed of by open burning or detonation because there is no viable waste-disposal technology that is environmentally friendly and is found suitable for bulk treatment available at present. In the present study, the process of alkaline hydrolysis of CCC composition has been studied. It is found that CCCs waste can be suitably treated and neutralized by a simple chemical process (alkaline hydrolysis) that is eco-compliant. It is possible to recover a high proportion of nitrogen (87%) from this waste. The CCC hydrolysate can be suitably used as fertilizer for crop. Pot culture studies carried out using the hydrolysate as a fertilizer on wheat seed and plant give encouraging results of the main crop performance parameters like plant biomass, yield, plant growth, and chlorophyll content.

The Influence of Humidity on Burning Perfectibility of Molded Combustible Cartridge Case

Studied the hygroscopic properties of a molded combustible cartridge case by weighing method. Investigated residue formation of cylinder materials with different water content by nitrogen-bomb tests. The results show that the higher the relative humidity, the greater the equilibrium moisture content of the inside-wall material. When the relative humidity was about 90%, its absorption rate was about 5.4%. Compared with its outside wall, the inner parts have much stronger moisture absorption properties. The combustion remains grew in quantity generally with the increase of moisture content.

English

Several combustible cartridge case (CCC) formulations containing nitrocellulose (NC) as anenergetic ingredient with diphenylamine (DPA) as stabiliser, cellulose fiber as reinforcing materialand polyvinyl acetate (PVAc) as a binder are processed to form combustible discs. A formulationcontaining nitrocellulose (83 parts), cellulose (17 parts) , PVAc (20 parts) and diphenylamine(1 part) by weight was observed with the improvement of mechanical properties without anyadverse effect on combustion characteristics, safety parameters and compatibility with triplebase multi-tubular propellant. Dynamic firing performance was also satisfactory.

Combustible cartridge case formulation and evaluation

Abstract The formulation of combustible cartridge case was studied by changing the percentage of ingredients namely; nitrocellulose (NC), nitroguanidine (NiGu), cellulosic fibres, dibutylphthalate (DBP) and diphenylamine (DPA). A composition containing around 55% nitrocellulose & balance cellulosic fibers and nitroguanidine along with 3.5 parts dibutylphthalate & 1 part of diphenylamine was found compatible with triple base multi-tubular propellant, besides having reasonably good mechanical and ballistic properties.

Determination of Nitroester and Stabilizer Migration in combustible cartridge case wall

AbstractPropellant nitroesters (diethyleneglycol dinitrate and nitroglycerin) and stabilizer (Akardite II, N‐methyl‐N,N′‐diphenylurea) were determined in combustible cartridge case (CCC) wall specimens from 120 mm M829 rounds which had been exposed to elevated temperatures in environmental chambers or which were returned from deployment in Southwest Asia. The results suggest that the migration of these components from the propellant is uniform about the circumference of the adhesive joint between the CCC body and adapter but not longitudinally above and below the joint. The accumulation appears to be linear with time of exposure, with both nitroesters migrating at approximately the same rate with similar energies of activation. The conventional sampling and analysis method is compared with a new micro‐sampling and analytical method which reduces solvent waste and extraction time, and considerably reduces damage to the rounds from removal of the analytical specimen.

Hazard Assessment for Manufacture of Combustible Cartridge Cases using Picrite

A systematic study of the effect of impact, friction, flame and electric spark sensitivity was carried out on the samples combustible cartridge case (CCC) withdrawn at different stages of manufacture. These are Stage I dried felted CCC; stage II-CCC from stage III Coated with nitrocellulose coating. based on the results obtained from various experiments, the CCC can be classified for handling storage and transportation as Group 3, for safety distance category as UN 1.3 and for fire fighting as class 2. further it is concluded from hazard analysis study that the CCCs are safe to handle but these should be protected from naked flame.

Cook Off Study of Combustible Cartridge Cases

Combustible cartridge case (CCC) offers specific advantages over the conventional metallic (brass) case. The CCCs are made of cellulose fibres with suitable explosives to ensure debris-free combustion inside the gun barrel. The presence of explosives in CCC, however, causes increased vulnerability to cook-off. An experimental study of cook-off of CCC was carried out by hot plate technique. Cook-off data for CCC of different compositions and with various cook-off delay coatings was measured. It was found that out of four types of coatings, two gave better results.