Preparation And Properties Of Modificated Combustible Cartridge Cases By Fibers

Combustible cartridge case was a kind of porous composite energetic materials, with dual roles of the container and the energy component. There were no back shells and salvage-shells problems with combustible cartridge case. Using combustible cartridge could reduce the weight of ammunition to increase the bombs loading weight, improve artillery operating conditions and shooting speed, and reduce the arduous task of recovery and transportation. The manufacturing process of combustible cartridge case was simple and low cost, and easy for fast and stack production in wartime. It also saved lots of precious metal materials. The combustible cartridge had resulted in the improvement of artillery and the modular charge system. But the porous structure also led to a contradictionary problem between mechanical properties and combustion properties. Accompanying with the modern high-velocity weapons and modular charge technology improvement, higher standards of combustion performance and mechanical properties of the combustible cartridge were required.This thesis studied the way of improving the combustion performance of combustible cartridge by increasing the content of energetic components. A novel energetic fiber have been designed and manufactured in this thesis. This novel energetic fiber could improve the combustion performance of combustible cartridge and it also had strengthing effect,. Series of modified combustible cartridge had been designed and manufactured by using this novel energetic fiber as strengthing components. As the adding amount of energetic fiber increased, cartridges oxygen balance greatly improved, and enthalpy of formation of combustible cartridge increased. The improvement of energy levels was theoretically beneficial to the improvement of combustion performance.The microstructures of modified combustible cartridge cases were investigated by gas adsorption and desorption analyzer, mercury instrusion porosimeters (MIP) and electron microscopy. Pores of cartridge case were mainly slit-shaped and wedge-shaped. The fractal model of pore structure of combustible cartridge cases was established by virtue of the fractal geometry, through combining Menger sponge with MIP test. The backbone fractal dimension (DH) was formed by the component's space and influenced by the amount and size of components; percolation fractal dimension (Dv) represented the pore structure of components themselves.Mechanical properties, combustion performance and moisture adsorption of modified combustible cartridge cases have been studied through materials mechanics testing machines, closed-bomb tests and temperature-humid alternating tests, respectively. The influences of different component content, test conditions and other factors on combustion properties of the combustible cartridge have been deeply studied. Compared with basic formula B combustible cartridge, the compression strength and tensile strength of formula PNF9 which added 9% energetic fiber increased 6.8% and 17.2%, respectively. As the energetic fibers adding amount increased, combustible cartridge mechanical performance declined.In constant-volume combustion, the burning-off time and impetus of formula PNF9 which added 9% energetic fibers were 5.45ms and 590.8J/g, respectively. While, the burning-off time and impetus of basic formula B were 7.63ms and 536.9 J/g. As the energetic fiber content increased, gas generation rate boosted and burning-off time shortened, combustion performance improved. The charge simulation test revealed that adding energetic fibers could also reduce the solid residues and combustible gases.In constant-volume combustion experiments, as loading density increased, the gas generation rate of combustible cartridge became faster, the combustion became more effective, cartridges energy released more complete. The impetus tested under 0.12 and 0.16 g/cm3 loading densities was 583.9 J/g, while it was 602.8 J/g under 0.16 and 0.20 g/cm3 loading densities. With the ignition power increased, the burning rates were accelerated, cartridges energy release were more complete. Under 0.12 and 0.20 g/cm3 loading density, impetus improved form 590.8 J/g of weak-ignition to 672.5 J/g of strong-ignition.The porous structure and component materials strongly affected the moisture adsorption of combustible cartridge. Moisture adsorption rate of formula B cartridge reached 3.91% under 20℃and RH80%. After adding 16.5% energetic fiber, moisture adsorption rate dropped to 3.43%. The gas generation rate decreased significantly after adsorpted moisture, and became more volatile in lower loading density. Under 0.20g/cm3 loading density, the burning-off time of combustible cartridge with 1.6% moisture extended from 6.64 ms of dry sample to 12.02 ms.