مجله تحقیق و توسعه مواد پرانرژی
سال دهم شماره 3 (پیاپی 24، زمستان 1393)

Experimental evidence shows that some nano-composites have particular importance in armor vehicles structures. Simulation and finding the properties of these Nano-composites analytically or numerically is an essential work, due to the cost of nano reinforcements and their production complexity with current methods. This paper employs analytical- experimental constitutive equations of energy absorption in composite nano-armors and various approaches for using in nano-armors simulation. In these studies, the constants values required for numerical simulation are obtained by the experimental tests. So, considering these constants can be extracted from molecular dynamics simulations, the use of finite element method combined with molecular dynamics simulations its essentials in these simulations.

Guanidine and its derivatives have wide applications in various industries and energetic materials. Because of these wide applications, various researches are concentrated on the synthesis of guanidine and its derivatives. This review article has introduced synthesis methods of guanidine and its derivatives. Guanidine synthesis routes like addition of ammonium salts to cyanoguanidine or cyanamide, and thiourea reaction with ammonium salts are studied. Synthesis methods of nitro-, nitroso-, amino-, and alkyl- guanidines are reviewed. Also, different applications of guanidine and its derivatives in the field of energetic materials are summarized.

Recent studies in solid composite propellants indicate that acceleration field cause to increase in burning rate. Relation between acceleration field and burning rate of propellant have an important effect on missile systems ballistic, especially on perforated grain missiles. If these effects has neglected in design phase, the pressure-time profile shifted out of acceptable rage and result in increasing pressure and motor fail. Therefor in order to design rockets, need to know the acceleration effect on solid rocket performance. In this work influence of acceleration field in burning rate of non-aluminized and aluminized propellant has been investigated. The results showed that at both of them, the spin acceleration led to increase the burning rate of propellants. Also models with a good accuracy to predict the performance of propellant in accelerated field, has been introduced.

HTPB based composite Solid propellants are the source of power for the propulsion of rockets and missiles. Since composite solid rocket propellants, used in rockets and missiles is the fastest degrading component of the complete system, shelf life of the system is mainly governed by the life of the propellants. During storage and transportation, the propellant grains are subjected to various conditions such as humidity, temperature, vibration, and shocks. This condition causes significant changes in mechanical properties of the propellant. In this paper the effects of parameters such as particle size of metallic fuel, grain shape, temperature, humidity and migration on the aging composite solid propellant was studied. The Investigations showed that the Nanoaluminum (nano vs micro) is very susceptible to ageing phenomena. The free standing grains have less aging than case-bonded grains. In general, the temperature, humidity, plasticizer migration and gaseous diffusion have negative effects on the chemical and physical properties of propellant.

Thermal insulation materials protects internal surface of the motor casing in contact with the hot produced gases, extreme turbulence flow and high pressure due to combustion propellant. Insulation Materials in the rocket motor covers the inner surface of the motor casing and protect the body against the damage caused by extreme and short-term heat, intense turbulent flow and high pressure. One of the characteristics of this material is ablation upon which the insulation are classified in two categories, ablating no-charring insulations and ablating charring insulations or composite insulation. Composite insulations are consisting of resin or elastomer matrices with reinforcing phase. These matrices can be pointed to resins such as phenolic resins, epoxy, polyester and polyurethane elastomers, rubber, Nitrile and Silicone that reinforced by the suitable reinforcing such as Fibers, graphite, silica, carbon, quartz, glass, asbestos, etc. Flame retardant additives also have a large influence on the thermal properties of insulation among these can be noted the antimony oxide, organic halogenated compounds, molybdenum, metal hydrates and inorganic halides. In this paper, the properties of each of these compounds are examined. Also, the thermal properties of an insulating epoxy based composites with and without flame retardant suggests delayed of curing process, Submit a uniform pressure – time curve and increase the amount of residual charcoal in the composite insulation have been flame retardant.

Polyurethanes are the most well-known polymers used as a binder in high energy material. Polyurethanes are generally synthesized by the reaction of diisocyanates, polyols and a chain extender. Polyurethane elastomers have a two phase morphology consisting of hard and soft segments. Chain extenders are small diols or diamines that are inserted to the hard segment of polyurethane chain. Chemical structure of chain extender, the amount of chain extenders in polyurethane and processing condition can change the morphology and properties of the polymer through influencing on the intermolecular attractions between hard-hard and hard-soft segments of polyurethane. In this paper, the role and impact of various chain extender on the physical, mechanical and energetic properties of the thermoplastic polyurethane were investigated.

The design of cryogenic propellant tanks that are used for storing liquid hydrogen and liquid oxygen due to the low boiling temperature has many differences compared with the others.In this paper, the most important insulated systems in cryogenic storage tanks, such as vacuum insulated, vacuum insulated with powder, vacuum insulated with radiation shields, multilayer super insulation and vacuum cooled shields are discussed. Researches have shown that due to the kind of application and capacity of the storage tanks, the kinds of appropriate insulations couldbe difference.The most appropriate type of insulated tanks that are used in small-scale units is vacuum cooled shield, and multilayer super insulation is used in cases that the weight of tanks has an important role. Also vacuum insulation is the most appropriate option for a high volumeliquid oxygen storage tanks.