ABSTRACT Aircraft fuels, called jet propulsion, are used in several areas of activity within aeronautics. There are jet fuels based on kerosene, that is, those obtained commercially, and there are synthetics produced in the laboratory. All of these fuels are included within the so-called propellants. In this article, Jet propulsion-8 (JP 8) fuel was used as the basis for data analysis, and thus two temperature ranges were analyzed. The first range, from 300 to 2500 K, was analyzed for specific heat, enthalpy and entropy. Based on theoretical and experimental data, artificial neural networks (ANNs) were developed to identify these properties in other working conditions, that is, at other temperatures.

The combustion process of triethylaluminum is investigated by means of reactive molecular dynamics simulations using the ReaxFF force field. The behavior of the system in five different temperatures ranging from 2000-4000 K was evaluated. As a pyrophoric material, TEA reacts also with water, generating gaseous hydrogen, whose content increases with the system temperature. Rapid water formation and O2 depletion were observed and, using Arrhenius equation, the preexponential factor and activation energy were found to be 9.67E+09 s-1 and 1.242 kJ mol-1, respectively. The results obtained are in accordance to the expected for pyrophoric materials and the simulation in question can help elucidating and analyzing the complex reaction mechanism of TEA combustion.

Prediction of chemical explosions parameters is an important step for blast tests for civil and military applications. Applying computational chemistry and experimental results, this paper presents the decay rate of pressure in air from the epicenter of 2.70 kg of PBX-Plastic bonded explosive detonation to the distance of 2.0 meters. Pressure in the epicenter was calculated using reactive molecular dynamics simulations and the incident pressure at 1.3; 1.6 and 2.0 meters were measured with piezoelectric pressure sensors. The explosive for the full-scale test were non-confined in a cylindrical shape. Results of simulation and recorded values were consolidated and the rate of pressure decay was verified by statistic regression. Good agreement was verified between computational and experimental pressures data. This research can help designers to prepare protection devices in test areas, storages of explosives or important buildings for military proposes.

Magnesium/PTFE/FPM decoy flares, also named conventional flares, were designed in order to protect combat aircraft from the threat caused by infrared-guided missiles. Adverse storage or transport conditions may cause reactions that deteriorates chemical properties of the conventional flares, causing the aging and compromising its performance. The aim of this article was to characterize the influence of accelerated aging on conventional flares. The study was performed with the latest lot of conventional flares from Brazilian Air Force, subjected to 50 days exposure in a climatic chamber at 76 °C and 62% RH. Upon completion of the accelerated aging process, samples of aged conventional flares were compared with unaged material. Qualitative determination of chemical species present was carried out using the techniques FT-IR and SEM/EDS. Magnesium hydroxide, the main product of aging process and primary aging indicator on conventional flares performance, was determined using thermogravimetric analysis and the amount was correlated with results of the experimental techniques Density Determination, Calorimetry and Vacuum Stability Test. Formation of additional magnesium hydroxide mass, that increased 100% during the aging process, caused the passivation of magnesium, compromising the combustion process and making the composition less energy efficient, as verified in the results of the calorimetric tests.

Epoxy resins are an important class of thermostable polymers, widely used in structural applications or as adhesives. However, the low fracture resistance is their main weakness in many applications. Due to this fact, this study aims to modify a polymer matrix based on a novolac epoxy resin with an organo siloxane (AMS). The final properties of cured epoxys resins are affected by the curing process and the coatings modified in this study with AMS and cured with acid catalyst presented greater resistance to thermal decomposition compared to that cured with Aradur, demonstrating a higher content of crosslinking in the siloxane polyether and the novolak epoxy resin chains. This epoxy matrix modified was used to prepare coatings whose films applied to 1020 steel surfaces presented a resistance of 1010 Ohm-cm-2. This resistance value is one order of magnitude greater than that of epoxy resins films modified by siloxanes in published studies, which demonstrates a potential economy in terms of maintenance costs of metal structures and machines used in power plants (UTE). To obtain the developed inks in pilot plant scale, it was used an aromatic polyamine as curing agent, characterizing the product obtained as an epoxy bi-component paint for commercial use.

This article aims to estimate the shelf life of the PBX by thermal analysis estimated by the Arrhenius equation, equivalent to the time of storage at accelerated aging. The PBX was subjected to accelerated aging in an oven at controlled temperature 60 ºC for periods of 5, 10, 15 and 25 weeks, which are equivalent to 5, 10, 15 and 25 of natural aging, respectively, at a temperature of 25 ºC. The curves of thermal decomposition of the samples were obtained by the DSC (Differential Scanning Calorimetry) technique. The kinetic parameters, such as the activation energy and pre-exponential factor, were determined by the Ozawa method and the Kissinger method. Initial results of this study indicated that, for a period of 25 years of storage in the cargo hold, the material did not change this aging significantly. To study the life of PBX analyzes, vacuum chemical stability were also conducted to verify the safety of explosive handling.

ABSTRACT The application of fluoropolymers in highenergy-release pyrotechnic compositions is common in the space and defense areas. Pyrotechnic compositions of magnesium/Teflon/Viton are widely used in military flares and pyrogen igniters for igniting the solid propellant of a rocket motor. Pyrotechnic components are considered highrisk products as they may cause catastrophic accidents if initiated or ignited inadvertently. To reduce the hazards involved in the handling, storage and transportation of these devices, the magnesium/Teflon/Viton composition was subjected to various sensitivity tests, DSC and had its stability and compatibility tested with other materials. This composition obtained satisfactory results in all the tests, which qualifies it as safe for production, handling, use, storage and transportation.

ABSTRACT This paper describes the polycarbonate acrylic laminated development that can be applied in aeronautics and aerospace transparencies. The case studied is a laminated double-curved transparency (bubble form) used in an observation side window of a military aircraft. Side windows need strength and specific characteristics, similar to windshields, allowing the perfect visualization and image capture. Laminated transparencies composed by different materials have better qualities than the monolithic ones. This kind of transparency can offer high mechanical and chemical resistance, high transparency, no fragmentation and easy maintenance or recovery. A significant amount of information about materials and processes was jointed in order to build the reinforced transparency and validate this study. The final results were analyzed based on two points of view: mechanic resistance and, especially, optical quality.

The aim of this work was to synthesize a polyurethane polymer matrix using polyols as a raw material to obtain a binder such as the hydroxyl terminated polybutadiene (HTPB) pre-polymer in energetic material formulation. The soybean-based polyol was the best starting raw material for producing a binder for solid fuel formulation in rocket motor applications. Characterization of the obtained soybean-based polyurethane binder was carried out by employing FT-IR analysis and thermo analytical techniques that showed similar HTPB binder thermo decomposition behaviors, confirming their potential for use as polymer matrix composites.

Composite solid propellants prepared with HTPB prepolymer - Hydroxyl Terminated Polybutadiene, AP - Ammonium Perchlorate as oxidizer and aluminum particles as an additive metal, have characteristics of high electrical resistivity. The loading process of the polymer matrix did not obtain homogeneity, resulting in clusters, mainly of metal particles. The effect of clustering in the composite was studied and observed experimentally, and this effect was one of the factors explaining the phenomenon of electrical charging of the composite. This electrical potential, when discharged abruptly, can generate an electric spark with sufficient energy for sustained ignition of a solid rocket motor.

ABSTRACT: Experimental investigation was conducted to determine the relative propulsive and combustion behavior of several polyurethane-based solid-fuel formulations containing 30% w/w of paraffin or 10% of aluminum powder. In total, seven solid-fuel formulations were investigated, four containing 30% of paraffin and three with 10% of aluminum. The polyurethane was synthesized with pre-polymer technology. The oxidizer was gaseous oxygen, which was forced into the combustion chamber with axial and swirl methods. Firing tests with 7 configurations were performed. Thrust measurements indicated that the addition of paraffin increased thrust at about 57% and regression rates at about 70%. No relevant improvement in performance was obtained with aluminum addition. Specific impulse decreased when aluminum particles were added to the fuel. The mixture that produced the best ballistic parameters was polyurethane plasticized with castor oil and 30% w/w of paraffin with gaseous oxygen injected through a swirler.

ABSTRACT: The purpose of this article is to present a study on the technological development of propellants, which are used in solid and hybrid rocket motor, that have been employing hydroxyl-terminated polybutadiene (HTPB) as a binder, for the past ten years. The results prove that major research conducted on propulsion technologies continues using HTPB as a binder, with China and the United States being the countries with greater publications, and Brazil appearing at the fifth position in the ranking. The scientific and technological information was collected from articles, conference papers, reviews (over the last ten years) and patents granted in the United States by scientific and USPTO patent databases.

ABSTRACT: Aluminum that is incorporated in an energetic material such as a propellant plays a significant role in the combustion process by means of stabilization with regard to the burning and generation of additional energy. The use of simulation softwares to model the combustion mechanism and kinetic parameters of the elementary reactions that compose the oxidation were used as the pressure variation of the combustion chamber of a rocket motor conditions. The behavior of the molar fraction of the chemical species during the combustion and its posterior stabilization were observed. The systems submitted to higher pressures tend to stabilize more rapidly, according to the greater chemical speed of the elementary reactions.

ABSTRACT: The research for low toxicity and no damage to the environment has stimulated the development of specific investigation lines in many areas. Inevitably, the criteria for safe handling, sensitivity and, above all, specific impulse (efficiencies) of propellant compositions are still superior in relation to ecological appeals. Nowadays, however, the solid or liquid propulsion, as aerospace as military, has already compounds to efficiency and eco-friendly characteristics. This study aimed at describing “green” alternatives to propulsive systems.

The aim of this work was to synthesize a polyurethane polymer matrix using castor oil as a polymer chain modifier, whose characteristics can be adjusted for use as a binder in the manufacture of energetic materials such as propellant and pyrotechnics for aerospace use. We attempted the partial substitution of hydroxyl-terminated polybutadiene (HTPB), a pre-polymer commonly used as a starting polyol in obtaining energetic matrix composites. Thermoanalytical techniques were employed to characterize the material based on castor oil and the unmodified HTPB. The results showed similar behaviors, confirming the possibility of their use as polymer matrix composites through the proposed adaptations.