ABSTRACT: The present study assesses the influence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950 °C and 1050 °C in a furnace with controlled atmosphere of argon + 10% H2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes's method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated significant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.

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.

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.