Synergistic effects of zinc borate and aluminiumtrihydroxide on flammability behaviour of aerospaceepoxy system

The flame retardancy of mono-component epoxy resin (RTM6), widely used for aerospace composites, treated with zinc borate (ZB), aluminium trihydroxide (ATH) and their mixtures at different concentrations have been investigated by morphological and thermal characterization. Cone calorimeter data reveal that combustion behaviour, heat release rate peak (PHRR) and heat release rate average (HRR Average) of RTM6 resin decrease substantially when synergistic effects of zinc borate and aluminium trihydroxide intervene. Thermogravimetric (TGA) results and analysis of the residue show that addition higher than 20% w/w of ZB, ATH, and their mixture greatly promotes RTM6 char formation acting as a barrier layer for the fire development. Depending upon the different used flame additives, SEM micrographs indicate that the morphology of residual char could vary from a compact amalgam-like structure, for the RTM6+ZB system, to a granular structure, characterized by very small particles of degraded resin and additive for the AT

ELECTROCHEMICAL AND MECHANICAL BEHAVIOUR OF TUNGSTEN INERT GAS AND FRICTION STIR WELDING BUTT JOINTS OF AA 2024-T3

Chiesa dell’Annunziata, Ravello (SA), Ital

A comparison between FSW and TIG welding techniques: modifications of microstructure and pitting corrosion resistance in AA 2024-T3 butt joints

An experimental investigation has been carried out, in present paper, on microstructure and corrosion resistance of weld butt joints of AA 2024-T3. Two different welding processes have been considered: a conventional tungsten inert gas (TIG) process and an innovative solid state welding process known as friction stir welding (FSW). Micro-hardness measurements allow pointing out a general decay of mechanical properties of TIG joints, mainly due to high temperatures experienced by material. In FSW joint, instead, lower temperatures involved in process and severe plastic deformations induced by tool motion allow rising of a complex situation: by a general point of view a slight decay of mechanical properties is recorded in nugget zone, flow arm and thermo-mechanically altered zone (TMAZ), while in heat-affected zone (HAZ), due to starting heat treatment of alloy under investigation, a light improvement of such properties is appreciated. In flow arm and in nugget zone, however, a light recovery of hardness, w.r.t. TMAZ zone, is recorded, due to the re-crystallisation of a very fine grain structure. Polarisation curve tests and electrochemical impedance spectroscopy, performed in this paper, allow assessing a generalised nobler behaviour of weld bead with respect to parent alloy. In FSW joint, however, the differences between the three examined zone are not so evident as in TIG joint; what is more, inside FSW weld bead, retreating zone shows a behaviour nobler than advancing one

An Experimental Optimisation of a Spark Ignition Engine Fuel Injector to Reduce the Total Hidrocarbons Emissions During Cold Start Conditions

Engine exhaust emission limits have been subject to increasingly severe controls during the last few years. This has led to the need for a suitably structured systemic approach to the problem of exhaust gas treatment, instead of just focusing on improving catalytic converters efficiency, in other words, it has become increasingly more productive, and necessary, to carry out “global” optimization of the chemical conversion process generally present when gases are burnt, along with activities aimed directly at reduce the cause of their creation, acting on the engine geometric and operating parameters. This work was aimed at an operating experimental analysis of alternative fuel injection systems to optimize their use in order to reduce exhaust emissions in spark ignition engines, especially during cold starts in low temperature conditions

An Overview of the Critical Technological Issues Relevant to the Joining of Light Alloys for Aerospace Applications

Grand Hotel Vesuvio, Sorrento, Ital

An overview of the critical technological issues relevant to the joining of light alloys for aerospace applications

Friction Stir Welding (FSW) is a relatively new technology that was developed at The Welding Institute (TWI) in 1991. It is a solid phase process that operates at temperatures below the melting point of the materials being joined. All aluminium alloys can be welded, including some that cannot be joined by conventional fusion techniques such as Tungsten Inert Gas (TIG). Compared to fusion welding, the relatively low temperatures involved in FSW reduce thermal stresses and distortion. There is substantial potential for employing FSW during the fabrication of various components within the aerospace, shipbuilding, and automotive industries. As these welds may experience diverse aggressive environments, it is crucial to understand the degradation characteristics. This paper looks at some of the key technological issues relevant to the joining of light alloys