Recycling of aluminum from fibre metal laminates
Recycling of aluminum alloy scrap obtained from delaminated fibre metal laminates (FMLs) was studied through high temperature refining in the presence of a salt flux. The aluminum alloy scrap contains approximately mass fraction w(Cu) = 4.4%, w(Mg) = 1.1% and w(Mn) = 0.6% (2024 aluminum alloy). The main objective of this research is to obtain a high metal yield, while maintaining its original alloy compositions. The work focuses on the metal yield and quality of recycled Al alloy under different refining conditions. The NaCl-KCl salt system was selected as the major components of flux in the Al alloy recycling. Two different flux compositions were employed at NaCl to KCl mass ratios of 44:56 and 70:30 respectively, based on either the eutectic composition, or the European preference. Different additives were introduced into the NaCl-KCl system to study the effect of flux component on recycling result. Although burning and oxidation loss of the alloying elements during re-melting and refining take place as the drawbacks of conventional refining process, the problems can be solved to a large extent by using an appropriate salt flux. Experimental results indicate that Mg in the alloy gets lost when adding cryolite in the NaCl-KCl salt system, though the metal yield can reach as high as 98%. However, by adding w(MgF2) = 5% into the NaCl-KCl salt system (instead of using cryolite) all alloying elements were well controlled to its original composition with a metal yield of almost 98%.
Recycling of Glass Fibre Reinforced Aluminium Laminates and Silicon Removal from Aerospace Al Alloy
Aerospace aluminium alloys (7xxx and 2xxx series Al alloy) is one of the important Al alloys in our life. The recycling of aerospace Al alloy plays a significant role in sustainable development of Al industry. The fibre reinforced metal laminates GLARE including 67 wt.% 2024 Al alloy was used as upper fuselage in Airbus A380, but the solution for GLARE recycling is not available. Thermal recycling which uses high temperature to decompose the resin and separate the reinforcement fibres and fillers, has been used in the thermal delamination of Lacomet (one member of fibre metal laminates family). Similar to the thermal recycling of Lacomet, a practical solution for GLARE recycling in laboratory-scale was developed in this research.The recycling of GLARE consists of two steps. The first step is the separation of S2-glass fibre and 2024 Al sheets after the decomposition of resins in GLARE under thermal condition, the decomposition behaviour as well as the decomposition kinetics of resins in GLARE were studied. The second step is the re-melting and refining of the separated 2024 Al sheets, the critical influence factors such as the salt flux composition, refining temperature, the size of 2024 Al scrap and the ratio of salt flux to scarp were discussed in this research. Si is a harmful impurity for aerospace Al alloys, and Si concentration is strictly controlled in aerospace Al alloys. But a small amount of Al alloy scrap with high Si concentration is usually mixed together with aerospace Al alloy scrap during the recycling of aerospace Al alloys, thus Si concentration in final secondary aerospace alloys exceeds the upper limit of nominal concentration. Besides the improvement of the efficiency of scrap classification, the removal of impurity Si from recycled aerospace Al alloys is also an option to improve the quality of secondary aerospace Al alloys. In this research, the first attempt on Si removal from Al in laboratory-scale was conducted by using Ti addition method.
The future use of structural composite materials in the automotive industry
The automotive industry's use of structural composite materials began in the 1950s. Since those early days, it has been demonstrated that composites are lightweight, fatigue resistant and easily moulded to shape in other words, a seemingly attractive alternative to metals. However, there has been no widespread switch from metals to composites in the automotive sector. This is because there are a number of technical issues relating to the use of composite materials that still need to be resolved including accurate material characterisation, manufacturing and joining. This paper reports the findings of a recent European initiative that examined the future use of composite materials in the automotive sector. The principal technical challenges that must be overcome in ten key areas relating to composite usage are reviewed. Furthermore, recommendations for future research priorities to overcome these challenges are presented.