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%.
Fatigue and damage tolerance issues of GLARE in aircraft structures
Airworthiness regulations require for most structural parts of the aircraft a damage tolerance design philosophy. The fatigue and damage tolerance issues related to the application of the fibre metal laminate Glare in the upper fuselage skin structure are discussed in this paper. As a result of the laminate lay-up (thin aluminium layers with in-between fibre/epoxy layers), the actual stresses in the aluminium layers are higher compared to the applied laminate stresses, resulting in a reduction of crack initiation life compared to monolithic aluminium. However, the crack propagation life is significantly longer than monolithic aluminium due to the bridging by the intact fibres over the fatigue crack. It is discussed that the prediction methods developed for monolithic aluminium can be modified for Glare. Durability issues with respect to moisture absorption and temperature effects are discussed as well as the residual strength of Glare. The through the thickness effects of fatigue in Glare joints are explained and compared to the monolithic aluminium behaviour. Because of the increased fatigue crack propagation life and the higher residual strength of Glare compared to aluminium, higher design allowable stresses are possible, increasing the inspection intervals.
Self-assembly of pyridinium-tailored anthracene amphiphiles into supramolecular hydrogels.
The mixing of a polyacid cross-linker with a pyridinium-functionalized anthracene amphiphile afforded a supramolecular hydrogel through a self-assembly process that was primarily driven by π-stacking and electrostatic interactions.