Advanced Materials Research Vols. 488-489

Abstract: Two series of polymers including polyimides and poly(aryl ether)s were prepared and used as active layers of polymer memories. The poly(aryl ether)-based polymers showed flash behaviors and polyimide-based polymers showed WORM behaviors. The poly(aryl ether)s flash memories can be negatively switched on and positively switched off, and the switching voltages are relative to the chemical structure of bisphenol moiety. On the other hand, the polyimide-based polymer devices can be bidirectionally switched on with comparable positive and negative switching threshold voltages, but cannot be switched off. The polyimides showed write-once-and-read- many-times (WORM) memory behavior. The poly(aryl ether) (AZTA-PAEb) showed very different memory behavior from polyimides (AZTA-PI and AZTA-PEI) although they contain the similar chemical structure (electron-donor triphenylamine and electron-acceptor triazine moieties). The imide structure in the polyimides plays a great role in the memory effects.

Abstract: Aircraft structures are frequently subjected to impacts from objects such as runway debris and birds. In new aircraft structural design, Fiber Metal Laminates (FMLs) play a significant role due to their excellent mechanical properties, particularly the impact properties. In this study, the aircraft sandwich wing with FML face-sheets are analyzed by finite element model for simulating the bird strike. The numerical simulations of bird strike impact are performed adopting a lagrangian approach to design the wing by MSC/PATRAN FE code. The numerical obtained results are compared with the results in the literature for validation of the model. The effect of fiber orientations, fiber types, metal types in FML face sheets in sandwich wing on impact responses are investigated. The impact responses are illustrated by displacement history, contact force history and energy absorption. According to these results, the sandwich panel with FML skin is suitable structure for energy absorption (that is the most important factor in impact phenomena). The lay-ups with titanium metal layer with aramid fibers are the best.

Abstract: TiO₂-AgCl thin films doped with Cu were prepared by sol-gel and coated on glass slide by dip coating process. The prepared thin films were synthesized at the temperature of 400 ^◦C for 2 h with a heating rate of 10^◦C/min. The microstructures of synthesized thin films were characterized by XRD, AFM and SEM. Finally, the light absorption property was evaluated by UV-vis diffuse reflectance spectroscopy. The results show all samples have the thickness in range of 200-250 nm and surfaces are dense with a large surface area. It was found that Cu doping has an effect on light absorption and structure properties of the synthesized thin films. It can be noted that TiO₂-AgCl-5Cu thin films showed the highest light absorption (2.50%) under UV irradiation.

Abstract: By using cryogenic treatment on 7A04 aluminum alloy tested with micrographic analysis and mechanical properties test, we studied the impact on mechanical properties of 7A04 aluminum alloy The results showed that the strength of 7A04 aluminum alloy could be highly increased and the grain size would be reduced in the process through being treated in 480°C/80min + aging in 120°C/4h + cryogenic treatment + aging at 120°C/16h.7A04 aluminum alloy are more fully recrystallized to grain refinement and the tensile strength of it can be increased to 720Mpa after the treatment.

Abstract: SnO₂/N – doped TiO₂ photocatalysts were prepared by the modified sol-gel method. Tin tetrachloride pentahydrate, urea and polyethylene glycol were used as precursors and calcined at a temperature of 500 °C for 2 h for making powders. Different interstitial amount of nitrogen additives were in range of 0 to 40 mol%N. The XRD patterns show the TiO₂ nanocomposites are anatase phase. It was also apparent that doped nitrogen has an effect on crystallite size and band gap energy on absorbed light wavelength leading of enhancement of photocatalytic activity of TiO₂ composite nanoparticles. The result showed 20 mol%N of TiO₂ nanocomposites exhibited high photocatalytic activity, redshift in adsorption edge and a small crystallite size.

Abstract: The influence of temperature, grain size and strain rate on superplasticity of magnesium is investigated. Different approaches are compared along with their experimental results to show the variation in the amount of superplasticity by varying above mentioned parameters. At room temperature magnesium alloys usually have poor formability but recent studies of some alloys such as ZE10, AZ31, AZ61 AZ60, AZ80 and AZ91 are pointing that by varying the temperature along with grain size and strain rate improved formability is possible or even superplastic forming of these alloys can be achieved to meet the demands of automotive, aircraft and other weight conscious industries.

Abstract: In this paper, effects of adding a distributed attached mass added to the face sheets of sandwich panels on free vibration of the system are investigated. Higher order equivalent single layer (ESL) theory is expanded and used. Mass Inertias of the distributed attached mass are taking into account. Various design parameters including geometrical and material properties, such as density, thickness of the attached mass and the panel are investigated to show the decreasing effect on the fundamental natural frequency of the system due to the adding of the distributed attached mass.

Abstract: The objective of this study is to investigate the behavior of Aluminum shells AA5083-H116 under low energy impact and the effects of curvature and thickness were assessed under different impact velocities (5.6, 7.5, 9.5, 11.5 m/s). LS-DYNA software was used to evaluate the amount of absorbed energy by the Aluminum shell during impact under different curvature parameter c. The results showed that the amount of absorbed energy incereases with increasing curvature in a linear relationship which make it possible to predict the amount of absorbed energy for this aluminum alloy under different impact energy. Aslo, the amount of absorbed energy has a direct linear relation with the rise of impact energy. The slopes of curves for absorbed energy with respect to the imapct energy are similar for all curvatures. Shell thickness has inverse effect on the amount of absorbed energy and the relation shows similar ternds with diffrent curvatures. However thick shells show significant increase in maximum force and better stability in the dynamic behavior with less fluctuations in the impact force as the cuvature increases.

Abstract: In this work, polysulfone ultrafiltration membranes were prepared via simple phase inversion with distilled water as non-solvent additive. The main reason for the addition of water in polysulfone dope solution preparation was to enhance the membranes structure. In the dope, 15 wt. % of polysulfone was used and water was varied up to 6 wt. %. The effects of water on morphology, porosity and tensile properties were investigated in detail. From the porosity test, results showed that the addition of water has improved membrane porosity up to 53 %. The FESEM images revealed that membrane morphology has also been modified. However, the tensile properties of membrane decreased as water content increased which may be due to the porosity interaction between polysulfone/NMP with water.