Enhanced resistance to atomic oxygen of OG POSS/epoxy nanocomposites

Atomic oxygen (AO) in the low Earth orbit (LEO) space is critical to polymer matrix composites. AO strikes the surfaces of materials with sufficient energy to break chemical bonds. In this study, to solve the problem of undercutting of polymer matrix composite by AO, an octaglycidyldimethylsilyl (OG) polyhedral oligomeric silsesquioxane (POSS)/epoxy nanocomposite was proposed to improve the resistance of epoxy to AO. OG POSS/epoxy nanocomposites were fabricated and AO exposure test was carried out to confirm the improvement of resistance to AO. Consequently, it was observed that OG POSS increased the resistance of epoxy to AO. Compared with neat epoxy, OG POSS/epoxy nanocomposite containing 10 wt% OG POSS exhibited a reduction of 67% in mass loss by AO. OG POSS could be readily adapted to epoxy without a complex homogenization process. Therefore, this technology will be an effective way to help epoxy matrix composites survive in severe LEO space environments.N

Nano filled polybenzimidazole (PBI) film coating for improved environmental performance in space

The spacecraft in the low earth orbit (LEO) is influenced by many parameters like Atomic oxygen, High Vacuum, thermal cycling, Ultraviolet radiation and MMOD impacts. It is essential to study the response of the material in these conditions because they have a degradatory effect on the material. This paper discusses about an approach to improve the structural performance of the composite structure (CFRP) for space applications using carbon nanotube (CNT) as a filler in a Polybenzimidazole (PBI) film coated on the composite structure. A 2 wt% CNT/PBI film was coated mechanically and cured in a vacuum oven. The PBI/CFRP and the CNT-PBI/CFRP coated samples were studied for LEO environment test for effective radiation shielding and hypervelocity impact test for energy absorption. The use of CNTs in the PBI coating improved the shielding performance in LEO by 35.21%. SEM analysis also showed that the surface cracks decreases with the introduction of CNTs. However, there was no significant improvement noticed in the hypervelocity impact tests for a similar value of film thickness.N

Hypervelocity impact on flexible curable composites and pure fabric layer bumpers for inflatable space structures

Demands for large space structures recently increased in accordance with the growth of space applications for micro-gravity research and space travel. To satisfy growing demand, inflatable structures have been developed. For hypervelocity impact protection from micrometeoroid and orbital debris with enough structural flexibility to be applied to an inflatable space structure, a Multi-shock shield was developed and adopted. However, the multi-layered ceramic fabric bumper of the Multi-shock shield is inferior to the bumper of the conventional stuffed Whipple shield with respect to its hypervelocity impact protection performance. In this study, the applicability of directly curable carbon, Zylon and Twaron composites as a front bumper of the hypervelocity impact shield was examined through 22 experiments involving a pure fabric layer bumper. Through the experiments, it was found that directly curable composites can be more effectively used as a bumper of hypervelocity shield than pure fabric layers. (C) 2017 Elsevier Ltd. All rights reserved.N

Visible-Light-Induced Arylthiofluoroalkylations of Unactivated Heteroaromatics and Alkenes

Visible-light-induced arylthiofluoroalkylations of unactivated heteroaromatics and alkenes have been developed utilizing readily available arylthiofluoroalkyl sources. This method enables simultaneous installation of sulfur and fluoroalkyl moieties, two important functional groups, which demonstrates its potential use for late-stage modifications in the synthesis of functional molecules. This method can be easily utilized to fine-tune the properties of lead molecules in drug development by controlling the number of fluorine atoms in the reagents

Recent research trends in textile-based temperature sensors: a mini review

In this review, the current state of research on textile-based temperature sensors is explored by focusing on their potential use in various applications. The textile-based sensors show various advantages including flexibility, conformability and seamlessness for the wearer. Integration of the textile-based sensors into clothes or fabric-based products enables continuous and sensitive monitoring of change in temperature, which can be used for various medical and fitness applications. However, there are lacks of comprehensive review on the textile-based temperature sensors. This review introduces various types of textile-based temperature sensors, including resistive, thermoelectric and fibre-optical sensors. In addition, the challenges that need to be addressed to fully realise their potential, which include improving sensitivity and accuracy, integrating wireless communication capabilities, and developing low-cost fabrication techniques. The technological advances in textile-based temperature sensors to overcome the limitations will revolutionize wearable devices requiring function of temperature monitoring

Polybenzimidazole (PBI) film coating for improved hypervelocity impact energy absorption for space applications

This paper deals with how the use of Polybenzimidazole (PBI) as a film coating over conventional composite designs could help improve the hypervelocity impact ballistic performance of the system. PBI coated composite samples were studied for resistance to Low Earth Orbit environment conditions like high vacuum, thermal cycling, Atomic Oxygen and Ultraviolet Radiation in a simulation facility. It was observed that the PBI coated composites reduced mass loss and surface erosion compared to the non-coated samples after LEO exposure. Hypervelocity impact experiments were conducted on the PBI coated composites for impact velocities between 2.5 to 3 km/s. The experiments showed that the PBI film coating significantly increased the energy absorption of the composite system. The effect of thickness increase as a result of the film application on energy absorption was also found to be negligible confirming the effectiveness of PBI coating as a hypervelocity shield.N