Emissions of future conventional aircrafts adopting evolutionary technologies.

The current aviation sector has been shaken by COVID-19, but a few years prior, the industry was experiencing a time of prosperity never seen before. These years were marked by the introduction of new models and record sales. In particular, two cases stood out from the rest: the Boeing 737 MAX and the Airbus A320neo. Such overwhelming success in sales was partly because in essence, these are quite traditional and familiar aircrafts that featured improvements in some critical systems, notably in the use of newer engines. Current projections suggest that the pre-COVID growth rate of aviation will resume in a few years, which raises global concerns regarding the ecological burden of conventional aircraft and their resulting limitations. By reviewing the green technologies likely to be incorporated into conventional aviation over the next 30 years, we explore the limits of the industry's current approach. To this end, we reconstruct an already validated life cycle analysis model to assess a fleet of aircraft and analyze the impacts of these new technologies on emissions. Based on data from the literature, predictions are made for optimistic and pessimistic scenarios in a post-COVID world. The results are compared with the globally established targets set by the International Air Transport Association (IATA). Simulations show that a future based solely on conventional aircrafts using evolutionary technologies is of great concern. There is a need to promote a radical departure from the current aviation models to accommodate the growing demand for aviation with a green future.

Damage Characterization of Bio and Green Polyethylene-Birch Composites under Creep and Cyclic Testing with Multivariable Acoustic Emissions.

Despite the knowledge gained in recent years regarding the use of acoustic emissions (AEs) in ecologically friendly, natural fiber-reinforced composites (including certain composites with bio-sourced matrices), there is still a knowledge gap in the understanding of the difference in damage behavior between green and biocomposites. Thus, this article investigates the behavior of two comparable green and biocomposites with tests that better reflect real-life applications, i.e., load-unloading and creep testing, to determine the evolution of the damage process. Comparing the mechanical results with the AE, it can be concluded that the addition of a coupling agent (CA) markedly reduced the ratio of AE damage to mechanical damage. CA had an extremely beneficial effect on green composites because the Kaiser effect was dominant during cyclic testing. During the creep tests, the use of a CA also avoided the transition to new damaging phases in both composites. The long-term applications of PE green material must be chosen carefully because bio and green composites with similar properties exhibited different damage processes in tests such as cycling and creep that could not be previously understood using only monotonic testing.