Aircraft like you've never seen before

Research studies are being conducted for the purpose of building better and more efficient aircraft, using new materials and solutions based on birds.

By Heitor Shimizu, in Michigan  |  Agência FAPESP – In 2015, 3.5 billion passengers traveled by air, this according to the International Air Transport Association (IATA). The number is expected to double by 2034 when Brazil, one of the countries in which the industry has grown most rapidly, is expected to have more than 200 million passengers per year.

“The aviation industry has an enormous impact on the global economy and there is nothing better for rapid travel over long distances than aircraft, which offer a method that is reliable and safe,” said Carlos Cesnik, director of the Active Aeroelasticity and Structures Research Laboratory at the University of Michigan (UM) and professor of Aerospace Engineering.

But, just as it will grow, the industry will go through may changes in the coming years, says Cesnick and the other speakers on a panel that presented alternative technologies for the future of aviation at FAPESP Week Michigan-Ohio, which runs through April 1 in the U.S.

The group led by Professor Daniel Inman of the Aerospace Engineering Department at UM has pursued alternatives for developing more efficient aircraft starting with the study of those who fly most in the world: birds.

According to Inman, the idea for modifying the wings of aircrafts is very old. The Wright brothers themselves used wings that could change shape as they were pulled by cables. “They wanted to learn how to fly and what better way to do that than by using birds as an example,” he said.

However, for reasons of safety – reducing turbulence, for example –, rigid surfaces have dominated aviation from when the industry first became popular up to the present. And it has only been in recent years that interest has again turned to the study of wing configurations that change shape during flight.

“In our study, we do not want to copy how birds flap their wings, but instead, analyze features in the physiology of these creatures that can inspire technological solutions, particularly in applications using intelligent materials,” Inman said.

His group, which includes engineers and experts in animal biology – from UM, Stanford and the University of California Los Angeles –, just this month received a $6 million research grant from the U.S. Air Force Office of Scientific Research to produce the most detailed analysis of bird flight ever conducted in an aeronautical engineering project. “We will be studying the most varied types of birds, in terms of size, shape and speed,” he said.

While today’s aircraft have rigid wings and use parts known as flaps, slats and spoilers for control, birds use their feathers – either singly or combined – to create surfaces that control flight. And there is one other important detail: they do this without wasting energy. That is the main objective of Inman’s research: harness the efficiency of bird flight for use in the aviation industry.

New shapes, new materials

In Brazil, the group led by Edson Cocchieri Botelho, a professor at the School of Engineering of the State University of São Paulo (Unesp) in Guaratinguetá, has studied the use of heat resistant plastic materials in the aviation sector.

Known as composite materials because they have at least two components or two phases, these materials have distinct physical and chemical properties. They are polymeric materials that stand out due to a favorable combination of low specific mass and high mechanical performance.

“Most of the advanced polymeric composites currently in use are obtained from reinforced thermosetting resins that nevertheless present stress problems due to processing and the brittle nature of the resin,” Botelho said.

“Thermoplastic polymers reinforced with continuous fibers are becoming an important replacement when compared with conventional thermosetting polymers because they present higher values of rigidity and impact resistance, higher service temperature and greater versatility in series production,” he said.

In a study funded by FAPESP, Botelho and his team processed thermoplastic composites with different degrees of crystallinity and evaluated the influence of this crystallinity on mechanical and thermal performance involving a variety of environmental conditions.

The project was carried out together with the Aerospace Technical Center (CTA), the Composites Institute of Kaiserslautern and the Leibniz Institute of Polymer Research in Dresden, both of the latter in Germany.

“We have studied structural as well as carbon nanotube reinforced composite materials in joint research studies with groups from the U.S. universities of California, Purdue, Case-Western and Washington,” Botelho told Agência FAPESP.

Much of Brazil’s efforts to develop new technologies aimed at the aviation sector takes place in São José dos Campos as might be expected.

An example was presented during FAPESP Week by João Luiz Filgueiras de Azevedo, coordinator of a research group at the Aeronautics and Space Institute (IAE) of the Department of Aerospace Science and Technology (DCTA), which works primarily with computational fluid dynamics.

The researchers run computer simulations to analyze factors such as velocity, turbulence, pressure, temperature and others that have considerable effect on aircrafts.

The key areas of research are in developing computer and modeling systems and studying factors such as turbulence, aeroacoustics, elasticity, fluid structure interaction, hypersonic flows and aerodynamic optimization.

For more information about FAPESP Week Michigan-Ohio, visit: www.fapesp.br/week2016/michigan-ohio.