The aerospace industry uses carbon fiber reinforced polymer composites to build the structure of rockets, satellites, and jet aircraft. However, such materials tend to be limited in terms of how well they can handle intense heat. But now, a team of researchers from Florida State University’s High-Performance Materials Institute (from FAMU-FSU College of Engineering) is developing a design for a heat shield to help protect the body of these high-speed vehicles. The research has been published in the journal Carbon.
Professor Richard Liang, director of the High-Performance Materials Institute (HPMI), said:
Right now, our flight systems are becoming more and more high-speed, even going into hypersonic systems, which are five times the speed of sound. When you have speeds that high, there’s more heat on a surface. Therefore, we need a much better thermal protection system.
To make the heat shield, the researchers used carbon nanotubes. A carbon nanotube is a cylinder of linked hexagons of carbon atoms, usually ranging from 0.4–40 nanometers in diameter. A sheet of nanotubes is known as “buckpaper” – which is a material with incredible heat and electrical conducting abilities. This sheet, in particular, has been the focus of research at HPMI.
The team discovered that if they soaked the buckpaper in a resin made of a phenol, an aromatic organic compound, the result was a flexible and lightweight material that is also durable enough to potentially protect an object from the intense heat of flying extremely fast.
Heat shields already exist, but they are typically very thick in comparison to the base they protect, explains Ayou Hao, a research faculty member at HPMI. Their new heat shield design differs because it’s thin, sort of like skin rather than heavy armor, that guards the aircraft and aids in supporting its structure from damage at the same time. The fact that it’s so thin means it’s lightweight, and that’s important for engineers who strive to minimize the weight of anything on an aircraft for a better flight.
The team experimented by building heat shields of this new material in a range of thicknesses, then put them all to the test. They applied fire to the samples and monitored how well they prevented heat from reaching the carbon fiber layer beneath. Then, they bent the torched samples to see if the temperature had weakened them in any way.
The results revealed that the buckpaper was better than the control samples at dispersing and keeping heat from reaching the base layer it was protecting. The sheets also remained flexible and strong, more so than the control samples without the protective layer of nanotubes. Flexibility is an instrumental quality, as it means the material is less vulnerable to cracking at extreme temperatures.
The project received third place at the Society for the Advancement of Material and Process Engineering 2019 University Research Symposium and second place among peer-reviewed posters at the 2019 National Space and Missile Materials Symposium.
