The University of Sheffield Advanced Manufacturing Research Centre (AMRC) is partnering with 16 industrial partners on the MASTRO project, which is tasked with developing intelligent bulk materials for a smart transport sector as part of Horizon 2020, the biggest EU Research and Innovation program ever with nearly €80 billion of funding available.
“There are three sections within MASTRO: automotive, infrastructure and aerospace; and the AMRC is leading the aerospace section of the project alongside Embraer. We’re developing three main technologies: self-cure, self-anti-icing and self-sensing,” said Matthew Collinson, Research Engineer in the AMRC Composite Centre.
The AMRC team are developing materials through the integration of carbon nanotubes – measured in billionths of a meter – which can be turned into smart products and are now in a position to demonstrate the advances they have made. The development of all three technologies centers on the electrically conductive nature of the composite structure, which is vital as the industry moves to more electrified aircraft, with the ultimate aim of one day being fully electric.
“Firstly, self-curing is a new manufacturing technique for these composites. Currently, they are manufactured in an autoclave but they can be slow and expensive to run. Running electrical current through the fibers of the composite to act as the heating element to cure the component can be cheaper, quicker and uses much less energy. It also complements our work on anti-icing,” said Matthew.
Another disadvantage of using autoclaves to heat composite structures, says Dr Betime Nuhiji, Technical Lead at the AMRC Composite Centre, is that engineers are limited by its size: “An autoclave produces high quality parts but it takes a lot of energy, a lot of time, and you can only create a part that is as big as the autoclave.
“The Boeing 787 is manufactured in the biggest autoclave in the world, but it is expensive, not sustainable and not practical to build these huge autoclaves. The team has developed a heating system where a power supply is directly connected to the composite structure and a current is run through it; so it heats up, just like a heating element.
Matthew said similar technology is used to investigate self-anti-icing: “Currently, aircraft remove surface ice by drawing hot air from the engine to melt the ice, but this takes power away from the engine and is less efficient, so we have been developing an electrical anti-icing system that doesn’t require separate heating elements in the component.
“Linked to both these technologies is self-sensing, monitoring the electrical resistance of the part to detect damage. When you get barely visible impact damage (BVID), the resistance changes so you can monitor that and detect where the damage is. BVID is something the aerospace industry is very interested in because it is very difficult to detect through visual inspection, which they currently do, on composite structures.”
Matthew said to enable these smart functionalities, it has required some development of the resin: “Within a composite, the fibers are extremely electrically conductive but the resin is electrically insulating. Part of the project to develop these bulk materials is to make the component more conductive by mixing carbon nanotubes into the resin, so that the whole part is conductive, not just the fibers. Doing that should enhance every aspect of the MASTRO project. The self-curing and the anti-icing will perform better because the heat is distributed more evenly. And then we will also get increased response in damage detection because, again, the whole composite is conductive rather than just the fibers.”
Betime said the challenge now is creating panels that replicate how they would need to be used in a real-world environment, on the leading-edge of an aeroplane wing, which is two meters long.
The overall objective of the MASTRO project is to develop intelligent bulk materials, incorporating self-responsive properties that increase consumer safety, component lifespan and performance while reducing maintenance and manufacturing costs, and through-life greenhouse gas emissions.