“We paid a lot of attention to ensure that the composite lay down and consolidation are relatively low-temperature processes and that the outgassing, or the products that are released during the assembly process, are in no way harmful,” says Geer. Sustainability concerns also guided Rolls-Royce’s choice of materials for the CFRP components and its design of manufacturing processes that result in minimal waste material.
To manufacture the fan blades, Rolls-Royce builds up hundreds of layers of carbon fiber materials, pre-filled with a resin that increases its toughness. Toray manufactured the carbon fibers, which Hexcel Composites incorporates into the prepreg materials that it supplies. Rolls-Royce partnered with Delaware-based Accudyne to develop the specialized automated robotic systems that perform the material lay-up. The composite components are cured through the application of heat and pressure, and the blades are finished with a thin titanium leading edge to provide protection against erosion, foreign objects and bird strikes. Inspection systems are integrated throughout the process to ensure the quality of each part produced.
The factory’s pre-production technology can be easily scaled up to meet actual production demands, according to Geer. That’s especially important in the aerospace industry, where new aircraft components must go through rigorous qualification testing.
“Once you’ve achieved that certification, you have to be able to prove that the parts that you make subsequently are equivalent to those that were certified. So precision, accuracy and repeatability are a key part of that process,” says Geer. By controlling the manufacturing process, the company is able to demonstrate that the 100th part it builds will be made the same way and to the same quality standards as the first part it built. That’s harder to do when there’s a human factor involved, as in manual lay-up.
The fan blades and cases are not the only composite components on the UltraFan engine. Geer says that organic polymer matrix composites are used extensively throughout the fan system, and other composite materials are incorporated into the acoustic panels, into the infill for aerodynamic fairings and for the annulus (part of the engine combustion system). Ceramic matrix composites are being used in the hot sections of the engine.
Rolls-Royce plans to have the demonstrator model of its UltraFan engine completed by the end of 2021. While the company is in discussions with aerospace manufacturers about including the engines in new aircraft designs, COVID-19-related slowdowns in the industry make it difficult to predict when such projects will move forward.