At least two technologies will prove critical in tomorrow’s aerospace industry. The first is ceramic-matrix composites technology (CMC or “ceramics”), which feature very high temperature-resistance. The second is additive manufacturing (AM or 3D printing), which provides great flexibility.
How close are we to 3D manufactured CMC components? CMCs are very promising materials in the field of temperature-resistance. They can operate at 1300°C and resist heats up to 260°C higher than nickel-alloys, the most heat-resistant metal alloys, for 1/3 of the weight. And as everyone knows, an engine’s temperature must be increased in order to promote fuel-efficiency. Several engines such as GE aviation’s F-136, which powers the F-35, of CFM’s LEAP engine, which powers both the A320neo and the 737MAX, already have internal CMC components, which help improve its efficiency by “as much as 15%” according to GE. The global ceramic composites market in aircraft engines is growing and could reach $393 million in 2022 according to a July 2017 Forecast by Stratview Research.
Future hypersonic technologies will also require aircraft structures that can resist temperatures caused by great air-friction. Ceramics tiles for example, were already famously used to insulate the Space Shuttle from the heat caused by re-entry.
Additive manufacturing on the other hand, has multiple benefits when used on an industrial scale, including in the aerospace industry. It all comes down to how AM creates shape: by adding successive lairs of material together until the desired volume is reached. Because of this, no precious material is lost in the process (which is inevitable when carving material out of a solid chunk). More importantly, this process allows creating complex single-pieced shapes that cannot be achieved by so-called “subtractive” manufacture, which limits the number of needed fixations. Using AM, GE Aviation was able to merge 855 of its Catalyst engine’s internal components into only 12. Thanks to AM technologies, the lead time for spare parts may also be reduced.
Ahmed Safa, VP of Emirates Engineering, believes that they could soon be reduced from 90 to just 2 days for certain aircraft cabin items, as printing them instantly is quicker than ordering them from a far-away assembly line. Last but not least, thanks to AM, every component can be individually improved at each printing based on feedback from its predecessor, without having to reprogram an entire assembly line!
The Aerospace industry, though cautious by nature, already resorts to additive manufacturing: Boeing for example, has some 50 000 3D-printed components flying on satellites and both military and commercial aircraft. However, 3D-manufactured parts are still mostly non-structural and non-stress-bearing.
AM technologies cannot yet be relied on to create components that are critical to an aircraft’s frame, let alone fabricate complex internal engine parts such as turbine blades. Such components must still be manufactures with more proven methods. But for how long? Will it soon be possible to 3D-manufacture internal engine parts made out of CMCs? This would bring together both AM’s industrial flexibility and CMCs’ resistance proprieties! Several projects are looking into this.
NASA’s “Non-Metallic Turbine Engine Project” for instance, conducted with Honeywell Aerospace, aims to “asses the feasibility of using additive manufacturing technologies to fabricate gas turbine engine components from polymer and ceramic matrix composites”. NASA finds that though AM applied to CMC material isn’t mature enough as of today, “AM and 3D printing of ceramics has the potential to be game changer” in the field of critical aerospace components. The Space Agency has already tested a 3D-manufactured rocket engine in 2015, though it isn’t clear whether or not it contained CMC components. Coming to hypersonics, the Air Force Research Laboratory Aerospace Systems Directorate and California-based HRL Laboratories are currently working together on additive manufacturing for hypersonic flight applications using silicon oxycarbide materials, a family of ceramics, and an advanced AM process whereby a part is formed with pre-ceramic resin before being heated until it is converted to a fully ceramic state. Maybe in a decade from now, it’ll just take 5 minutes to 3D-print a critical turbine blade out of CMCs.
Manufacturers involved in advanced projects being pursued under the Air Force’s Versatile Affordable Advanced Turbine Engines (VAATE) program – such as the Air Dominance Adaptive Propulsion Technology (ADAPT) the Adaptive Versatile Engine Technology (Advent) or the Adaptive Engine Technology Development (AETD) – will surely take a look.
Written by ADIT – The Bulletin and republished with permission.