In 2001, the United States Defense Analysis Institute (IDA) published an evaluation report on the industrial application prospects of ceramic matrix composites (CMCs) for aviation. The conclusion can be summarized in just eight words: the challenge is huge, and the prospect is unknown.
Today, CMC experts from GE Aviation and GE's global R & D centers can laugh at this report. In just two decades, GE has invested hundreds of technical experts and more than 1.5 billion US dollars to focus on CMC technology. Today, CMC technology has become one of the newest and most advanced technologies in the hands of GE, bringing huge changes to the company's own business development and the development of the world aviation industry.
The engine turbine cover produced by GE has been assembled on the best-selling LEAP turbine engine under Safran International (a 50% joint venture between GE and Safran Aero Engines) to provide flight support for hundreds of single-aisle business passenger aircraft.
The advent of CMC components has promoted the promotion of GE products in the military field. GE once produced a prototype engine for the military, setting a new world record for the temperature resistance of jet engines. GE's CMC rotating parts also successfully passed the test.
In 2018, GE Aviation opened its CMC base in Huntsville, Alabama. Counting the three previously established CMC bases, GE has built the first integrated CMC product supply chain in the United States in ten years, which has become an important milestone in the history of CMC technology development. At the same time, GE's new CMC component assembly plant in Asheville, North Carolina has produced more than 40,000 CMC engine turbine covers and has undertaken the production of five CMC high-temperature components for GE9X high-thrust engines.
Ceramic-based composite materials (CMCs) are produced by using silicon carbide, ceramic fibers, and ceramic resins through a complex production process and then painting. Its density and weight are only one-third of the alloy, but its high temperature resistance is much better than the latter, so there is no need to introduce more air into the interior of the high-temperature part and cool it. More air will remain in the airflow channels. Therefore, the engine operates more efficiently under high thrust conditions, with higher energy efficiency, lower emissions, and better durability.
In the history of the development of jet engines, the maximum temperature resistance of turbine engine materials can be increased by about 50 degrees Fahrenheit every ten years. The advent of CMC materials has doubled this number to 150 degrees Fahrenheit. With the increasing popularity of CMC materials in GE engines, the propulsion of the engine is expected to increase by 25%, and the fuel efficiency is expected to increase by 10%.
Although the benefits of using CMC materials are so significant, it is not easy to really realize their industrial application, which has been a problem that has plagued the industry for decades. In addition to the limitations of the molding process, the brittleness of CMC materials has also become its short board. The US government has been funding R & D of CMC materials since the 1970s, and GE scientists have been competing with CMC materials since then. In the 1980s, GE successfully applied CMC to large-scale ground gas turbine engines, and in 1986 applied for the company's first CMC patent. For more than 25 years, GE has successfully applied CMC engine turbine covers to different types of industrial gas turbines.
At the beginning of this century, GE's global R & D center shifted its research and development direction from gas turbine engines to jet turbine engines. Sanjay Correa, who was then in charge of energy and propulsion technology at that time, and later transferred to GE Aviation's CMC program, recalled, "During the development of CMC technology, we began to pay more attention to jet turbine engines. The important characteristics make it have greater development potential in the field of flight. "
At the same time, GE Aviation started to show the results of the application of CMC materials in the engine field to the outside world and set out to build a supply system. As of 2018, GE has established four CMC production bases / R & D centers in Evendale, Ohio, Newark, Delaware, Asheville, North Carolina, and Huntsville, Alabama. Japan Carbon Co., Ltd., as a raw material supplier for CMC, established a joint venture with GE and Safran Group, which played an important role in the preparation of the Huntsville base.
As the latest CMC production site, the Huntsville site covers approximately 100 acres and includes two factories. One is responsible for the production of silicon carbide ceramic fibers with a temperature resistance of up to 2400 degrees Fahrenheit, which is the first high-yield silicon carbide ceramic fiber production line in the United States; the other adjacent factory is responsible for processing silicon carbide ceramic fibers into unidirectional CMC prepreg For subsequent production of CMC parts.
The Huntsville base has been shipping from 2018. At the same time, the demand for CMC materials from GE and Safran engines has increased twenty-fold in ten years, and the growth is unabated. In 2018, the production of CMC materials at the Huntsville base was approximately 6 tons, and this number will increase 10 times in 2028.
With the continuous strengthening of the supply chain, GE Aviation is also continuously improving the production efficiency of CMC products in order to dilute production costs. GE's technological progress in CMC production, casting and coating will greatly promote the latter's application in the field of next-generation engines, which will in turn produce more component products for GE and Safran's civilian / military jet engines.
Jonathan Blank, head of CMC at GE ’s Evendale base laboratory, said that the advancement of digital analysis technology has not only promoted the improvement of jet engine propulsion efficiency, but also profoundly affected the progress of CMC production process.
"We will implement an institutionalized learning model, develop more complete material / process models, and apply digital tools more deeply into the process research and development process, making it an integral part of technology research and development."
The development of CMC materials is highly synchronized with the development of the entire aviation industry. Originally, when the White Brothers built the first human aircraft, wood, steel, and canvas were used as aviation materials. With the continuous upgrading of aircraft, aviation materials have also experienced the development stage of aluminum alloys, titanium alloys and other high-temperature alloys.
Many advanced alloy materials required in the production of jet aircraft were first developed by GE, including single crystal alloys used in the core components of jet engines.
Gary Mercer, vice president of engineering for GE, said: "Basic chemistry and new material processing technologies are the basic guarantee for humans to improve aircraft thermal efficiency, reduce fuel consumption and emissions."
In the 1990s, GE first applied carbon fiber composite materials to engine blades to GE90 turbine engines. Aviation companies are also actively seeking large-scale composite structural components to reduce the weight of the aircraft and improve its durability.
With CMC materials as a weapon, GE can expand its application area from aero engines to a wider aerospace market, and play a role in the latter's harsher space environment.
In this regard, Mercer commented: "What we are experiencing is only the initial stage of the application of CMC materials. In the future development of the aerospace industry, lightweight and high temperature resistance will become hot issues of continuous concern. With the supersonic speed With the advent of supersonic and recyclable spacecraft, CMC will play an increasingly important role in the fields of power systems and aerospace components. "