Ceramic matrix composites (CMC) are a critical pathway on GE Aviation’s technology roadmap, and recent tests on a GEnx demonstrator engine with GE9X CMC components revealed our bets on this ultra-lightweight, heat-resistant material continue to pay off.

“The GEnx CMC demonstrator engine accumulated 2,800 endurance cycles at a GE’s test cell in Peebles, Ohio and an Avio Aero’s test cell in Naples, Italy,” said Jon Blank, CMC and advanced polymer matrix composite (PMC) design leader. “When we tore down the engine, the CMC parts looked pristine, further confirming the unique characteristics of this material for aerospace use.”

CMCs comprise silicon carbide (SiC) ceramic fibers in a SiC matrix, enhanced by proprietary coatings. For more than 20 years, scientists at GE’s Global Research Centers (GRC) and GE’s industrial businesses worked to develop CMCs for commercial applications.

With one-third the density of metal alloys, lightweight CMC components reduce an engine’s overall weight for improved fuel efficiency. CMC’s high-temperature properties greatly enhance engine performance, durability, and fuel economy. Since CMCs are far more heat resistant than metal alloys, they require less cooling air in the engine’s hot section. This air instead can be used in the engine flow path, enabling it to run more efficiently.

The GE9X engine for the Boeing 777X aircraft will incorporate CMCs in the inner and outer combustor liners, HPT stage 1 shrouds and stage 1 and stage 2 nozzles.

The testing also provided early insight into manufacturing. “The demonstrator testing allows us to perfect our processes before we transition to large-scale production,” stated Blank. “The tests also gave us early data on tolerance limits that will be useful for services and product life cycle.”

Besides CMC components, the GEnx CMC demonstrator engine validated non-CMC parts for the GE9X including the new 3D additive manufactured lightweight low-pressure turbine titanium aluminide (TiAl) blades produced at Avio Aero and the next-generation HPT stage 1 blades with advance cooling technology. The next-generation HPT blades utilize a proprietary process invented at GRC and industrialized at GE Aviation’s Cores & Castings facility in Dayton, OH.  This novel process employs the most efficient cooling circuits ever produced, which result in significant fuel efficiency improvement over historical designs.

CMC testing for the GE9X will continue. The GEnx demonstrator engine will be rebuilt with the same combustor liners, HPT stage 1 shrouds and HPT stage 2 nozzles, LPT TiAl blades and the next-gen HPT blades along with the addition of HPT stage 1 nozzles. A GE9X core with CMC components in the combustor and HPT will begin testing this month.

“This is a generational material technology change,” said Blank. “Everyone in the business is focused on execution. We are most definitely all in on CMCs.”