# Ceramic Matrix Composites for Aero Engine Applications--A Review
## 8 The Future of CMCs
### CMC Adoption Roadmap  
Figure 20 presents the engineering challenges that must be addressed to increase the materials' maturity and eventually allow for the adoption in aero-engine applications. The timeframe suggested is based on historical data obtained from the literature review until 2022, and forecasts are based on the reported pace of research. Solutions that can address these requirements can be based on introducing ceramic materials that incorporate a reinforcing phase (whiskers/long fibers) while they are fabricated into a ceramic matrix, allowing for the creation of a CMC material with superior properties. Some of the most common examples are silicon carbide fibers combined with silicon carbide matrix, and aluminum oxide fibers combined in aluminum oxide matrix [236]. Addressing these requirements (Figure 20) will create an understanding of the interaction of the composite constituents with each other and with their application environments. A repetition of composition selection, fabrication, testing, and post-testing will be required to assess their final performance to accomplish these actions. Furthermore, from the table above, a very important priority is the increase in CMC material lifetime. For a few decades, research has focused on progressively increasing the temperature capability, life, and design limit of the available CMCs, but so far, the solution has relied on prioritizing the research focus on fibers, fiber coatings, matrix chemistry, and environmental barrier coatings without focusing on prioritizing on manufacturing facilities for simulation environments and accelerated testing, which might allow the end-users for increased field and experimental testing, which could achieve a more successful result [237; 238; 239]. CMCs development aims to replace monolithic ceramics by achieving better mechanical and thermal properties. This would allow for the creation of more reliable components which can be used with a greater level of confidence, comparable to the confidence offered by metal components [240]. On the other hand, CMCs are in an early development stage, and further research is required before using them in a variety of applications. The growth rate of advanced ceramics and, more specifically, composites was increased worldwide. Focusing on the commercialization of the next-generation ceramic matrix composites for future aerospace applications, water polymers, low-density ceramics, and nanofibers converted to SiC reinforcing fibers for increased toughness are being under  
Figure 19: CMC development process steps. development allowing for better maximum service temperatures [241, 242]. If this outcome is achieved, it is expected from CMCs to grow at a 9.65% rate of value until the year 2026, including oxide/oxide, SiC/SiC, C/C, and C/SiC, according to the international market research results [243]. Figure 21 presents a roadmap for CMC materials, coating, and manufacturing processes for aero-engine applications. Similar to Figure 20, the timeframe suggested is based on historical data obtained from the literature review until 2022, and forecasts are based on the reported pace of research. A critical parameter for high thermal efficiency aero-engines is the high overall pressure ratio that drives high turbine flow path temperatures. The need for developing and applying advanced material technologies, which allow for improved high temperatures, is very high. The introduction of CMC materials in these types of applications allows for a small fuel burn and an additional 50% weight reduction percentage in turbine component weight [244]. Research and development of CMC materials have been ongoing for more than three decades, with aerospace industries, such as GE Aviation and Rolls Royce, investing and applying these materials in process technologies as well as in manufacturing scale-up and supply chain. Some of the most known CMC applications were the construction of shrouds in commercial leap engines used in Boeing, Airbus, and COMAC aircraft engineering.