3D woven near-net-shape preforms for CMC airfoils

Ceramics and ceramic matrix composites (CMCs) had emerged as promising materials for solar thermal receivers due to their unique properties, including excellent thermal stability, high thermal conductivity, high corrosion resistance, and superior mechanical properties, all of which enhanced the performance and durability of solar thermal receivers. Additionally, their lightweight nature, achieved through the use of ceramic matrix composites, optimized overall system performance. Various types of ceramics and ceramic matrix composites had been assessed for their applicability in solar thermal receivers, such as alumina, zirconia, mullite, silicon carbide, silicon nitride, and ultrahigh temperature ceramics (UHTCs). Consequently, advanced ceramic matrix composites, novel coating technologies, and innovative manufacturing techniques were explored to further optimize the efficiency and reliability of solar thermal receivers. Innovative ceramic matrix composites, such as alumina/silicon carbide and silicon carbide/silicon carbide (SiC/SiC), were examined for their superior mechanical strength and thermal conductivity. Moreover, the utilization of a novel class of fiber-reinforced ultra-high temperature ceramic matrix composites, which featured improved optical properties, high mechanical strength at elevated temperatures, thermal shock resistance, and lightweight characteristics, created opportunities for advancing solar thermal receiver design and optimizing performance as solar absorber materials.

The electrophysical properties of ceramic–crystal matrix composites are studied. Piezoelectrically active PZT/LiNbO3 ceramic matrix composites with LiNbO3 concentrations of 0–20 vol % are fabricated. Complex elastic, dielectric, and piezoelectric parameters are measured, and the microstructural characteristics of the obtained samples are studied experimentally. It is found that the extreme electrophysical properties of ceramic–crystal matrix composites depend on the properties and structure of the piezoceramic matrix and crystalline filler, and on the matrix microporosity produced during sintering. The electrophysical parameters of ceramic–crystal matrix composites as functions of crystalline filler content are established through the competing microporosity growth effects of the ceramic matrix and the increase in crystalline filler content.

A high-temperature, high-pressure, tube furnace has been used to evaluate the long term stability of different monolithic ceramic and ceramic matrix composite materials in a simulated combustor environment. All of the tests have been run at 150 psia, 1204°C, and 15 percent steam in incremental 500 h runs. The major advantage of this system is the high sample throughput; >20 samples can be exposed in each tube at the same time under similar exposure conditions. Microstructural evaluations of the samples were conducted after each 500 h exposure to characterize the extent of surface damage, to calculate surface recession rates, and to determine degradation mechanisms for the different materials. The validity of this exposure rig for simulating real combustor environments was established by comparing materials exposed in the test rig and combustor liner materials exposed for similar times in an actual gas turbine combustor under commercial operating conditions. [S0742-4795(00)02402-9]

A high-temperature, high-pressure, tube furnace has been used to evaluate the long term stability of different monolithic ceramic and ceramic matrix composite materials in a simulated combustor environment. All of the tests have been run at 150 psia, 1204°C, and 15% steam in incremental 500 h runs. The major advantage of this system is the high sample throughput; >20 samples can be exposed in each tube at the same time under similar exposure conditions. Microstructural evaluations of the samples were conducted after each 500 h exposure to characterize the extent of surface damage, to calculate surface recession rates, and to determine degradation mechanisms for the different materials. The validity of this exposure rig for simulating real combustor environments was established by comparing materials exposed in the test rig and combustor liner materials exposed for similar times in an actual gas turbine combustor under commercial operating conditions.

There are significant challenges for materials in extreme environments for a variety of applications such as aircraft engines, gas turbines, nuclear reactors, reentry vehicles, and hypersonic structures. Ceramic matrix composites (CMCs) could be ideal candidates to meet these stringent requirements for materials due to their high melting temperatures, high oxidation, corrosion and ablation resistance, low creep, and thermal cycling behavior in such extreme environments. Particularly, continuous fibers can bridge cracks in CMCs and therefore improve the strength and fracture toughness of composites. CMCs are traditionally manufactured by the melting infiltration method. With this method, the high porosity and brittle structure of fabricated CMCs are not capable of withstanding high mechanical and thermal loads. Alternatively, polymer derived ceramic composites are fabricated by incorporating carbon fibers into polymer derived ceramic matrix to achieve high fracture toughness. With the aid of protective coatings with metallic or ceramic materials, such as Nickel and boride nitride, carbon fiber could potentially withstand high temperatures without oxidation. In this study, continuous fiber reinforced silicon oxycarbide composite was manufactured with polysiloxane (PSX) resin and woven carbon fabrics through the polymer infiltration and pyrolysis process (PIP). Re-infiltration of the PSX resin into the composites, curing in an autoclave, and pyrolysis for additional 2 to 10 cycles can increase the yield of ceramics of the composites. A dense structure of the composites was observed by SEM. The EDS results showed that the elemental composition of the composites mainly consisted of carbon, silicon and oxygen. The crystalline structure of the composites was examined through XRD to indicate the degree of polymer pyrolysis to ceramics. The results of four-point bending testing of the composites showed a flexural strength of 62.17MPa, a flexural modulus of 51.30GPa, and a fracture toughness of 1.3 × 108J/m3.

Amorphous Si-B-C-N ceramic fibers prepared at 1000°C from a melt-processable boronmodified polysilazane [B(C2H4SiCH3NCH3)3]n were annealed in the temperature range 1000-1800°C in a nitrogen atmosphere to identify the changes in the thermal and structural stability as well as in the related fiber strength. Fibers were shown to be extremely stable up to 1600°C without decomposition and measurable changes in their amorphous structure. At higher temperatures, X-ray diffraction and thermogravimetry analyses indicated that the structural and thermal properties of fibers were probably controlled by the carbothermal decomposition of a minor part of the silicon nitride phase providing SiaNVSiC nanograins in the material at high temperature. The excellent strength retention after heat-treatment at 1600°C (1.3 GPa) is clearly related to the high structural and thermal stability of fibers. Between 1600°C and 1700°C, the fiber strength decreased to 0.9 GPa then dropped to about one-quarter the original value at 1800°C while structural changes were evident. With an excellent stability in air at 1300°C, these Si-B-C-N fibers are potential candidates for Continuous Fiber-reinforced Ceramic-matrix Composites (CFCCs). INTRODUCTION There is long interest and demand of aerospace industry for ceramic matrix composites because of their superior properties compared to monolithic ceramic materials. In a general way, such lightweight structural materials are made from a variety of continuous fibers and matrix combinations in which fibers, embedded in the ceramic matrix, act as the reinforcing phase in Continuous-reinforced Ceramic matrix Composites (CFCCs). Performances of CFCCs for hightemperature aerospace and energy-related areas depend upon judicious selection of fibers with the proper chemical and physical properties of the ceramic which is employed. Non-oxide ceramic fibers are particularly attractive for their light weight, thermal shock resistance, creep resistance and relatively high tensile strength and modulus values making them useful for aerospace applications. Among them, those fibers prepared from organometallic/inorganic polymers are of particular interest because of their small diameter and flexibility to allow weaving To the extent authorized under the laws of the United States of America, all copyright interests in this publication are the property of The American Ceramic Society. Any duplication, reproduction, or republication of this publication or any part thereof, without the express written consent of The American Ceramic Society or fee paid to the Copyright Clearance Center, is prohibited.

Composite materials are engineered materials made from two or more constituent materials. They have significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure. The advantage of composite material is that they exhibit the best qualities of their components or constituents and often some qualities that neither constituent possesses. The properties that can be improved by forming a composite material are strength, stiffness, corrosion resistance, wear resistance, weight, thermal insulation, thermal conductivity, etc. Composite materials can be classified and characterized into four commonly accepted types; (1) fibrous composite materials that consist of fibers in a matrix, (2) laminated composite materials that consist of layers of various materials, (3) particulate composite materials that are composed of particles in a matrix and (4) the combination of some or all the first three types (Jones, 1999). According to the matrix phase the composites are divided into three groups; (1) metal matrix composites (MMCs), (2) polymer matrix composites (PMCs) and (3) ceramic matrix composites (CMCs). Ceramic materials in general have very attractive properties e.g.: high strength and high stiffness at very high temperatures, chemical inertness and low density. In the presence of flaws (surface or internal) they are prone to catastrophic failures. Ceramic materials can be toughened by incorporating fibers and thus exploit the attractive high-temperature strength and environmental resistance of ceramic materials without risking a catastrophic failure (Chawla, 1987). According to the basics written above, a monolithic silicone carbide (SiC) was used as a matrix phase, which has been recognized as one of the most promising structural materials for many thermo-mechanical applications because of its excellent hightemperature strength and modulus, good oxidation resistance, high hardness, low specific weight and low density (Xin-Bo & Hui, 2005; Xin-Bo et al., 2000; She et al., 1999). The problem with monolithic SiC is its low thermal shock resistance, which leads to cracking and catastrophic failure of the material. Thermal shock resistance and crack propagation can 6

Ceramic materials are well suited for tribological applications due to their superior hardness, high wear resistance, good chemical resistance, stability at high temperatures, etc. Ceramic pairs are commonly used in extreme environmental applications, such as high loads, high speeds, high temperatures and corrosive environments. This present chapter briefly discusses the friction and wear behaviour of ceramics and ceramic matrix composites. Friction of ceramics depends largely on fracture toughness besides normal load, sliding speed, temperature, etc. Wear mechanisms in ceramics involve fracture, tribo-chemical effects and plastic flow. In case of ceramic matrix composites, the incorporation of the secondary phase into ceramic matrix results in the improvement of both mechanical properties and friction performance. In nano-ceramics, reduction in microstructural scale yields significant improvements in wear resistance. Tribological behaviour of ceramics in biological environment is also highlighted.

Advances in Ceramic Matrix Composites

General Overview and Applications of Ceramic Matrix Composites (CMCs)

Graphene nanoplatelets (GNPs) are considered to be one of the most promising new reinforcements due to their unique two‐dimensional structure and remarkable mechanical properties. In addition, their impressive electrical and thermal properties make them attractive fillers for producing multifunctional ceramics with a wide range of applications. This paper reviews the current status of the research and development of graphene‐reinforced ceramic matrix composite (CMC) materials. Firstly, we focused on the processing methods for effective dispersion of GNPs throughout ceramic matrices and the reduction of the porosity of CMC products. Then, the microstructure and mechanical properties are provided, together with an emphasis on the possible toughening mechanisms that may operate. Additionally, the unique functional properties endowed by GNPs, such as enhanced electrical/thermal conductivity, are discussed, with a comprehensive comparison in different ceramic matrices as oxide and non‐oxide composites. Finally, the prospects and problems needed to be solved in GNPs‐reinforced CMCs are discussed.

Towards physical properties tailoring of carbon nanotubes-reinforced ceramic matrix composites

Multiscale ceramic matrix composite thermomechanical damage model with fracture mechanics and internal state variables

As part of an ongoing research development at Carleton University in ceramic matrix composites (CMCs) for high-temperature gas turbine applications, it was recognized that the performance of an oxide matrix could be improved by incorporating a metal reinforcement material. For this reason, a low cost CMC was created by reinforcing a yttria-stabilized zirconia (7YSZ) ceramic matrix with a Hastelloy X (HX) wire mesh. The CMC was manufactured by coating the HX mesh with a NiCrAlY bond coat, and then 7YSZ ceramic matrix, both using plasma spraying. The bond coat was employed to improve bonding and also to act as an oxygen diffusion barrier. In order to evaluate the performance of the HX/7YSZ composite at high temperatures, isothermal and cyclic oxidation tests were carried out for 1000 hours at 1050°C. The results showed that oxidation resistance was improved by vacuum heat treatment prior to testing due to the formation of stable thermally grown oxides (TGO) on the NiCrAlY bond coat. In the cyclic oxidation test, differences in thermal expansion coefficients caused cracking at interfaces between mesh/bond coat and bond coat/7YSZ. Minimizing the effect of thermal expansion by better material combination, as well as modifying manufacturing methods will allow for improved performance of metal mesh reinforced CMCs.

Ceramic matrix materials have attracted great attention from researchers and industry due to their material properties. When used in engineering systems, and especially in aero-engine applications, they can result in reduced weight, higher temperature capability, and/or reduced cooling needs, each of which increases efficiency. This is where high-temperature ceramics have made considerable progress, and ceramic matrix composites (CMCs) are in the foreground. CMCs are classified into non-oxide and oxide-based ones. Both families have material types that have a high potential for use in high-temperature propulsion applications. The oxide materials discussed will focus on alumina and aluminosilicate/mullite base material families, whereas for non-oxides, carbon, silicon carbide, titanium carbide, and tungsten carbide CMC material families will be discussed and analyzed. Typical oxide-based ones are composed of an oxide fiber and oxide matrix (Ox-Ox). Some of the most common oxide subcategories are alumina, beryllia, ceria, and zirconia ceramics. On the other hand, the largest number of non-oxides are technical ceramics that are classified as inorganic, non-metallic materials. The most well-known non-oxide subcategories are carbides, borides, nitrides, and silicides. These matrix composites are used, for example, in combustion liners of gas turbine engines and exhaust nozzles. Until now, a thorough study on the available oxide and non-oxide-based CMCs for such applications has not been presented. This paper will focus on assessing a literature survey of the available oxide and non-oxide ceramic matrix composite materials in terms of mechanical and thermal properties, as well as the classification and fabrication methods of those CMCs. The available manufacturing and fabrication processes are reviewed and compared. Finally, the paper presents a research and development roadmap for increasing the maturity of these materials allowing for the wider adoption of aero-engine applications.