Continuous Fiber-reinforced Ceramic Composites Research Articles

Fabrication of bamboo-inspired continuous carbon fiber-reinforced SiC composites via dual-material thermally assisted extrusion-based 3D printing

Ceramic matrix composites (CMCs) structural components encounter the dual challenges of severe mechanical conditions and complex electromagnetic environments due to the increasing demand for stealth technology in aerospace field. To address various functional requirements, this study integrates a biomimetic strategy inspired by gradient bamboo vascular bundles with a novel dual-material 3D printing approach. Three distinct bamboo-inspired structural configurations Cf/SiC composites are designed and manufactured, and the effects of these different structural configurations on the CVI process are analyzed. Nanoindentation method is utilized to characterize the relationship between interface bonding strength and mechanical properties. The results reveal that the maximum flexural strength and fracture toughness reach 108.6 ± 5.2 MPa and 16.45±1.52 MPa m1/2, respectively, attributed to the enhanced crack propagation resistance and path caused by the weak fiber-matrix interface. Furthermore, the bio-inspired configuration enhances the dielectric loss and conductivity loss, exhibiting a minimum reflection loss of −24.3 dB with the effective absorption band of 3.89 GHz. This work introduces an innovative biomimetic strategy and 3D printing method for continuous fiber-reinforced ceramic composites, expanding the application of 3D printing technology in the field of CMCs.

Computational study of micromechanical damage behavior in continuous fiber-reinforced ceramic composites

A comprehensive numerical analysis of micromechanical damage behavior in a continuous fiber-reinforced ceramic composite is presented. A three-dimensional micromechanical finite element modeling procedure is developed for effective elastic property estimation and damage evaluation by the example of a composite consisting of a silicon carbide matrix unidirectionally reinforced with silicon carbide fiber (SiC/SiCf). The effect of a fiber/matrix interface on predicted elastic properties of the SiC/SiCf composite is considered. Representative volume element (RVE) models are developed for an SiC/SiCf composite with damageable interfaces. Statistically equivalent RVE models with randomly distributed fibers are generated using a developed algorithm. The statistical variability of fiber and matrix strengths is considered in developing RVE models and assumed to follow a Weibull probability law. A user-material subroutine with an adaptive material constitutive law is developed to predict damage behavior in the RVE. The predicted uniaxial stress versus strain behavior and damage in the composite are discussed.

Materials Characterization in Continuous Fiber-Reinforced Ceramic Composites Served in Simulating Environment

Materials characterization is a crucial issue in the development and application of new materials. Materials characterization aims to mine and acquire characteristic information and their evolution in the materials. It mainly includes three important topics which are microstructural characterization, properties characterization, and environmental degradation. In this paper, characterization techniques about these topics were discussed for C/SiC composites and a characterization system was preliminarily established. All these characterization research and their results further the better understanding of the relationship between microstructure and properties and of the failure mechanisms in the C/SiC composites.

Status and Prospects of SiC-Based Ceramic Composites for Fusion and Advanced Fission Applications

The present status and future prospects of silicon carbide (SiC) continuous fiber-reinforced SiC-matrix ceramic composites (SiC⁄SiC composites) is reviewed from the viewpoint of material development for applications to blanket ⁄ first wall structures in fusion power devices and other advanced nuclear systems. Emphases are placed on the directions of neutron-tolerant composite development. A rationalization of thermal conductivity limits for SiC⁄SiC composites is provided. It is concluded that, although today’s state-of-the-art SiC⁄SiC can contribute to ‘attractive’ fusion power, the expected emergence of novel composites shall further justify taking the risk of employing untraditional materials.

Modeling the Thermostructural Capability of Continuous Fiber-Reinforced Ceramic Composites

There exists today considerable interest in developing continuous fiber-reinforced ceramic matrix composites (CMC) that can operate as hot-section components in advanced gas turbine engines. The objective of this paper is to present simple analytical and empirical models for predicting the effects of time and temperature on CMC tensile rupture under various composite and engine conditions. These models are based on the average rupture behavior measured in air for oxide and SiC-based fibers of current technical interest. For example, assuming a cracked matrix and Larson-Miller rupture curves for single fibers, it is shown that model predictions agree quite well with high-temperature stress-rupture data for SiC/SiC CMC. Rupture models, yet to be validated, are also presented for three other relevant conditions: (a) SiC fibers become oxidatively bonded to each other in a cracked CMC, (b) applied CMC stresses are low enough to avoid matrix cracking, and (c) Si-based CMC are subjected to surface recession in high-temperature combustion gases. The practical implications of the modeling results are discussed, particularly in regard to the optimum fibers and matrices for CMC engine applications and the thermostructural capability of SiC/SiC CMC in comparison to nickel-based superalloys, monolithic ceramics, and oxide/oxide CMC.

Evaluation of CFCC liners with EBC after field testing in a gas turbine

Under the Ceramic Stationary Gas Turbine (CSGT) Program sponsored by the U.S. Department of Energy (DOE), a team led by Solar Turbines Incorporated has successfully designed engines, utilizing silicon carbide/silicon carbide (SiC/SiC) continuous fiber-reinforced ceramic composite (CFCC) combustor liners. Their potential for low NO x and CO emissions was demonstrated in eight field-engine tests for a total duration of more than 35,000 h. In the first four field tests, the durability of the liners was limited primarily by the long-term stability of SiC in the high steam environment of the gas turbine combustor. Consequently, the need for an environmental barrier coating (EBC) to meet the 30,000-h life goal was recognized. An EBC developed under the National Aeronautics and Space Administration high speed civil transport, enabling propulsion materials program was improved and optimized under the CSGT program and applied on the SiC/SiC liners by United Technologies Research Center (UTRC) from the fifth field test onwards. The evaluation of the EBC on SiC/SiC liners after the fifth field test with 13,937-h at Texaco, Bakersfield, CA, USA is presented in this paper.

Abrasive Water Jet Machining Mechanisms in Continuous-Fiber Ceramic Composites

Advanced continuous fiber-reinforced ceramic composite (CFCC) materials have been machined with abrasive water jet (AWJ) drilling and cutting processes. Cutting forces, surface microstructure, and retained tensile behaviors were evaluated using dynamometry, surface profilometry, scanning electron microscopy, and tensile testing, respectively. The AWJ surface characteristics, i.e., roughness and the micromechanisms of material removal of CFCCs, were compared with those of a conventional diamond saw cut surface. Material removal mechanisms for AWJ cutting of CFCC consist of a combination of bending, shearing, micromachining, and erosion. The micromechanisms associated with AWJ hole drilling, or piercing on the other hand, are microfracture of fibers and matrix, delamination, and fragmentation of fiber bundles. The tensile mechanical behavior is negligibly different between the AWJ machined and diamond grit ground CFCC materials.

Monazite-containing oxide/oxide composites

An extremely simple processing route has been used to produce LaPO 4 (La-monazite)/alumina continuous fiber-reinforced ceramic composites. In this paper, the processing, microstructure and tensile properties are reviewed. In particular, the damage tolerance and notch insensitivity of this system, which contains monazite-coated fibers, will be compared to the properties reported for other oxide composites.

SiC/SiC複合材料研究・開発の現状と今後の展望

SiC fiber-reinforced SiC matrix composites (SiC/SiC composites) are attractive structural materials for next-generation high-temperature applications, because the density of such a composite is only one third of the conventional heat-resistance one, and it has superior oxidation resistance due to the formation of SiO2 on the surface in the air at elevated temperatures. A research and development activity to realize high efficiency gas turbine materials and aerospace materials replaced C/C composites has been initiated. Continuous fiber-reinforced ceramic composites (CFCC), including SiC/SiC composites, should be showed to prevent crack propagation due to deflection and scattering of micro cracks initiated in the matrix around the interphase. As the crack-opening displacement (COD) is increased, the reinforced fibers should bridge the matrix and they will break after pull out. The apparent fracture resistance can be increased. As a result of this sequence of phenomena, the CFCC shows the better mechanical properties than that of the monolithic ceramics. Therefore, interpretation of the fracture mechanism at the interface between the fibers and the matrix is essential to improve mechanical properties. Currently, many efforts are being made to develop the advanced SiC/SiC composites from “state-of-the-art” materials by a number of research organizations, including universities, national institutes and industries in the world. In this paper, the current status of research and development of SiC/SiC composites is described together with our results of microstructure analysis using advanced microscopy, and future prospects are also discussed.

Ceramic Stationary Gas Turbine Development Program—Fifth Annual Summary

A program is being performed under the sponsorship of the United States Department of Energy, Office of Industrial Technologies, to improve the performance of stationary gas turbines in cogeneration through the selective replacement of metallic hot section components with ceramic parts. The program focuses on design, fabrication, and testing of ceramic components, generating a materials properties data base, and applying life prediction and nondestructive evaluation (NDE). The development program is being performed by a team led by Solar Turbines Incorporated, and which includes suppliers of ceramic components, U.S. research laboratories, and an industrial cogeneration end user. The Solar Centaur 50S engine was selected for the development program. The program goals included an increase in the turbine rotor inlet temperature (TRIT) from 1010°C (1850°F) to 1121°C (2050°F), accompanied by increases in thermal efficiency and output power. The performance improvements are attributable to the increase in TRIT and the reduction in cooling air requirements for the ceramic parts. The ceramic liners are also expected to lower the emissions of NOx and CO. Under the program uncooled ceramic blades and nozzles have been inserted for currently cooled metal components in the first stage of the gas producer turbine. The louvre-cooled metal combustor liners have been replaced with uncooled continuous-fiber reinforced ceramic composite (CFCC) liners. Modifications have been made to the engine hot section to accommodate the ceramic parts. To date, all first generation designs have been completed. Ceramic components have been fabricated, and are being tested in rigs and in the Centaur 50S engine. Field testing at an industrial co-generation site was started in May, 1997. This paper will provide an update of the development work and details of engine testing of ceramic components under the program.

Development of test standards for continuous fiber ceramic composites in the United States

Standardization activities in the United States for continuous fiber-reinforced ceramic composites (CFCCs) are reviewed. This brief review focuses on the development of test standards by subcommittee C28.07 of the American Society for Testing and Materials (ASTM) on the drafting of a section of a design code for ceramic and ceramic matrix composite components as part of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, and on the development of a set of volumes on ceramic matrix composites for Military Handbook 17 on composites. The participation of the US in the international harmonization of standards for CFCCs is also reviewed.

Analysis of oxidation-assisted stress-rupture of continuous fiber-reinforced ceramic matrix composites at intermediate temperatures

Abstract A model is presented to estimate the reliability and time-to-failure of an unidirectional continuous fiber-reinforced ceramic composite when subjected to stresses beyond the matrix cracking stress. The particular case of oxidation-assisted stress-rupture at intermediate temperatures is considered. The effects of stress and temperature on the reliability of the model composite are examined. Model predictions are presented for the specific case of CG-Nicalon™/SiC CFCCs with carbonaceous fiber coatings.

The role of interfacial coatings on the high frequency fatigue behavior of nicalon/C/SiC composites

A significant number of researchers have shown that, under monotonic loading, a weak fiber/matrix interface is desirable in obtaining toughness and graceful failure in continuous fiber reinforced ceramic composites (CFCCs). Such an interface is usually accomplished by the insertion of a thin coating (typically 0.1--1 {micro}m thick) such as C or BN, which is compliant enough to relieve residual clamping stresses from processing, and whose structure consists of several weakly bonded basal planes. Holmes et al. showed that in a unidirectional Nicalon/CAS composite with a weak interface, increasing loading frequency caused a significant decrease in fatigue life. Due to repeated frictional sliding of fibers, a significant amount of heat is generated by the specimen, and a large temperature rise is observed. In fact, Sorensen and Holmes have shown that immersing specimens in oil, in order to create a lubricating layer at the fiber/matrix interface, can dramatically improve the fatigue life of the composite. Following this observation of Sorensen and Holmes, the authors have hypothesized that thicker interfacial coatings may improve the fatigue life of CFCCs. To this end, Nicalon/SiC composites were examined, with a carbon coating of 0.33 and 1.1 {micro}m. The samples were identical in nature, except for themore » interfacial coating thickness.« less

Tensile behavior of irradiated SiC fibers

The strength and toughness of continuous fiber reinforced ceramic composites (CFCCs) are highly dependent on the fiber strength distribution. To first order, weaker fibers lead to low strength but higher toughness while stronger fibers lead to high strength composites of relatively low toughness. Toughness is associated with pullout of the fibers from the ceramic matrix. It has been shown previously that both strength and toughness of SiC/Nicalon TM composites are drastically changed following irradiation. Tensile results are presented for low oxygen Nicalon fibers neutron irradiated at damage levels of 0.013 displacements per atom (dpa), 0.13 dpa and 0.32 dpa. Single fibers were tensile tested and analyzed, using Weibull statistics, for mean strength and distribution. Tensile modulus was also determined. Using a diffractometer, the fiber grain size and percent crystallinity were determined. The initial results of these low fluence neutron irradiations exhibit no substantial degradation of the properties investigated. Therefore, continued research at higher doses is recommended.

Analytical Modeling in Support of the Development of Fiber Reinforced Ceramic Composite Materials for Re-Heater Burners

ABSTRACTDevelopment of Continuous Fiber reinforced Ceramic Composite (CFCC) materials is a process of identifying components which will benefit from CFCC properties, and defining appropriate composite constructions which will provide materials which will meet the structural and thermal requirements of the application. Materials Sciences Corporation (MSC) has been providing analytical support to Textron Specialty Materials in the development of re-heated tubes for metal reheating furnaces. As part of this support, a study has been made of the sensitivity of composite properties to fiber orientation as well as a number of matrix properties which control the stress-strain behavior of the composite.