Quantification of energy absorption by fibre pull-out during failure of SiCf/BN/SiBCN ceramic matrix composites

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.

Ceramic matrix composites (CMCs) are a class of high temperature materials with better damage tolerance properties compared to monolithic ceramics. The improved toughness is attributed to weak interface coating between the fiber and the matrix that allows for crack deflection and fiber pull-out. Thus, CMCs have gained consideration over monolithic materials for high temperature applications such as in gas turbines. The current standard fiber architecture for CMCs is a harness satin (HS) balanced weave (5HS and 8HS); however, other architectures such as uni-weave materials (tape layup) are now being considered due to fiber placement control and higher fiber volume fraction in the tensile loading direction. Engineering components require additional features in the CMC laminates, such as holes for attachments. Past work has shown that acoustic emission could differentiate the effect of changing interface conditions due to heat treatment effects. The focus of the present work is to investigate the effects of different weaves and the presence of a feature on damage behavior of CMCs as observed via acoustic emission technique. The results of the tensile testing with acoustic emission monitoring will be presented and discussed.Ceramic matrix composites (CMCs) are a class of high temperature materials with better damage tolerance properties compared to monolithic ceramics. The improved toughness is attributed to weak interface coating between the fiber and the matrix that allows for crack deflection and fiber pull-out. Thus, CMCs have gained consideration over monolithic materials for high temperature applications such as in gas turbines. The current standard fiber architecture for CMCs is a harness satin (HS) balanced weave (5HS and 8HS); however, other architectures such as uni-weave materials (tape layup) are now being considered due to fiber placement control and higher fiber volume fraction in the tensile loading direction. Engineering components require additional features in the CMC laminates, such as holes for attachments. Past work has shown that acoustic emission could differentiate the effect of changing interface conditions due to heat treatment effects. The focus of the present work is to investigate the effects of ...

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.

Advances in Ceramic Matrix Composites

Near-net-shape fibre-reinforced ceramic matrix composites by the sol infiltration technique

Reliable design of ceramic matrix composite components in aerospace applications requires the knowledge of the crack propagation behavior of these materials at elevated temperatures. The first part of this paper discusses a test setup using a centrally notched disk to conduct mechanical fatigue crack growth testing of brittle matrices used in these composites. The specimen compliance is monitored using the laser interferometric displacement gage system. To evaluate this fatigue crack growth test setup, cyclic crack propagation is studied in an alumina ceramic specimen. Transmission electron microscopy of surface replicates show evidence of irreversible microcracking at the crack tip that could provide the mechanism for fatigue crack growth in this ceramic. The second part of this paper discusses the results from automated fatigue crack growth tests on silicon-carbide fiber-reinforced aluminosilicate glass matrix composites at room and elevated temperatures using the compact tension geometry. Tests conducted at room temperature indicate high damage tolerance in these composites due to energy dissipation through distributed matrix cracking around the tip, fiber bridging, and fiber pull out. In contrast, tests at 650°C reveal Mode 1 self-similar crack growth in these composites and absence of fiber pullout.

Ceramic matrix composites (CMCs) are a promising subclass of composite materials suitable for high temperature applications. CMCs exhibit multiple damage mechanisms such as matrix cracking, interphase debonding, fiber sliding, fiber pullout, delaminations etc. Additionally, process induced defects such as matrix porosity exists at multiple length scales and has a considerable influence on the mechanical and failure behavior of CMCs. In the current work, the effect of intra-tow porosity, which exist at the micro-scale, on the mechanical behavior of CMCs has been investigated by numerical homogenization. Micro-scale response of 3 phase CMCs with intra tow pores has been obtained by finite element analysis based homogenization. Pores have been modeled as non-intersecting ellipsoids in a square unit cell representative of matrix material. The effective mechanical properties of porous matrix at the micro scale has been obtained from numerical homogenization, which are in good agreement with Mori-Tanaka mean field theory. The obtained matrix elastic properties have then been included in a three phase unit cell consisting of fiber, interphase and matrix representative of CMC microstructure. The effect of porosity volume fraction and aspect ratio on the effective elastic properties of the composite have been reported. Homogenization approach to model statistical distribution of pore size obtained from X-ray computed tomography of CMC minicomposite has been proposed.

Ceramic Matrix Composites (CMC) are widely used for manufacturing automobile parts aircraft components, biomedical and electronic devices. In recent years, graphene has found extensive applications in various fields like effective reinforcement in the development of metal matrix, polymer matrix and ceramic matrix composites. Literature reveals that more focus was on polymer and metal matrix composites reinforced with graphene when compared to ceramic matrix composites. In this manuscript, the effect and suitability of graphene as a reinforcement for fabricating ceramic matrix composite are presented. Further, the property evaluation, including mechanical and physical, characterization and microstructural evaluation of the CMCs developed with graphene as reinforcement is elaborated. The investigation of the reinforcing mechanisms and failure behavior of ceramic matrix composites reinforced with graphene, together with the development of novel processing techniques to solve manufacturing difficulties, are key areas of focus. Although many investigations have concentrated on enhancing the mechanical and electrical characteristics of ceramics by integrating graphene, more investigation is required to investigate the interfacial interaction between graphene and the ceramic matrix, as well as the influence of graphene size on the properties of the composite. Furthermore, there is a need for future research to explore the possibility of using graphene-reinforced ceramic composites in several multifunctional applications, including microwave absorption, electromagnetic interference shielding, ballistic armors, self-monitoring damage sensors, and energy storage and conversion. Future research should focus on developing innovative processing procedures that guarantee the uniform distribution and precise alignment of graphene sheets within the ceramic matrix. The incorporation of graphene into ceramic matrix composites presents novel prospects for augmenting the characteristics and capabilities of ceramics, rendering it a very interesting area for further investigation.

This paper addresses the application of ultrasonic methods to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock and oxidation at elevated temperatures. The damage-induced changes in elastic constants and elastic anisotropy are determined by measuring the velocities of ultrasonic waves in different propagation directions within the sample. Thermal shock damage measurement is performed in ceramic samples of reaction bonded silicon nitride (RBSN) and aluminum oxide. Thermal shock treatment from different temperatures up to 1000°C is applied to produce the microcracks. Both surface and bulk ultrasonic wave methods are used to correlate the change of elastic constants to microstructural degradation and to determine the change in elastic anisotropy induced by microcrack damage. Oxidation damage is studied in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400°C, for 100 hours. Significant changes of ultrasonic velocities were observed for composites before and after oxidation. The elastic constants of the composites were determined from the measured velocity data. The Young’s modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600°C but retains its original value at temperatures above 1200°C. This agrees well with the results of destructive tests by other authors. The transverse longitudinal and shear moduli obtained from ultrasonic measurements decrease continually until 1200°C. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

This paper addresses the application of ultrasonic methods to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock and oxidation at elevated temperatures. The damage-induced changes in elastic constants and elastic anisotropy are determined by measuring the velocities of ultrasonic waves in different propagation directions within the sample. Thermal shock damage measurement is performed in ceramic samples of reaction bonded silicon nitride (RBSN) and aluminum oxide. Thermal shock treatment from different temperatures up to 1000°C is applied to produce the microcracks. Both surface and bulk ultrasonic wave methods are used to correlate the change of elastic constants to microstructural degradation and to determine the change in elastic anisotropy induced by microcrack damage. Oxidation damage is studied in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400°C, for 100 hours. Significant changes of ultrasonic velocities were observed for composites before and after oxidation. The elastic constants of the composites were determined from the measured velocity data. The Young’s modulus in the fiber direction as obtained from ultrasonic measurements decrases significantly at 600°C but retains its original value at temperatures above 1200°C. This agrees well with the results of destructive tests by other authors. The transverse longitudinal and shear moduli obtained from ultrasonic measurements decrease continually until 1200°C. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

Ceramic matrix composites (CMCs) are widely used in aerospace, defense industry, and other fields because of their high strength, high toughness, and high temperature resistance. The interface phase with matching performance and structural coordination is the key element to improve the brittleness of CMCs and improve their strength and toughness. In this chapter, based on the fiber pull-out experiment, using the cohesive zone model as the interface element model, a two-dimensional axisymmetric fiber pull-out finite element model was established and simulated. The results show that within a certain range, higher interface bonding strength and interface fracture energy increase the maximum debonding load during fiber pull-out and enhance the material bearing capacity.

Ceramic matrix composites (CMCs) are being developed to take advantage of the high-temperature properties of ceramics while overcoming the low fracture toughness of monolithic ceramics. Toughening mechanisms, such as matrix cracking, crack deflection, interface debonding, crack-wake bridging and fiber pullout, are being incorporated in CMCs to reduce the tendency for catastrophic failure found in monolithic ceramics. Ceramics reinforced with particulate, whiskers and continuous fibers exhibit varying aspects of these toughening mechanisms; however, reinforcement with continuous fibers offers the greatest improvements in toughness. Composites with carbide, oxide, glass and carbon matrices are being utilized in the development of CMCs. In the case of carbide, oxide and glass matrix CMCs, the matrix exhibits excellent high-temperature corrosion resistance so that a goal of the composite development is to not detract from this pre-existing property. This is not the case for carbon matrix composites which frequently need coatings to provide adequate corrosion protection. The purpose of this chapter is to review the database and understanding of corrosion behavior of CMCs with the intent that this information will be useful in the development of materials with improved performance and reliability.

Oxidation and corrosion of ceramics and ceramic matrix composites

This article describes a theoretical model and an experimental method for determination of interphasial elastic moduli in high-temperature composites. The interphasial moduli are calculated from the ultrasonically measured composite modulivia inversion of multiphase micromechanical models. Explicit equations are obtained for determination of interphasial stiffnesses for an interphase model with spring boundary conditions and multiphase fiber. The results are compared with the exact multiphase representation. The method was applied to ceramic and intermetallic matrix composites reinforced with SiC SCS-6 fibers. In both composites, the fiber-matrix interphases include approximately 3-μm-thick carbon-rich coatings on the outer surface of the SiC shell. Although the same fiber is used in both composite systems, experimental results indicate that the effective interphasial moduli in these two composite systems are very different. The interphasial moduli in intermetallic matrix composites are much greater than those in ceramic matrix composites. After taking the interphase microstructure into account, we found that the interphasial moduli measured for the intermetallic matrix composites are very close to the estimated bulk moduli of the pyrolytic carbon with SiC particle inclusions. Our analysis shows that the lower effective interphasial moduli in the reaction-bonded Si3N4 (RBSN) ceramic matrix composites are due to imperfect contact between the interphasial carbon and the porous matrix and to thermal tension forces which slightly unclamp the interphase. Thus, measured interphase effective moduli give information on the quality of mechanical contact between fiber and matrix. Possible errors in the interphasial moduli determined are analyzed and the results show that these errors are below 10 pct. In addition, the use of the measured interphasial moduli for assessment of interphasial damage and interphase reactions is discussed.

Environment induced crack growth of ceramics and glasses