Showing papers on "Ceramic matrix composite published in 2000"
TL;DR: In this article, an original catalytic method that produces ceramic-matrix composite powders that contain in situ grown nanotubes is described, and the synthesis parameters that favour the obtention of very high quantities of carbon-nanotubes are discussed.
403 citations
TL;DR: In this paper, the authors describe Si-O-C-N-B manufactured from preceramic silicon containing polymers gain in significance with increasing availability of advanced precursor materials such as poly(carbosilane), -(silazane),-(siloxane) or -(borosilazane).
Abstract: Engineering ceramics in the system Si-O-C-N-B manufactured from preceramic silicon containing polymers gain in significance with increasing availability of advanced precursor materials such as poly(carbosilane), -(silazane), -(siloxane) or -(borosilazane). While high temperature resistant Si-C and Si-N ceramic fibers are already used to reinforce ceramic matrix composites (CMC) in air- and spacecraft structures, novel products such as coatings, tapes, foams, and complex shaped components for medium and low temperature applications in the fields of energy, environmental, transportation, and communication technologies become more important in the future. Preceramic polymers offer the possibility of using versatile plastic shaping technologies as well as advanced laminated object manufacturing techniques. Properties can be varied in a wide range by tailoring the molecular structure and composition of the precursor polymer and by loading the polymer with intert or reactive filler powders. Partial conversion of the organic polymer into organic/inorganic hybrid materials yields novel materials which exhibit properties between polymers and ceramics.
308 citations
TL;DR: In this paper, a two phase oxide fibres composed of α-alumina and mullite are used for the reinforcement of ceramic matrices for use at very high temperatures.
Abstract: Two families of small diameter ceramic fibres exist. The oxide fibres, based on alumina and silica, which were initially produced as refractory insulation have also found use as reinforcements for light metal alloys. The production of SiC based fibres made possible the development of ceramic matrix composites. Improved understanding of the mechanisms which control the high temperature behaviour of these latter fibres has led to their evolution towards a near stoichiometric composition which results in strength retention at higher temperatures and lower creep rates. The SiC fibres will however be ultimately limited by oxidation so that there is an increasing interest in complex two phase oxide fibres composed of α-alumina and mullite as candidates for the reinforcement of ceramic matrices for use at very high temperatures. These fibres show low creep rates, comparable to the SiC based fibres but are revealed to be sensitive to alkaline contamination.
163 citations
TL;DR: Based on the analysis on structure of natural biomaterials, two kinds of ceramic composites with high toughness have been designed and prepared: one is fibrous monolithic Si3N4/BN composite imitating bamboos or trees in structure, the other is laminated si3N 4/BN composites imitating nacre in structure as discussed by the authors.
126 citations
TL;DR: In this article, the concept of a strong interface has been applied to SiC/SiC composites with a BN coating (referred to as siC/BN/SiCs), and fiber bonding and frictional sliding were investigated by means of push-out tests performed on 2D-composites as well as on microcomposite samples.
108 citations
TL;DR: In this paper, a model is proposed to determine the influence of an interphase on the deflection of a matrix crack in ceramic matrix composites, which is applied to a SiC/C/SiC microcomposite with a pyrocarbon interphase.
Abstract: A model is proposed to determine the influence of an interphase on the deflection of a matrix crack in ceramic matrix composites. Then, a finite element analysis is performed for a microcomposite geometry with an annular crack which initiates in the matrix and propagates in the interphase. It is applied to a SiC/C/SiC microcomposite with a pyrocarbon interphase. Criteria for penetration and deflection of the matrix crack are expressed in terms of toughness of the interphase and of the various interfaces (matrix/interphase and interphase/fibre interfaces). The predictions are found to agree with crack deflections observed in practical SiC/SiC composites and with the available interphase toughness data. Results also suggest that the real crack deflection mechanism involves debonding ahead of the propagating matrix crack.
98 citations
TL;DR: Using a preceramic polymer, joints between 2D and 3D SiC/SiCf matrix composites were obtained in this paper, where active or inert fillers were mixed with the preceramide polymer, in order to reduce its volumetric shrinkage during pyrolysis.
96 citations
TL;DR: In this paper, an oxide-based ceramic matrix composites with a highly porous mullite matrix and Nextel™ 720 alumino silicate fibers have been fabricated by infiltrating filaments with a mullite precursor slurry, and by subsequent one-dimensional and two-dimensional winding up the fiber bundles on mandrels.
Abstract: Oxide-based ceramic matrix composites with a highly porous mullite matrix and Nextel™ 720 alumino silicate fibers have been fabricated by infiltrating filaments with a mullite precursor slurry, and by subsequent one-dimensional (1D) and two-dimensional (2D)-winding up the fiber bundles on mandrels. The green bodies were pressureless sintered in air at 1300°C. These composites which require no fiber/matrix interface are characterized by favorable damage tolerance and bending strengths of 160 MPa at room temperature and up to temperatures of 1200°C. These properties make it an excellent low-cost choice for combustion chamber liners, diffusor rings and other thermal protection systems for high temperature applications in oxidizing environment.
91 citations
Patent•
18 Dec 2000
TL;DR: In this article, a ceramic matrix composite part having elongated cooling channels within the wall thereof is manufactured by inserting decomposable inserts within a woven ceramic fiber preform, where the inserts are tows of continuous carbon fibers surrounded by a carbonaceous filler and are inserted where the channels are desired.
Abstract: A ceramic matrix composite part having elongated cooling channels within the wall thereof is manufactured by inserting decomposable inserts within a woven ceramic fiber preform. The inserts are tows of continuous carbon fibers surrounded by a carbonaceous filler, and are inserted where the channels are desired. The preform, with the inserts in place, is disposed within a mold. A ceramic matrix material is added and the fiber preform is consolidated with the ceramic matrix material. The consolidated part is then heated to thermally decompose the inserts to create the elongated channels within the part. The inserts may be flexible and woven into the preform using an automated weaving loom, or they may have limited flexibility and be inserted by machine or by hand.
70 citations
TL;DR: Ali et al. as discussed by the authors used axisymmetric finite-element model to calculate axial fiber stresses versus radial position within the slipping region around an impinging matrix crack as a function of applied stress and interfacial sliding stress tau.
70 citations
TL;DR: An SiC-particulate, silicon-metal melt-infiltration-matrix composite reinforced with SiC fibers is being developed for combustor applications under the High Speed Civil Transport (HSCT) Enabling Propulsion Material (EPM) Program.
TL;DR: In this paper, a hybrid technique of chemical vapour infiltration (CVI) and polymer infiltration and pyrolysis (PIP) is proposed to fill the porosity among the fibres with SiC resulting from precursor decomposition.
TL;DR: In this paper, a process for ceramic toughening is developed, where a selected piezoelectric or ferroelectric secondary phase is incorporated and dispersed in a ceramic matrix as reinforcement.
Abstract: A process for ceramic toughening is developed, where a selected piezoelectric or ferroelectric secondary phase is incorporated and dispersed in a ceramic matrix as reinforcement. The toughening effect of Nd 2 Ti 2 O 7 secondary phase on Al 2 O 3 ceramic is determined together with the microstructures and phase constitution of the composite ceramics. Dense composite ceramics can be formed with the secondary phase and the Al 2 O 3 matrix. Compared to single phase Al 2 O 3 ceramics, the Nd 2 Ti 2 O 7 /Al 2 O 3 composite ceramic shows a significant increase in fracture toughness, and K IC reaches 6.7 MPa m 1/2 for a composition of 0.03 Nd 2 Ti 2 O 7 /0.97Al 2 O 3 .
TL;DR: In this article, the salient aspects of control of interface characteristics in oxide fiber/oxide matrix composites, with emphasis on composites consisting of alumina and mullite based oxide fibres in a variety of oxide matrixes, are reviewed.
Abstract: Oxide fibre/oxide matrix composites form an important and attractive subpart of ceramic matrix composites because of their inherent stability in oxidising atmospheres at high temperatures An important attribute of such composites, however, is that the interfacial bond between oxide matrix and oxide fibre is generally very strong, and consequently, the toughness and damage tolerance of such composites are low One way to overcome this problem is to tailor the interface such that the energy dissipating phenomena such as debonding and crack deflection at the fibre/ matrix interface, followed by fibre pullout are brought into play In this paper, the salient aspects of control of interface characteristics in oxide fibre/oxide matrix composites, with emphasis on composites consisting of alumina and mullite based oxide fibres in a variety of oxide matrixes, are reviewed
TL;DR: In this article, the authors used a single crystal monofilament (Saphikon Inc) to construct an all-oxide ceramic matrix composite (CMC) and demonstrate it in a combustor rig at conditions representative of a gas turbine engine.
Abstract: Novel oxide ceramic composites (NOCC) was a four year European programme aimed to develop an all-oxide ceramic matrix composite (CMC) and processing route, carry out a characterisation programme on the material and demonstrate it in a combustor rig at conditions representative of a gas turbine engine. The fibre used was a single crystal monofilament (Saphikon Inc.), which was chosen for its temperature and creep resistance. Alumina (aluminium oxide) was chosen for the fibre and matrix, and zirconia as a weak interphase coating on the fibre. Tape casting followed by hot pressing was chosen as the manufacturing route for the composite, with hot isostatic pressing (HIPping) as an alternative densification process. Cross-ply material with fibre volume fractions of around 30% was found to have moderate strength (100–130 MPa), but retained composite properties at elevated temperatures and after extended periods at elevated temperatures (1000 h at 1400°C). In addition, the material was found to withstand thermal cycling (>1300 cycles to 1200°C), retaining its as-fabricated properties. Computational fluid dynamics (CFD) calculations were carried out for a combustor rig, and a CMC tile was designed. The temperatures, stresses and strains in the tile were predicted using finite element (FE) analysis and combustor tiles were manufactured. A tile was successfully tested in a rig at temperatures >1260°C and up to 46 cycles. Some of the issues that remain to be addressed with the material and manufacturing method are cost, delamination during manufacture, and consistency. It is likely that, due to the high cost of the fibre and relatively modest usable strength, the material will remain as a model material. The promising results on long term static and cyclic ageing proves that the concept of an all-oxide CMC is valid and points the way to future development of this class of material.
TL;DR: In this article, a SiC fiber with a low oxygen content (Hi-Nicalon) was developed and produced commercially using an electron beam curing, which has a higher elastic modulus and creep resistance.
Abstract: Polymer-derived Nicalon SiC fiber produced commercially has been widely applied in high temperature Ceramic Matrix Composites (CMCs). Recently, SiC fiber with a low oxygen content (Hi-Nicalon) was developed and produced commercially using an electron beam curing. This fiber has a higher elastic modulus and creep resistance, and much higher thermal stability up to 1600 ° C than that of Nicalon fiber. High temperature mechanical properties of CMCs with Hi-Nicalon have much improved. However, creep and oxidation resistance of Hi-Nicalon CMCs are not satisfactory for high temperature structural materials, because Hi-Nicalon mainly consists of SiC micro-crystals and excess carbon. Therefore, we have developed an SiC fiber (Hi-Nicalon type S) with stoechiometric SiC composition and high crystallinity. Hi-Nicalon S fiber has high elastic modulus (420 Gpa), good oxidation resistance at 1400 °C, and excellent creep resistance. In this paper, the recent development of these oxygen free SiC fibres including physical and mechanical properties, thermal stability and an environmental resistance are reported.
TL;DR: In this article, a unique combination of digital image processing, microstructure modeling, and finite element (FE)-based simulations is used to develop a methodology for modeling the micro-mechanical response of composites having non-uniform spatial arrangement of fibers.
TL;DR: In this paper, 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.
Abstract: 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 degrees 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.
Patent•
18 Sep 2000
TL;DR: In this paper, a composite material includes a ceramic matrix and two different fractions of fiber bundles, namely a reinforcing fiber bundle fraction and a matrix fiber bundles having different average fiber bundle lengths.
Abstract: A composite material includes a ceramic matrix and two different fractions of fiber bundles, namely a reinforcing fiber bundle fraction and a matrix fiber bundle fraction having different average fiber bundle lengths. The fractions of fiber bundles are separated in a total fiber bundle distribution relative to a fiber bundle length by a minimum. A method for manufacturing a composite material and a method for manufacturing elements formed of a composite material are also provided.
TL;DR: In this paper, the authors measured the electrical conductivity and Seebeck coefficient of the B 4 C and B 4C-W 2 B 5 composite ceramics from room temperature up to 1500 K.
TL;DR: In this article, near fully dense in situ ceramic matrix composites were fabricated from blends of fine Ti-B 4 C, Ti-BN, Ti−SiC, Ti•B 6 Si and Al-TiO 2 powders without or with the addition of Ni.
TL;DR: In this paper, an experimental investigation was performed to study the rate at which strength-controlling fatigue damage evolves in a ceramic-matrix composite, and the fracture surfaces of the specimens cycled to failure had a central region where fiber pullout was negligible.
Abstract: An experimental investigation was performed to study the rate at which strength-controlling fatigue damage evolves in a ceramic-matrix composite. Tensile specimens of a unidirectional SiC-fiber-reinforced calcium aluminosilicate matrix composite were cycled to failure or to a preselected number of cycles under similar loading histories. The residual strength of the precycled specimens was found to be similar to that of virgin specimens. Microstructural investigations showed that the fracture surfaces of the specimens cycled to failure had a central region where fiber pullout was negligible. It is proposed that frictional heating (due to interfacial sliding) is the cause of fatigue failure. High interfacial temperatures are assumed to cause the formation of a strong interface bond, leading to internal embrittlement.
TL;DR: In this paper, the tensile creep and fracture properties in air at 1300°C were compared for SiCf/SiC and SiCc/Al2O3 composites, each reinforced with 038 volume fractions of interwoven silicon carbide (Nicalon™) fibre bundles aligned parallel and normal to the stress direction.
Abstract: The tensile creep and creep fracture properties in air at 1300°C are compared for SiCf/SiC and SiCf/Al2O3 composites, each reinforced with 038 volume fractions of interwoven silicon carbide (Nicalon™) fibre bundles aligned parallel and normal to the stress direction The differing behaviour patterns displayed by these 0/90° woven composites are analysed to identify the processes controlling creep strain accumulation and crack development
TL;DR: In this article, SiC fibers with high mechanical and good thermal properties are suitable as reinforcements of composite materials. And they are regarded highly in the reinforcement of ceramic matrix composites (CMCs), mainly because of their excellent high temperature properties.
Abstract: Silicon carbide (SiC) fibers with high mechanical and good thermal properties are suitable as reinforcements of composite materials. Among the various kinds of reinforcements, SiC fibers are regarded highly in the reinforcement of ceramic matrix composites (CMCs), mainly because of their excellent high temperature properties. SiC fibers produced via polymer pyrolysis especially have the advantage of flexible, fine-diameter form over those from chemical vapor deposition (CVD) or powder sintering processes. SiC fibers, such as Nicalon and Tyranno, synthesized from organosilicon polymers, have been produced industrially and applied widely to heat-resistant materials and to the reinforcements for composite materials.
01 Jan 2000
TL;DR: In this article, 10 different ceramic matrix composite (CMC) materials were subjected to a constant load and temperature in an air environment, at a temperature of 1454 deg C at stresses of 69 MPa, 172 MPa and 50% of each material's ultimate tensile strength.
Abstract: : Ten different ceramic matrix composite (CMC) materials were subjected to a constant load and temperature in an air environment. Tests conducted under these conditions are often referred to as stressed oxidation or creep rupture tests. The stressed oxidation tests were conducted at a temperature of 1454 deg C at stresses of 69 MPa, 172 MPa and 50% of each material's ultimate tensile strength. The ten materials included such CMCs as C/SiC, SiC/C, SiC/SiC, SiC/SiNC and C/C. The time to failure results of the stressed oxidation tests will be presented. Much of the discussion regarding material degradation under stressed oxidation conditions will focus on C/SiC composites. Thermogravimetric analysis of the oxidation of fully exposed carbon fiber (T300) and of C/SiC coupons will be presented as well as a model that predicts the oxidation patterns and kinetics of carbon fiber tows oxidizing in a nonreactive matrix.
TL;DR: In this article, a fiber-reinforced mullite-based matrix fabricated by Dornier Forschung at DLR Institute of Materials Research was characterized at the DLR and the modulus of the composite was analyzed on the basis of the expected moduli of the fibres and the mullite matrix.
Abstract: Nextel 610 fibre-reinforced mullite-based matrix fabricated by Dornier Forschung was characterised at DLR Institute of Materials Research. The material was produced by the polymer route after coating the fibres with a 0.1 μm thick carbon layer. The composite was manufactured by infiltrating the fibres with a slurry containing a diluted polymer and mullite powder, curing in an autoclave and subsequently heat treating and pyrolysis of the polymer. A final heat treatment in air is performed to remove the carbon coating and to reduce the residual stresses. A (0/90/0/90/0/90) s -laminate was produced with an average fibre volume fraction of 45.6% and a porosity of 15.9%. Dog-bone-type tensile specimens with a width of 10 mm were cut from the plate by water jet and tested at temperatures up to 1200°C in air. The tensile strength at room temperature measured 177.4 MPa and linearly decreased to 145.2 MPa at a temperature of 800°C. A stronger decrease occurred at 1000 and 1200°C. In contradiction to ceramic matrix composites manufactured by the CVI-route the stress–strain behaviour is nearly linear up to failure. The modulus of the composite (at room temperature 108.8 GPa) is analysed on the basis of the expected moduli of the fibres and the mullite matrix. It can be concluded that the contribution of the matrix to the modulus of the composite is low, caused by porosity and components other than mullite. The intralaminar shear strength at room temperature measured 36 MPa. This value reflecting shear transfer capability of fibre to matrix limits the amount of fibre pull-out.
Patent•
18 Aug 2000
TL;DR: In this paper, a composite ceramic including a first phase of ceramic material and a second phase of composite material, the first and second phases forming three dimensional interconnected networks of each phase and having a nano-scaled grain size, is produced in a method which utilizes rapid solidification at cooling rates of at least ∩104°K/sec to produce a metastable material formed by a solid solution of a two immiscible ceramic material phases, and also utilizes relatively high pressure/low temperature consolidation to complete densification of the metastable materials, while simultaneously generating a composite structure with
Abstract: A composite ceramic including a first phase of ceramic material and a second phase of ceramic material, the first and second phases forming three dimensional interconnected networks of each phase and having a nano-scaled grain size. The composite ceramic is produced in a method which utilizes rapid solidification at cooling rates of at least ∩104°K/sec to produce a metastable material formed by a solid solution of a two immiscible ceramic material phases, and which also utilizes relatively high pressure/low temperature consolidation to complete densification of the metastable material, while simultaneously generating a composite structure with nano-scale grain dimensions through a controlled phase transformation.
TL;DR: In this article, the physical state of the fiber/matrix interface is governed by the physical states of the composite, e.g., during loading, the chemical bonds which develop between fiber and matrix during processing, are broken.
Abstract: When ceramic matrix composites are subjected to fatigue loading levels sufficient to initiate microstructural damage to the constituents, the mechanical response of the laminate, e.g. the residual strength, stiffness and life of the composite, is governed by the physical state of the fiber/matrix interface. During loading, the chemical bonds, which develop between fiber and matrix during processing, are broken. This 'debonding' results in a significant decline in load transfer between the two constituents and leads to a measurable increase in laminate compliance. With continued cyclic loading, the interface debonds grow in length which further degenerates the composite strength. Moreover, within the debonded regions, frictional sliding between the fiber and matrix is permitted and leads to surface wear of the constituents [1]. Ultimately, the progression of this damage mode leads to a further decline in the interfacial shear stress and load transfer between the constituents. Knowledge of the progression o...
TL;DR: In this article, a two-dimensional woven SiC/SiC ceramic matrix composite (CMC) under tensile loading is modeled by regarding a three-dimensional unit cell of the composite which takes the waveness of the fiber yarns in two directions into account.
15 Apr 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure, mechanical properties, fracture behavior and toughening mechanisms of the composites were investigated by scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution electron microscope (HREM), X-ray photo spectroscopy (XPS), energy dispersive analysis of Xray (EDAX) techniques and three-point bending tests.
Abstract: Al2O3–20vol%SiCw composites with as-received and acid-leached whiskers were fabricated by a hot-pressing technique. The microstructure, mechanical properties, fracture behavior and toughening mechanisms of the composites were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), X-ray photo spectroscopy (XPS), energy dispersive analysis of X-ray (EDAX) techniques and three-point bending tests. The results show that whisker surface acid-leached treatment obviously reduces the oxygen content of SiC whisker and makes the whisker surface smooth, resulting in composites with higher fracture toughness.