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VENTRELLA, ANDREA. "JOINING OF CERAMIC COMPOSITES AND ADVANCED CERAMICS." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2502686.
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Ceramics and Ceramic Matrix Composites (CMC) are well known as useful materials for harsh environment applications. Ceramic components have been widely used as abrasives, cutting tools, nuclear fuel elements, catalyst supports and astronomical telescope mirrors. Generally speaking, ceramics and CMC are excellent candidates for high-temperature applications because of their good mechanical properties and thermal stability at elevated temperatures.
However, to produce large-size and complex components, development and testing of joints for ceramics and CMC are fundamental. Joining materials and techniques currently available to join ceramic and CMC include diffusion bonding using various active fillers, transient eutectic phase methods such as nano-infiltration and transient eutectic-phase (NITE), laser joining, selected area chemical vapor deposition , glass-ceramic joining , solid state displacement reactions, preceramic polymer routes, reaction forming, brazing. Adhesive joining materials (e.g. epoxy resins) are used to join ceramics only for applications at temperature lower than 150 °C, i.e. adhesively bonded joints are widely used for automotive, aerospace, electronic and packaging applications.
Together with the need of a reliable joining method, a widely accepted standard to test the mechanical strength of joined ceramics and composites is still unavailable and measuring the shear strength of the same joining material with different test methods could lead to different results.
The aim of this Thesis is to compare and discuss several different shear strength tests used to join ceramics and CMC, with the final goal to provide designers and scientific community a widely accepted, reliable test method.
A homogeneous pure shear stress state is not obtainable with most of the currently used single or double lap tests, which give apparent and not pure shear strength of the joined samples; in addition, the presence of several different apparent shear strength tests in the literature makes comparison quite impossible.
The asymmetrical four point bending test (ASTM C1469-10) is recommended as a standard test by the ASTM to test joined ceramics and composites, but notches have to be cut in the joined area when the joining material strength is high. When the shear strength of the joining material approaches that of the substrate to be joined, ASTM C1469-10 is not suitable.
With torsion tests a pure shear loading strength can be measured without using notches.
One of the very first proposals for torsion test for epoxy bonded aluminum alloy samples was reported by M. Ouddane et al.: as thoroughly discussed there, torsion results were considered more reliable than those obtained by standard lap tests, the improvement mainly due to the fact that lap tests induce non uniform stress concentrations that affect the reliability of results.
Recent papers deal with torsion tests on joined hourglass shaped samples : preliminary results suggest that the torsion test method with a miniature specimen has a potential to evaluate the shear properties of the joint interface, provided that the fracture occurs in the joined area.
Torsion tests have been thoroughly analyzed in this Thesis: a pure non-uniform shear stress distribution is obtained with torsion tests; together with asymmetrical four point bending test (ASTM C1469-10), torsion test is the only one able to measure pure shear strength of joined ceramics and composites.
The torsion test method is proposed in some ASTM standards but none of them is directly applicable to joined ceramics: the main result of this Thesis is to demonstrate the reliability of torsion as a method to measure the shear strength of joined ceramics and CMC.
Two torsion standards have been adapted to joined C/C and ceramics, first by preparing square section samples (TS), rods (TC), tubes (TT), then by mechanically shaping the joined samples as a hourglass in different shapes.
The choice of an epoxy resin (Araldite AV119) to join SiC in this PhD thesis was done in order to have a “model” brittle joining material to obtain a statistically relevant number of joined samples in a reasonable time, to compare shear strength results .
More than one hundred joined samples have been prepared and tested at room temperature by asymmetrical four point bending (A4PB) (ASTM C1469-10), torsion on square section samples (TS), torsion on circular section rods (TC), torsion on hourglass shaped samples (THG, TDHG, TRHG), torsion of tubes (TT), single lap in compression (SL), single lap off set in compression (SLO), double lap off set in compression (DLO), Brazilian test (BT), double notch (DN) methods. A modified ASTM B898 standard has been used as a further example of single lap test in compression to complete the comparison work (B898).
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Feilden, Ezra. "Additive manufacturing of ceramics and ceramic composites via robocasting." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/55940.
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In the last two decades additive manufacturing (AM) has emerged as a highly important and influential technology. A large range of approaches to AM have been developed which give rise to hundreds of distinct techniques. Many of these are specific to one material system, and only a handful have been successful at producing ceramic parts. Robocasting is one such technique, having been used to produce complex ceramic parts with reasonable mechanical properties. In this thesis robocasting is investigated further, firstly by characterising the rheology of the robocasting paste, and then by measuring the strength and reliability of ceramic parts produced by robocasting. The critical defects associated with the process are identified, and efforts have been made to eliminate them. Furthermore, it was possible to produce a new class of ceramic composites consisting of alumina platelets aligned by the shear forces that arise during printing. These platelets themselves and the composites were extensively characterised. A new in-situ double cantilever test was developed in order to study the fracture behaviour of the composites. Lastly, the principle of using the printing process to align platelets was applied to fibres in order to create printed fibre reinforced ceramic matrix composites, and printed carbon fibre reinforced epoxy.
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Fu, Yu. "Residual Strength of Metal Particulate Reinforced Ceramic Matrix Composites with Multiple Cracks." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/FuY2008.pdf.
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Edrees, Hamza J. "Sialon ceramic matrix composites." Thesis, University of Strathclyde, 1990. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21383.
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The present study has been performed on β'-sialon matrix reinforced with either carbon fiber, metals or TiN components. The study describes the optimum methods of fabrication of these composites and also investigates their mechanical and electrical properties. In carbon fiber/sialon system, reaction between the fiber and the matrix has been identified and overcomed by applying high densification rate and low temperature sintering. Samples containing 10-20V% fiber was hot pressed to almost theoretical density at temperatures 1500-1550°C. In metal reinforced sialon matrix composites there is always a reaction between the metal and the sialon to form metal silicide liquid at relatively low temperatures, which is found to be helpfull in decreasing the maximum densification temperature. Sialon reinforced by 15V% Ni powder is pressureless sintered to over 95 % of the theoretical density at temperature of 1450°C. Reaction in such composites can be controlled by increasing the sintering heating rate and the amount of silicon metal dissolveed into the metal particles (which strongly influences the composites mechanical properties) can be controlled by a two stage heat treatment sintering particularly in the stainless steel/sialon system. The addition of TiN to sialon matrix resulted in processing with no troubles of chemical incompatibility and composites with attractive mechanical properties. Density of almost theoretical was achieved in the addition of 10-30V%TiN to sialon. The crack type investigations on sialon and sialon matrix composites shows that the cracks are of Palmqvist type. The indentation fracture toughness of the composites mentioned above is dependant on the reinforced phase type, volume fraction and sintering temperature. In fiber/sialon composites fracture toughness of 4 7.9 MNm⁻³/² was achived by hot pressing 15V% carbon fiber/sialon composites. In metal/sialon composites, however, fracture toughness of 13 MNm⁻³/² is achieved, whilst the indentation fracture toughness of 30V%TiN reinforced sialon composites is 8.9 MNm⁻³/². The electrical conductivity of these composites is strongly dependant on the reinforced phase volume fraction and most importantly on the particles size of the conductive phase. However, resistivity of 0.5 Ω. cm is achieved in the addition of 20V% carbon to the sialon matrix. In metal/sialon systems resistivity of 3.37 Ω. cm is achieved in 20V% Ni/sialon composite whilst 30V%TiN is required to create a resistivity of 443 Ω. cm in such composites.
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Lev, Leonid C. (Leonic Charles). "High temperature ceramic composites." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38078.
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Antti, Marta-Lena. "All-oxide ceramic matrix composites." Doctoral thesis, Luleå, 2001. http://epubl.luth.se/1402-1544/2001/34/index.html.
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Ferraro, Claudio. "Bio-inspired ceramic based composites." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45538.
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The progress of a wide range of strategic fields from aerospace, construction, transportation or medicine depends on the ability to develop new materials combining different structural and functional properties, from lightweight to high fracture resistance. One way of achieving this is by borrowing design principles found in Natural materials such as bone or nacre and integrating them into man-made materials. A common characteristic of these Natural composites is the combination of hard and soft phases in hierarchical structures with characteristic dimensions spanning multiple length scales. The process of adapting natural structural features to new technologies is called “bio-inspiration”. This PhD project, attempts to mimic some of the structural motifs found in natural materials to produce innovative lightweight ceramic structures and ceramic-based composites with high fracture resistance. Freeze casting (also known as ice-templating) was used to produce strong and lightweight SiC scaffolds using SiC particles with two different morphologies: spherical nanoparticles (400 nm in diameter) and micro-fibres (~18 μm long and ~1.5 μm in diameter). In both cases the optimal rheological behaviour for the freeze casting slurries along with optimal sintering conditions for the consolidation of the freeze cast scaffolds have been identified. Freeze casting of nanoparticle suspensions resulted in porous layered scaffolds with wavelengths (lamella wall plus pore space) ranging from ~60 to ~15 microns and porosity between ~50% and ~75%. The packing of fibres during freeze casting allowed the formation of highly porous networks with porosities as high as 98%. The mechanical (compressive and flexural strength) and functional properties (electrical conductivity, thermal conductivity) of the scaffolds have been measured and related to their structure. These scaffolds have been employed as preforms to produce SiC based composites through infiltration of the residual porosity with two different polymers: PMMA and Epoxy resin. The distinctive layered architecture of the composites enables a combination of high flexural strength and fracture resistance. The main toughening mechanisms (crack deflection, crack bridging, plastic deformation etc.) have been identified. To form metal-ceramic composites, layered freeze cast alumina preforms have been infiltrated with an aluminium alloy (Al-4Mg). The wettability of this alloy on alumina allows the infiltration of porous scaffolds without the application of external pressure. Therefore an extremely porous preform can be fully infiltrated without damaging the ceramic network. The microstructures of alumina preforms obtained from nanoparticles (400nm in diameter) or platelets (5-10μm in diameter and 300-500nm in thickness) have been compared. The use of platelets enables the fabrication of layered ceramic scaffolds with wall thickness of ~5-6μm. Mechanical tests revealed that the layered freeze casted composites exhibit a combination of high fracture resistance and flexural strength, with values that are superior to other metal-ceramic composites. Materials fabricated using alumina platelets can reach the strengths up to ~890MPa. All the materials exhibit stable crack propagation with a characteristic R-curve. An extensive study of crack interaction with the microstructural features has been performed to identify the key toughening mechanisms such as crack deflection, crack bridging, micro-cracking and plastic deformation. The results of this thesis suggest that the structure of natural materials can be used as a blueprint in the development of new advanced composites. This requires processing techniques able to implement, in practical dimensions, the design concepts found in natural materials. However, a deep understanding of the relationships between structure and mechanical response encompassing the influence of structural parameters acting at multiple length scales is still needed to guide this effort.
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Sujirot, Kuljira. "Silicate glass-ceramics containing fluoride for application in ceramic-matrix-composites." Thesis, Imperial College London, 1995. http://hdl.handle.net/10044/1/7435.
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Matthews, Stephen John. "Cavitation erosion of aluminium alloys, aluminium alloy/ceramic composites and ceramics." Thesis, Coventry University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317927.
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Shrestha, Amit K. "Synthesis and characterization of ceramic composites." Menomonie, WI : University of Wisconsin--Stout, 2006. http://www.uwstout.edu/lib/thesis/2006/2006shresthaa.pdf.
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Ironside, K. I. "Damage in woven ceramic matrix composites." Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/842778/.
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The mechanical behaviour of woven fabric-based continuous silicon carbide fibre reinforced Pyrex (SiC/Pyrex) and calcium alminosilicate (SiC/CAS) matrix composites under quasi-static and cyclic tensile loading has been investigated. Both a plain weave and a satin weave architecture were examined for each material type. Under quasi-static loading for all systems except the low temperature processed Pyrex system (which failed prematurely) a linear elastic region was observed up to an applied strain of 0.04-0.06%. Above this strain (the matrix microcracking threshold) a reduction in the composite modulus was seen. The reduction in composite stiffness is attributed to matrix microcracking, and the morphology of matrix microcracking was examined and quantified using an edge replication technique. In all systems the matrix microcrack density was seen to increase approximately linearly with increasing strain up to failure. The corresponding reduction in the composite modulus at failure was 40-50%. Associated with the damage there is hysteretic behaviour and an increasing residual strain. The strain to failure of the satin weave composites was higher than the plain weave composites. In the cyclic fatigue tests the number of cycles to failure decreased with increasing peak stress level. A progressive reduction in the composite modulus was seen with cycles even when the applied strain was below the matrix microcracking strain threshold. It is likely that at strains below this threshold there is non-interacting matrix microcracking which does not initially affect the composite modulus. However, on continued tensile fatigue cycling these microcracks grow through a possible sub-critical crack growth mechanism reducing the laminate modulus. A modified shear lag model was used to model the reduction in composite stiffness as a function of the measured matrix crack density. The woven composite was converted to an equivalent cross-ply sub-laminate on to which the matrix microcracks were superimposed. A model allowing for the presence of microcracks in both the matrix and transverse plies gave the best agreement between the experimental and predicted reduction in modulus.
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Yttergren, Rose-Marie. "Mechanical properties of laminated ceramic composites /." Stockholm : Tekniska högsk, 1999. http://www.lib.kth.se/abs99/ytte0910.pdf.
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Kooner, Surinder. "Interfacial properties of glass-ceramic composites." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386639.
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Lawrence, Charles W. "Acoustic microscopy of ceramic fibre composites." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281057.
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Zhe, Xiaoli. "Novel zirconium oxide-based ceramic composites." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366774.
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Ellerby, Donald Thomas. "Processing and mechanical properties of metal-ceramic composites with controlled microstructure formed by reactive metal penetration /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10583.
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Laurie, Joyce. "Freeze casting : a modified sol-gel process." Thesis, University of Bath, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260248.
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Das, Satyajit. "Mechanics of 3D composites." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271189.
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This thesis contributes towards understanding of mechanical response of 3D composites and ceramics. Composite materials have widespread applications ranging from aerospace, civil sectors to sports and drones. One important application is in composite armours where composites and ceramic layers are used together. Therefore, it is important to study the mechanical response of these components to develop better armour systems. The first part of this thesis concerns with dynamic penetration response of confined ceramic targets. In the second part, mechanics of a novel 3D composite consisting of orthogonal carbon fibre tows is studied. The dynamic penetration of ceramic target by a long-rod projectile is studied using a mechanism based ceramic constitutive model. This is to capture and explain the essential physics observed during penetration of a ceramic target such as dwell and structural size effect. Dwell is captured using the constitutive model and the related physics is studied along with identification of causes of dwell. Origins of structural size effect in ceramics are identified and their influences are studied. In the second part of the thesis a novel 3D composite consisting of three mutually perpendicular orthogonal tows is studied under compression, indentation and three-point bending. Under compression along low fibre volume fraction direction (Z), the 3D composite forms stable and multiple kinks in the Z tows resulting in 10% ductility. This contrasts with traditional UD or 2D composites which fail catastrophically at 2% strain. The stability in the case of the 3D composite is due to the constraint imposed by the surrounding material. Under indentation, the 3D composite has a near isotropic and ductile response. In contrast, traditional cross-ply composites show highly anisotropic response where indentation results in brittle failure along in-plane direction. Under three-point bending, the response was ductile in Z-direction and brittle in other two directions. Overall, the 3D composite studied in this thesis shows improvement over traditional CFRPs in ductility and energy absorption capability. The 3D composite has been demonstrated to have smooth load-displacement curves reminiscent to indentation of metal in all three directions achieved at densities significantly lower than structural metals that display equivalent ductility. Thus, these 3D composites are strong candidates for applications where loading direction is unknown a-priori, and where high energy absorption is required along with reusability of the material.
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Huang, Xinyu. "Mechanics and Durability of Fiber Reinforced Porous Ceramic Composites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26063.
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Porous ceramics and porous ceramic composites are emerging functional materials
that have found numerous industrial applications, especially in energy conversion
processes. They are characterized by random microstructure and high porosity.
Examples are ceramic candle filters used in coal-fired power plants, gas-fired
infrared burners, anode and cathode materials of solid oxide fuel cells, etc.
In this research, both experimental and theoretical work have been conducted to
characterize and to model the mechanical behavior and durability of this novel
class of functional material. Extensive experiments were performed on a hot gas
candle filter material provided by the McDermott Technologies Inc (MTI). Models at
micro-/meso-/macro- geometric scales were established to model the porous ceramic
material and fiber reinforced porous ceramic material. The effective mechanical
properties are of great technical interest in many applications. Based on the
average field formalism, a computational micromechanics approach was developed to estimate
the effective elastic properties of a highly porous material with random microstructure.
A meso-level analytical model based on the energy principles was developed to estimate
the global elastic properties of the MTI filament-wound ceramic composite tube.
To deal with complex geometry, a finite element scheme was developed for
porous material with strong fiber reinforcements. Some of the model-predicted elastic
properties were compared with experimental values. The long-term performance of ceramic
composite hot gas candle filter materials was discussed. Built upon the stress analysis
models, a coupled damage mechanics and finite element approach was presented to assess
the durability and to predict the service life of the porous ceramic composite
candle filter material.Ph. D.
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Marriner-Edwards, Cassian. "The development of fibre-reinforced ceramic matrix composites of oxide ceramic electrolyte." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:3af11d08-c0d8-429b-8eab-d2befc83ea74.
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Flammable solvents contained in liquid electrolytes pose a serious safety risk when used in lithium batteries. Oxide ceramic electrolytes are a safer alternative, but suffer from inadequate mechanical properties and ionic conductivity. Thin electrolyte layers resolve the issue of conductance, but accentuate the detrimental mechanical properties of oxide ceramics. The presented work has investigated oxide ceramic electrolyte reinforcement in composite electrolytes for all-solid-state batteries. Fabricating oxide ceramic electrolytes with engineered microstructure enabled development of a reinforced composite. This approach is based on the formation of 3D- porous ceramics via stereolithography printing of polymer templates from designed cubic, gyroid, diamond and bijel architectures. The microstructural parameters of templates were analysed and modified using computational techniques. Infiltration of the prepared 3D-porous electrolyte with polymeric-fibre reinforcement created the reinforced composite electrolyte. The prepared ceramic composite showed excellent reproduction of the template microstructure, good retention of ionic conductivity and enhanced mechanical properties. The final composite was composed of NASICON-type Li1.6Al0.6Ge1.4(PO4)3 oxide ceramic electrolyte and epoxy and aramid fibre reinforcement. The gyroid architecture was computationally determined as having the optimal stress transfer efficiency between two phases. The printed gyroid polymer template gave excellent pore microstructure reproduction in ceramic that had 3D-interconnected porosity, high relative density and the most uniform thickness distribution. The ceramic matrix porosity allowed for complete infiltration of reinforcement by aramid and epoxy forming the fibre-reinforced ceramic matrix composite. The interpenetrating composite microstructure with ceramic and epoxy gave a flexural strength increase of 45.65 MPa compared to the ceramic. Unfortunately, the infiltration procedure of aramid-epoxy reinforcement did not realise the full tensile strength potential of aramid fibres.
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GIANCHANDANI, PARDEEP KUMAR. "Joining of Ceramics and Ceramic Matrix Composites (CMC) for Aerospace and Energy Applications." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2711092.
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SiC-based ceramics and composites (SiC, C/SiC & SiC/SiC) are more and more extensively used as advanced materials for aerospace and energy applications. Existing applications are expanding continuously and require advanced materials, design and joining technologies.
The objective of this thesis was to join SiC-based ceramic matrix composites (CMC), ceramics (SiC, Mullite, Alumina) and SiC-based ceramic foams for aerospace and energy applications.
The research was aimed to develop strong, oxidation resistant and high temperature stable joints.
A novel joining technique defined “RM-Wrap” (RM=Mo, Nb, Ta, W Refractory Metals) has been developed within this thesis. The developed technique is a novel brazing technology named RM-Wrap after the metal used as a wrap to contain one or more silicon foils (e.g. Mo-Wrap when a Mo wrap is used to contain a Si foil).
It is a pressure-less joining technology performed at 1450 oC, under an inert environment (Argon flow).
Joining materials are in-situ formed composites made of refractory metals silicides (MoSi2, NbSi2, TaSi2 and WSi2) embedded in a silicon matrix.
RM-Wrap is a highly tailorable joining technique: the quantity of each phase can be modified and more than one refractory metals can be used together. RM-Wrap has been very effective in joining both coated and uncoated CMC, porous and non-porous materials: ceramics (oxide and non-oxide), CMC (SiC-based) and highly porous substrates (SiC foams) having porosity higher than 80% have been soundly joined.
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The joint morphology (interphase and interface) and elemental composition of the joining material was investigated in detail using FESEM and EDS which showed uniform, continuous and crack free joints. XRD investigation confirms the formation of metal silicides. Oxidation resistance of joints was carried out at 1100 oC for 30 minutes (for CMC joints) and 6 hours (for monolithic ceramic joints) in the air; prior and post oxidation examination of joint morphology showed no morphological change and joints remained firmly joined.
Sandwich structures have been developed by Mo-wrap joining two C/SiC as “skins” to the “core” SiC foam. Sandwich structures were tested for thermal shock resistance from RT to 1100 oC in the air for 2 minutes. Three cycles on a single sandwich structure were performed, which remained joined and the joining material composition unchanged.
Joints were mechanically tested in three different modes (i) compression, (ii) tensile and (iii) torsion. Joint strength was higher than the interlaminar shear strength of composites as the fracture was always observed in composites.
In case of monolithic ceramic (SiC) a mixed failure (cohesive and adhesive) was found, which suggest that the joint strength is comparable to ceramic one.
Micro- and nanoindentation tests were also carried out on joining materials.
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Kister, Guillaume. "Ceramic-matrix composites for gas turbine applications." Thesis, University of Bath, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299850.
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Whitney, Michael J. (Michael John). "Transformation-mismatch plasticity in zirconia ceramic composites." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43447.
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Pemberton, Sonya Rachel. "Toughening ceramics : optimising the fracture behaviour of metallic fibre reinforced ceramic matrix composites (MFCs)." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607820.
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Shin, Hyunho. "Interface reactions and their influence on properties of SiC fiber-reinforced ceramic matrix composites." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19122.
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Villalobos, Guillermo Roberts. "Strength enhancement of nicalon reinforced lithium aluminosilicate containing a Ta₂O₅ second phase." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19969.
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Stackpoole, Margaret Mary. "Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10564.
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Texier, Anne. "The fabrication of carbon-fiber composites by aqueous suspension prepregging with larc-tpi and peek." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020638/.
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UHLMANN, FRANZISKA JOHANNA LUISE. "Protective Ultra-High Temperature Coatings/ Ceramics (UHTCs) for Ceramic Matrix Composites in Extreme Environments." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2644372.
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This thesis is focused on the development of a protective coating system for Cf/SiC SiCARBONTM (Airbus trademark) materials against very high temperatures in extreme environment. Here, we concentrate on the application of this technology in combustion chambers, for example in orbital thrusters. During combustion, the composite material needs to be protected against oxidation caused by the extreme conditions. With the aim to increase the combustion performance using higher temperatures (up to 1850 °C), this thesis deals with the replacement of the current Environmental Barrier Coating (EBC) solution (CVD-SiC coating, Chemical Vapor Deposition) by an Ultra High Temperature Ceramic (UHTC) based coating system. Different challenges of this approach are, for instance, the CTE mismatch between Cf/SiC and UHTC materials and the feasibility to create a dense, thick and adherent UHTC based coating on the hot gas wall (inner wall) of a small combustion chamber.
In this work, a suitable coating process (High Performance Plasma Coating process, HPPC) for inner wall coatings is selected and further developed to create ZrB2 based coatings on Cf/SiC based substrate materials. Based on a parameter study, the coating quality of HPPC based ZrB2 coatings is optimized depending on plasma current, chamber pressure, powder flow rate, preheating and cooling rate. HPPC coatings with different material combinations (ZrB2, ZrB2-SiC, ZrB2-TaC, ZrB2-LaB6) are investigated regarding coating adhesion, voids, composition and thermo-chemical behavior within a combustion chamber-like environment.
To decrease the CTE mismatch between Cf/SiC substrate and a ZrB2 based coating and to increase the thermo-chemical resistance of the composite, the SiC matrix material is modified by ZrB2 and Ta additions. Cf/SiC-ZrB2-TaC composites with different SiC/ZrB2-TaC ratios are fabricated and investigated regarding microstructure, chemical composition and material properties (physical, thermo-physical, mechanical and thermo-chemical). The adhesion of HPPC based ZrB2 coatings on Cf/SiC composites is enhanced by a ZrB2 and TaC matrix modification.
Based on the results, interactions between process parameters, coating composition and substrate material are analyzed and provide the base for ZrB2 based EBCs of the inner wall coatings on Cf/SiC based components. By means of the obtained findings, the potential of several material systems is derived in order to develop a protective coating for long-term applications in combustion chamber environments.
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Bulsara, Vatsal N. "Effects of fiber spatial distribution and interphase on transverse damage in fiber-reinforced ceramic matrix composites." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/21429.
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Kokan, Julie Runyan. "Microstructure/electrical property correlations in ceramic matrix composites." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19594.
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Basaran, Yanki. "Studies On The Development Of Magnetoelectric Ceramic Composites." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609612/index.pdf.
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The aim of this thesis work was to develop magnetoelectric (ME) composites consisting of piezoelectric and magnetostrictive components. The piezoelectric constituent was selected as a PZT ceramic modified by strontium, bismuth and manganese. The magnetostrictive phase was nickel ferrite (NF) ceramic doped by cobalt, copper and manganese. The properties of component phases were optimized in order to enhance the ME effect in the composite.
In the first part of the thesis, effects of sintering temperature on the dielectric and piezoelectric properties of PZT and on the electrical and magnetic properties of NF ceramics were investigated in the temperature range covered from 1150 to 1250 °C. The best piezoelectric properties in PZT were attained at 1250 °
C. At this sintering temperature, values of piezoelectric strain coefficient, dielectric constant, and electromechanical coupling coefficient were 434 pC/N, 1320 and 0.48, respectively. NF ceramics showed poor densification
80 %TD was attained at 1250 °
C. In order to obtain higher densities in ferrites, Bi2O3 was used as a sintering aid. Addition of Bi2O3 enhanced densification up to 97 %TD, and improved electrical and magnetic properties of ferrites. Highest DC-resistivity of 1.15*10^8 ohm-cm and highest magnetostriction of ~26 ppm were attained in NF ceramics doped with 1 wt% Bi2O3. In the second part of the thesis, ME composites were manufactured either as bulk composites or as laminated composites. The efficiency of different composite types was evaluated in terms of voltage output in response to the applied magnetic field. Higher outputs were observed in laminated composites.
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Lee, Woo Young. "Chemical vapor deposition of dispersed phase ceramic composites." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11857.
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Saewong, Pakamard. "Erosion of glass and glass-ceramic matrix composites." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300838.
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Daniel, Adrian Matthew. "Interfacial properties of fibre reinforced ceramic matrix composites." Thesis, University of Warwick, 1994. http://wrap.warwick.ac.uk/56665/.
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A review of ceramic matrix composites development over the past thirty years is presented, with emphasis placed on their application in gas turbine engine components. The fracture mechanics of brittle solids are outlined and the toughening mechanisms operating within continuous fibre reinforced ceramic matrix composites are discussed. The importance of the fibre-matrix interface in governing the overall mechanical properties of a composite is highlighted with respect to the micromechanical properties of interface debond fracture surface energy OJ and frictional shear stress t. Current techniques for measuring OJ and t are listed, together with their inherent disadvantages. The requirement for a micro-indentation system that can be used to measure interfacial properties via individual fibre pushing experiments across a wide range of composite systems, is discussed. The development of a unique Scanning Electron Microscope (SEM) based microindentation system is described in detail. It enables dynamic, high magnification imaging of the indentor tip and specimen contact point, and continuously records applied load and tip displacement throughout the indentation cycle. A piezoelectric load cell, coupled to a specifically developed amplifier, enables load resolution of 2mN measured up to the maximum possible of 20N. Novel capacitance displacement gauge design gives a resolution of lOnm over a l00pm range. The instrument has been used successfully to measure the interface micromechanical properties across a wide range of silicon carbide fibre reinforced glass and glass ceramic matrix composites. This data has been correlated with interface structural information obtained via Transmission Electron Microscopy (TEM) and SEM. Effects of oxidation, fatigue testing and interface pre-synthesis via fibre coating, have been measured. Fibres with diameters ranging from 7JJ;mto 150pm have been tested to demonstrate the versatility of the device for interfacial property measurement across the full range of modem ceramic matrix composites. Successful attempts have been made to correlate changes in the interfacial OJ and t to changes in overall composite mechanical behaviour. Theoretical requirements for values of G, that introduce toughness to composites have been discussed and compared to those determined by experiment. Variation of t and its effect on matrix micro-cracking and the tough!brittle property transition of a composite has been measured. Other applications that exploit the instrument's high resolution and imaging capability have been demonstrated. They include hardness and modulus measurement of individual phases in heterogeneous materials, and direct observation of controlled crack growth in ceramic composites. Ideas for the development of the instrument into a more versatile SEM based mechanical test facility are proposed.
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Jones, Alan Hywel. "Synthesis and tribology of Sialon/TiB2 ceramic composites." Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/56017/.
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The inclusion of TiB2 particles in a Si3N4 or sialon matrix has the potential to improve the materials properties over those of the Si3N4 alone. The combination of the excellent properties of sialon and the high hardness of the TiB2 makes these materials potentially suitable for tribological applications. This research has investigated the use of chemical reactions that can take place during sintering to synthesise TiB2 from TiN and BN. The reactions not only produce TiB2 but simultaneously synthesise the matrix material. The sialon matrix is used as a flexible receptor for excess nitrogen and oxygen. Using such reactions, sialonlTiB 2 composites were successfully produced by both hot pressing and pressureless sintering. It was shown that these materials achieve densities close to the theoretical and contain only the required phases of TiB2 and ~ sialon. Pressureless sintered materials also contain residual sintering aid as an intergranular phase. The composites wee characterised with respect to their microstructure, hardness, fracture toughness and tribological properties. A specially designed wear test apparatus was constructed for the tribological testing. The pin-on-disc apparatus was capable of testing the small volumes of material (minimum diameter of disc ~ 15mm) typically produced at the development stage. The materials were found to have high hardness and reasonable fracture toughness which was attributed primarily to the properties of the matrix phase with some possible toughening from the presence of TiB 2 . Tribological testing revealed high dry sliding coefficients of friction (Jl) for the composites sliding on themselves and reasonable values for the wear coefficient (k) were measured. Wear was found to be dominated by tribochemical reactions forming tribofilms which act to reduce wear of the disc. However, the presence of TiB2 was not seen to contribute directly to the tribological properties of these materials and the usefulness of this type of composite is questioned.
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Tuan, W. H. "Sintering stresses and the fabrication of ceramic composites." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383801.
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Pisitpaibool, Chandech. "Wear behaviour of ceramic particle reinforced ferrous composites." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369937.
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Moffatt, James E. "High temperature crack growth of advanced ceramic composites." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409861.
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Ren, Guogang. "Fibre reinforced ceramic moulding composites manufacture and characterisation." Thesis, Queen Mary, University of London, 1999. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1710.
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Ceramic materials have considerable attraction for use in applications where the service temperatures are high and where fire performance and non-combustibility are important. Unfortunately most monolithic ceramic materials are extremely brittle which limits their use for structural applications. The development of fibre and particulate reinforced ceramic composites provides a route to achieving increased toughness in the materials, although this is often at the expense of ultimate strengths and/or the process-ability of the materials. Many reinforcing fibres used with ceramics are inherently expensive and manufacturing routes to produce fibre reinforced materials can involve high processing temperatures and are consequently expensive. A key goal of this research therefore is to develop a new type of ceramic matrix composites that combine toughness, strength and process-ability to provide a cost effective structural material. The research described in this thesis has been concerned with the development and characterisation of a series of ceramic compounds that can be moulded at modest temperatures( 130-160" C) and pressures in a manufacturing system that replicates dough moulding compounds (DMC) as used for polymeric matrix composites. The conventional polyester matrix of polymeric DMC has been replaced by a soluble inorganic system which is compounded with fibres, fillers and hardening agents to produce a paste-like or doughy substance The handle-ability of the material is determined by the viscosity of the matrix and the type or amount of fillers and additives present. The research has involved a careful set of experiments in which the formulation of the ceramic DMC has been systematically varied in order to achieve an optimum viscosity for storage and handling together with a further series of experiments studying the hardening and cure of the compounds. The mechanical properties of the compounds have been measured and additional formulation changes have been introduced to maintain desirable processing characteristics while improving mechanical properties, and in particular the impact resistance using instrumented falling weight impact machines. Finally the fire properties of the compounds have been studied using cone calorimetry and indicative furnace testing. The structure of the compound has been studied throughout the programme with various microscopic techniques and thermal analysis systems used to characterise the materials, their dispersion and changes that occurred during processing and after high temperature exposure. The final result of the programme has been the identification of a range of material formulations that can provide a tough moulding compound, capable of high temperature service use, that possesses useful structural properties and which can be processed cheaply at modest temperatures using low cost materials.
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Markaki, Athina Emmanuel. "Mechanical behaviour of layered metal foam/ceramic composites." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621791.
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Liu, Jing. "Processing and properties of metal-ceramic interpenetrating composites." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9465.
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Composite materials consisting of two or more different phases are very extensively used in modern society. If the composite is designed and fabricated correctly, then desirable properties not available in any single conventional material can be achieved. Ceramic reinforced aluminium alloys are desired for high performance applications due to their superior properties compared with the soft, unreinforced metal. However "traditional" particle or fibre reinforced composites suffer from a limited ability to achieve high reinforcement levels. Interpenetrating composites (IPCs) have 3-3 connectivity, with both the matrix and reinforcement phases being fully connected; they are expected to provide truly multifunctional properties. Whilst pressure is normally needed for the processing of IPCs due to the poor wetting between most aluminium alloys and ceramic materials, it raises the risk of ceramic preform damage and limits the component shape. In this research, interpenetrating composites were produced at atmospheric pressure by infiltrating 10 wt% magnesium content Al-Mg alloys into 15-40% dense, gel-cast ceramic foams with average cell sizes from 100 to 500 μm, made from three different ceramics. Previous research at Loughborough University focused on the aluminium / alumina system. In this study, the ceramic foams were made from spinel, mullite and silicon carbide. Effects of processing parameters, including atmosphere, temperature and time, were investigated. The results showed that heating the metal-ceramic couple in Ar and infiltrating in N2 followed by cooling in Ar was a better approach for the infiltration process than heating in N2 during the whole process. The Al(Mg)/spinel system was observed to require the lowest processing temperature and shortest time compared with the Al(Mg)/mullite and Al(Mg)/alumina systems. Microstructures of IPCs were characterised using a series of techniques, including optical microscopy, field emission gun scanning electron microscopy (FEG SEM), X-ray diffraction (XRD), dual beam focused ion beam (DBFIB) and transmission electron microscopy (TEM). A continuous nitride layer consisting of AlN and Mg3N2 was observed at the metal-ceramic interface of the spinel and mullite-based IPCs ABSTRACT ii with MgO and MgAl2O4 observed at localised positions, similar to alumina-based composites. Based on these results, a two-step nitridation infiltration mechanism has been proposed for oxide ceramic foam / aluminium-magnesium IPCs. The infiltration is believed to be dependent on the reaction between Mg and N2 to form Mg3N2, which then deposits onto the oxide ceramic foam surface; once in contact with molten Al, Mg3N2 reacts with the Al to form AlN, which is wetted by the liquid aluminium and induced the infiltration. In the case of mullite-based composites, a small amount of Mg2Si was observed as a result of the reactions between the SiO2 phase in the mullite foam and the liquid metal. The feasibility of fabricating SiC foam / Al-Mg and SiC foam / Al-Si IPCs by pressureless infiltration of molten Al alloys into gel-cast SiC foams has been also evaluated in this research. Serious degradation of the SiC foam was observed in the SiC / Al-Mg IPCs, resulting in the formation of Mg2Si and Al4C3, whilst the SiC foam could not be spontaneously infiltrated by the Al-Si alloy without the presence of Mg. A modified pressureless infiltration technique was developed to allow the manufacture of fully infiltrated SiC foam / Al-Si interpenetrating composites, with little degradation of the SiC foam and very little formation of detrimental phases. Preliminary property characterisation showed that the ceramic-foam based IPCs were up to twice as wear resistant as composites made by infiltrating a bed of ceramic powder. Effects of parameters on wear resistance have been investigated, including the ceramic material, foam density, cell size and degree of sintering. The denser the ceramic foam, the stronger the foam struts, and hence the more effective the composites were in resisting wear. However, a non-linear relationship between the foam cell size and the wear rate was observed; the composites with moderate mean foam cell sizes exhibited better properties than composites with smaller or larger cell sizes. Thermal expansion behaviour of the IPCs has been also studied; a clear hysteresis was observed in the strain curve between heating and cooling. The coefficient of thermal expansion (CTE) was observed to vary as a function of temperature.
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Parham, Hamed. "Ceramic-carbon nanotube composites and their potential applications." Thesis, University of Exeter, 2012. http://hdl.handle.net/10871/8141.
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Carbon nanotubes (CNTs) have been the subject of intensive research for nearly two decades, and this is due to their exceptional lightness, large aspect ratio, extraordinary mechanical, electrical, thermal properties and additional multi-functional characteristics. Ceramics have high stiffness and good thermal stability with a relatively low density, and they are an important constituent in the fabrication of advanced composites where high thermal and chemical stability are important. However, brittleness has limited their application in many structural applications. The combination of ceramic (alumina in particular) and CNTs, endeavouring to develop functional composites, offers a very attractive system for research and development. The fabrication of such alumina-CNT composites at bulk scale is therefore highly desirable for industrial applications. However, the synthesis of such composites possesses many technical challenges which need to be addressed. Poor synergy between the matrix and CNTs, potential damage to CNTs, obtaining a uniform and agglomeration-free distribution of CNTs within the matrix, and high cost of CNTs and processes involved in their composite fabrication have proved to be the significant challenges. In this thesis, the focuses are laid on addressing these issues and on the fabrication of specially engineered composites for particular applications such as filter and composites with improved mechanical properties. In this regard, it has been tried to directly fabricate CNTs in different ceramic matrices based on the application requirements. After that, the critical issues and challenges in the fabrication of these functional materials have been clearly investigated and by introducing novel methods and approaches, it has been tried to solve these problems. Also, a new polymer-ceramic-CNT composite has been fabricated by using two different thermoset (epoxy resin) and thermoplastic (polyamide 12) matrices. In this regard, good interfacial bonding between the composite elements along with good wettability of ceramic and CNTs with polymer had to be addressed as critical issues and challenges in the fabrication process. If the adherence at the interface is not strong enough, the material will tear and fail easier. In contrary, a tailored functionalization of CNTs can lead to an improved wettability and as the results, strong interfacial adhesion and bonding between the composite elements. These dominating factors will improve the degree of filling which results in existence of fewer voids inside the composite. These voids will act later as stress points and reduce the composite strength. At the end, the mechanical properties of the fabricated samples have been assessed. The CNT filters have been tested in the removal of bioorganic (yeast cells) and inorganic (heavy metal ions) contaminants from water, and of particulates from air, and they all showed very promising results. More than 99.6% of the air particles (size ranges from 0.3 to 10 µm) were filtered using 300 mm long CNT filter. A complete removal of heavy metal ions from water was reported particularly for single ion. 98% of the yeast cells were filtered. Different factors involved in the filtration efficiency such as ceramic pore size, length of filters, CNT loading and injection rates have also been discussed. Furthermore, the mechanical properties (compression test, hardness and impact test) of the composite materials (including ceramic-CNT, epoxy resin-ceramic-CNT and polyamide-ceramic-CNT composites) have been assessed. During impact test, the epoxy resin-ceramic-CNT composite absorbed 117.2% and 32.7% more energy compared to the pure epoxy resin and epoxy resin-ceramic composite, respectively. The epoxy resin-ceramic-CNT composite sustained 40% more elastic deformation before breakage compared to the epoxy resin-ceramic composite as a result of the CNT reinforcement. The addition of CNTs to the polyamide12-ceramic composite increased its yield stress by 41%. All of these results represent a big leap towards practical applications for the composite reported in the thesis, which may open up new opportunities for CNT engineering at industrial scales, due to the easy fabrication methods introduced and the promising performance they have exhibited.
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Evarts, Jonathan S. "Advanced Processing Techniques For Co-Continuous Ceramic Composites." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218218162.
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Namboodri, Shannon Leahy. "Processing and characterization of ceramic superconductor/polymer composites." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163834/.
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Walter, Mark E. Knowles James K. Knowles James K. "The evolution of damage in ceramic matrix composites /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-01072008-112449.
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Shan, Xiaobing Cheng Zhongyang. "High dielectric constant 0-3 ceramic-polymer composites." Auburn, Ala, 2009. http://hdl.handle.net/10415/1820.
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Kasichainula, Sridhar. "Multilayered ceramic/metal composites by extrusion freeform fabrication." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/280308.
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Metal layers within a laminar ceramic can improve damage tolerance of ceramics by arresting large cracks either by ductile bridging or by crack deflection at the ceramic/metal interface, which will allow engineers to design reliable ceramics for structural applications. At low volume fractions of the metal ductile bridging is not very effective, mainly owing to decreased distance between the crack tip and next ceramic layer. Significant increase in the energy absorption during fracture can come from delamination, but depends on the interfacial fracture resistance. A two-fold increase in energy absorption is realized in the case of glass-ceramic/silver laminates prepared by extrusion freeform fabrication. Interfacial fracture energy for glass-ceramic/silver is found to be 100 J/m² in comparison to 15 J/m² for glass-ceramic/SiC, which should explain the sporadic crack deflection in notched four-point bend. For a short beam flexural test shear failure is more favorable in four-point than in three-point bending. In four-point tests, the shear stresses between the outer and inner loading pins can precipitate shear delamination prior to tensile cracking of the layers. Damage modes under low velocity impact tests are similar to four-point bend showing delamination as primary energy dissipation mechanism.
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Silva, João Gustavo Pereira da. "Modeling of load transfer in ceramic matrix composites." Florianópolis, SC, 2011. http://repositorio.ufsc.br/xmlui/handle/123456789/95298.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2011Made available in DSpace on 2012-10-25T23:51:25Z (GMT). No. of bitstreams: 1 296281.pdf: 1910722 bytes, checksum: 8f6cef994039f41950823b885f52d26e (MD5)
Este trabalho se dedica a apresentar alguns modelos de transferência de carga entre uma matriz porosa e fibras em compósitos de matriz cerâmica. Um modelo analítico para a transferência de carga em fibras curtas é desenvolvido, baseado em modelos já existentes para compósitos poliméricos. Além disso, a geometria e a resistência das fibras, juntamente com a porosidade da matriz são incluídas na presente análise. As curvas teóricas para as tensões longitudinais e de cisalhamento ao longo da interface fibra-matriz são apresentadas. Elas alcançam um máximo no meio das fibras curtas. Torna-se evidente que o comprimento crítico é governado pelo conjunto de propriedades da fibra e da matriz, que influenciam a capacidade de transferência de carga nos compósitos. Adicionalmente, a solução simplificada apresentada facilita o entendimento dos mecanismos interfaciais se utilizando de uma matriz porosa. Outro foco do trabalho é um algoritmo que simula o teste de feixes contínuos de fibras cerâmicas usando-se métodos de Monte Carlo. É mostrado que a resistência do feixe é sempre menor que a resistência média das fibras testadas individualmente. Tal comportamento é explicado por modelos de transferência de carga. Neste trabalho, diferentes modelos de transferência de carga foram implementados em uma simulação de um ensaio de tração em feixes de fibras. Os resultados estão de acordo com os experimentos de fibra simples e feixe realizados e constituem uma ferramenta útil para o projeto de materiais reforçados com fibras cerâmicas.
The aim of this work is to present some models of load transfer between porous matrix and fibers in ceramic matrix composites. An analytical model for short fibers is developed, based on the earlier shear-lag models used for polymeric composites. Moreover, geometry and strength of fibers in addition to the matrix porosity are included in the present analysis. The theoretical curves for the longitudinal and shear stress distribution along the fiber-porous matrix interface are presented. They exhibited a maximum strength point at the middle of the short fibers. It became evident that the critical length is governed by the relative properties of the fibers, matrix and porosity, which greatly influenced the load carrying capacity of the fibers in the composites. In addition, the present simplified solution facilitates the understanding of the interface mechanism using porous matrix. In addition, a bundle testing routine is implemented using Monte Carlo methods. It is common knowledge that for bundles of fibers in composites, that the bundle strength is always less than the sum of the fiber strengths. This behavior can be explained by load-sharing models. At this work, different load sharing models were implemented on a simulated tensile test of ceramic oxide fibers. The results are in agreement with the experimental results of single-fiber and bundle testing and constitute a useful tool for the design of fiber-reinforced materials.
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Peng, Fei. "Pressureless sintering and oxidation resistance of zrb2 based ceramic composites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28208.
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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Robert F. Speyer; Committee Member: George Kardomateas; Committee Member: Preet Singh; Committee Member: Robert L. Snyder; Committee Member: Thomas H. Sanders, Jr.