CQ - 9th International Conference
Advanced Inorganic Fibre Composites for Structural and Thermal Management Applications
ABSTRACTS
CQ-1:IL01 Development of Oxide Ceramic Fibers for OCMCs
B. Clauß, S. Pfeifer, H.-J. Bauder, S. Kröner, H. Stolpmann, C. GRELLER, A. Renfftlen, L. REINDERS, M. Caliskan, M.R. Buchmeiser, German Institutes of Textile and Fiber Research DITF, Denkendorf, Germany
Oxide fiber research and development began 30 years ago at the German Institutes of Textile and Fiber Research (DITF) in Denkendorf, Germany. During this time, basic and applied research was conducted to achieve high-quality oxide fibers based on aluminum oxide and mullite. This goal has been achieved and the presentation will give an overview of the state of the art and current developments in our so-called OxCeFi fibers. Over the last years, the DITF have built up a complete pilot line for fiber production, which includes all steps from spinning mass production to dry spinning, calcination and sintering. The line was designed to produce fiber quantities large enough to be tested in ceramic matrix composites (OCMC) and used for further developments. A high-end jacquard weaving technology has also been established at the institutes and fabrics made of OxCeFi fibers are successfully produced. Further developments at the DITF focus on doped oxide fibers and fibers with dispersion structures with the aim of reducing grain growth, increasing creep stability and enhancing textile processability.
CQ-1:IL02 Which is the Best SiC Precursor for Chemical Vapor Infiltration and High Temperature Applications?
A. Desenfant1, G. Laduye2, S. Goujard3, G. Vignoles1, G. Chollon1, 1Laboratoire des Composites Thermostructuraux, CNRS, Pessac, France; 2Air Liquide, France; 3Safran Ceramics, France
Silicon carbide (SiC) is a material of choice for high temperatures structural applications, for instance as protective coating or as the matrix of ceramic matrix composites. CH3SiCl3/H2 mixtures have been used for decades as gas precursor for the synthesis of SiC coatings by chemical vapor deposition/infiltration (CVD-CVI). Only a few specific experimental conditions are favorable to pure crystalline SiC and homogeneous thicknesses. Furthermore, small variations in temperature or residence time can alter the local gas composition and thus the stoichiometry and microstructure of the coating. This work reviews the investigation of various alternative gas precursors, either as a single molecule or with two separate C and Si precursors, and operated in a wide range of experimental conditions. The final aim is to improve the robustness of the CVD/CVI process in terms of coating stoichiometry and infiltration and, more widely, to better understand the CVD of SiC. The approach is multi-experimental and based on FTIR gas analysis, deposition kinetic measurements, elemental and structure analyses, and model pore infiltration. Thermochemical and kinetic simulations of the gas-phase were also performed that allowed proposing a mechanism for the decomposition of the precursors.
CQ-1:L04 Upscaling of Spinning Processes for Endless Multifilament Ceramic Fibers
A. Rüdinger, R. Herborn, H. Scholz, P. Vierhaus, J. Vetter; Fraunhofer ISC, Center for High Temperature Materials and Design HTL, Bayreuth, Würzburg, Germany
In the last decades, Fraunhofer ISC worked on the development of ceramic reinforcing fibers. Starting from the lab scale, oxidic fibers, e.g. alumina or mullite fibers were developed based on the sol-gel process and non-oxidic fibers, e.g. SiC or Si-B-N-C were manufactured from metal-organic precursors. These processes have been scaled up to technical scale enabling a fiber production of several kg/year. E.g., for aqueous precursors in the system Al2O3 – SiO2, the entire process route from spinning dope preparation to an endless sintering process was developed. With non-oxidic fibers, Fraunhofer ISC developed together with several partners in Germany a fiber in the system Si-B-N-C, a so-called SiC fiber of the fourth generation. The fiber process has been up-scaled to a level of 500 filaments and 200 m of endless multifilament. Since 2017, Fraunhofer-Center HTL builds a fiber pilot plant for the manufacture of ceramic fibers on a larger scale. The capacity of the ceramic fiber lines – one for non-oxide and one for oxide fibers - together will be approx. . 5 - 10 t/year of 500 – 1000 filament endless rovings. The start of operation of both lines is planned for 2021. The current work addresses the buildup of the new fiber lines and the transfer of the fiber spinning process.
CQ-2:IL01 Oxide Fiber Coatings for Lifetime Extension of SiC/SiC Ceramic-matrix Composites
M.K. Cinibulk1, E.E. Boakye1, 2, P. Mogilevsky1, 2, R.S. Hay1, 1Air Force Research Laboratory, WPAFB, OH, USA; 2UES, Inc., Dayton, OH, USA
Two of the highest capability priorities for the U.S. Air Force, energy-efficient turbine engines and long-range precision strike require high-temperature ceramic-matrix composites (CMCs) to enable increased turbine engine efficiency and thermal protection of high-speed aero-structures. However, SiC/SiC CMCs are not only susceptible to oxidation, but the silica oxidation product volatilizes in the presence of water in the combustion environment. While external environmental barrier coatings (EBCs) have been engineered to minimize these issues, durability is limited if the EBC is breached at intermediate-temperatures where oxidation of boron nitride precedes oxidation of SiC, inhibiting internal sealing mechanisms from functioning. Furthermore, at the very high temperatures where SiC/SiC CMCs are being considered for application (~1500°C), BN oxidation kinetics are not well known and any ingress of combustion gases will likely lead to rapid loss of BN. The use of an oxide fiber coating should offer a substantial increase in resistance to oxidation embrittlement. This presentation will review work in our laboratory on the development of rare-earth disilicate fiber coatings and interphases for SiC/SiC CMCs and evaluating their thermomechanical behavior.
CQ-2:IL02 Tailoring of CMC Properties by Varying Fiber Matrix Interfaces
J. Moosburger-Will, D. KOCH, S. HORN, Institute of Materials Resource Management, University of Augsburg, Augsburg, Germany
The mechanical properties of ceramic matrix composites (CMC), e.g., their damage tolerant fracture behavior, sensitively depend on the fiber matrix interfacial properties. The fiber matrix interaction mainly is determined by the surface properties of the fibers. These can be varied e.g., by oxidative processes, sizing, or coating. To investigate the interaction between fibers and matrix, the micromechanical single fiber push-out test represents a powerful tool. An indenter-tip axially loads an individual fiber, oriented perpendicular to the surface of a thin composite sample. This induces fiber matrix debonding and fiber push-out. Evaluation of the load-displacement curve allows extraction of interfacial parameters. The characterization of the fiber surface is performed e.g., by spectroscopy or microscopy. Single fiber push-out testing of carbon fiber reinforced phenolic resin, which represents the intermediate material for C/C-SiC production, revealed a clear influence of the fiber surface treatment on the interfacial fracture toughness. The trends found by micromechanical testing of the reinforced polymer agree with results from macroscopic testing of the corresponding C/C-SiC. We show that adaption of the fiber matrix interaction promises a defined tailoring of CMC properties.
CQ-2:IL03 Integration of Silicon-based Materials to Metals for Thermostructural and Thermal Management Applications
R. Asthana1, M. Singh2, J. Martinez Fernandez3, F.M. Valera3, 1University of Wisconsin-Stout, Menomonie, WI, USA; 2Ohio Aerospace Institute, Cleveland, OH, USA; 3Depto Física de la Materia Condensada-ICMSE, Universidad de Sevilla, Spain
Silicon nitride/ INCONEL-625 joints were vacuum brazed using Cu-ABA (Cu-3Si-2Al-2.25Ti, wt%, TL: 1297 K) braze alloy in conjunction with refractory metal (W, Mo and Ta) interlayers to manage thermal stresses and reduce the strain energy. The following interlayer arrangements were used: Si3N4/Cu-ABA/W/Cu-ABA/Mo/Cu-ABA/INCONEL-625 and Si3N4/ Cu-ABA/W/ Cu-ABA /Ta/Cu-ABA/ INCONEL-625. The brazed joints were characterized for microstructure and microhardness using SEM, EDS, TEM and Knoop test. High-resolution SEM and TEM examination was conducted at each of the following joint interfaces: Si3N4-Cu ABA, Cu ABA-Mo, Cu ABA-W, Cu ABA-INCONEL-625 for the Si3N4/W/Mo/INCONEL-625 joints and Si3N4-Cu ABA, Cu ABA-W, Cu ABA-Ta and Cu ABA- INCONEL-625 for the Si3N4/W/Ta/INCONEL-625 joints. Well-bonded interfaces formed in both types of joints with the microhardness profiles in joints mimicking the interlayer arrangement. Preliminary mechanical tests revealed improved shear strength in joints made using the interlayers relative to directly brazed Si3N4/INCONEL-625 joints. Observations on elemental distribution, interphase formation, dislocation substructure and thermal behavior of the joints will be presented.
CQ-2:L04 Evaluation of Fiber Interphase Coatings by Tensile Testing of Fiber Bundles and Minicomposites
J. Maier, A. Nöth, Fraunhofer ISC/Center for High Temperature Materials and Design HTL, Würzburg, Germany
In the present work, fiber interphase coatings were developed for the use in SiC/SiC ceramic matrix composites (CMCs). BN/SiC- and BN/Si3N4-bilayer coatings were applied on SiC fibers by a continuous wet-chemical dip-coating process. We show the optimization of the coating process to achieve homogeneous interphase coatings without significant bridging. Coated and uncoated fiber bundles were tested by tensile tests at room temperature and at high temperatures using a new type of measuring furnace. The force-displacement curves were used to determine the Weibull modulus and the corresponding scale parameter for fiber elongation and fiber strength. We discuss the influence of the fiber coatings on these properties in comparison to the properties of the uncoated fiber bundles. Furthermore, we present the influence of the coating on the modulus of elasticity and the strength of a fiber bundle. SiC/SiC minicomposites were fabricated by chemical vapor infiltration of coated and uncoated single fiber bundles. The results on tensile testing of the minicomposites are presented. We discuss the influence of the fiber interphase coating system on the stress-strain curve of the minicomposites and draw conclusions on the interphase design for damage-tolerant SiC/SiC CMCs.
CQ-3:IL01 A New Route to Processing CMCs with Controlled and Variable Matrix Composition
J. Binner, B. Baker, V. Rubio*, University of Birmingham, Birminghan, UK; *Now with the National Composite Centre, Bristol, UK
Continuous fibre ceramic matrix composites are a promising class of materials for application in demanding environments. The specific application in which a particular component is to be employed defines the required properties it needs to possess, which will in turn influence properties such as the density, composition and directionality of the fibre reinforcement and composition of the matrix. Whilst most of the time there is interest in producing composites from the stacking of fibre sheets and having a uniform and homogeneous matrix, there are also times when having a more flexible approach to achieve dense composites, potentially based on 3D preforms, and with locally varying matrix composition would be preferred. This paper describes a very versatile method for producing high quality CMCs through slurry processing with no limitations on size and the ability to vary the deposition of the matrix as desired, including varying the local composition and/or particle size. The mechanical and thermoablative properties of UHTCMCs produced via this approach are compared to those produced conventionally and the scope of the method for producing functionally graded materials is discussed.
CQ-3:IL03 Scaling up of MW-CVI Technology for the Production of CVI SiC-based Ceramic Matrix Composites
R. D'Ambrosio, L. Aliotta, V. Gigante, A. Lazzeri, University of Pisa, Dipartimento di Ingegneria Chimica e Industriale, Pisa, Italy
Silicon carbide based (SiC) Ceramic Matrix Composites (CMCs) evoked much industrial consideration for thermally loaded components due to their attractive high temperature properties, such as creep resistance and microstructural stability. Up to now their use is limited only to high end applications because of their extremely high cost so new and more efficient manufacturing technologies are needed in order to reduce production costs and expand their use. An innovative hybrid Microwave assisted Chemical Vapor Infiltration (MW-CVI) pilot plant to produce SiC-based CMCs was designed, built and setup, as a part of the European project HELM. Different from existing lab-scale equipment, the design of this pilot plant was carried out with the idea of a further industrial scale-up. In order to tailor a suitable temperature profile of pilot-scale preforms, the inner chamber of the reactor and all the components exposed to high temperature and extreme chemical environment were built in conductive graphite, acting as an overmoded resonant cavity at the frequencies of interest. The design as well as the study of the reactor was supported by means of a rigorous numerical modelling based on Comsol Multiphysics software to determine homogeneous heating conditions and power requirements.
CQ-3:IL04 Insights in the Infiltration of Molten Silicon in Porous Preforms
J. Roger, Univ. Bordeaux, CNRS, CEA, Safran Ceramics, LCTS, UMR 5801, Pessac, France
Liquid silicon infiltration (LSI) is a promising manufacturing process for the production of SiC-based-matrix composites intended for hot parts of engine structures. Two main processes involving the infiltration of molten silicon were examined. The first way consists of infiltrating molten silicon into SiC preforms, which is considered as non-reactive since SiC and silicon are in equilibrium. The second way implies a reaction to synthesize SiC. In this case, the obtained matrix should be ideally composed of pure SiC or alternatively, it could also contain another refractory ceramic phase. However, each method involves scientific challenges to be examined closely in order to successfully overcome them. We studied the infiltration of molten silicon in more or less complex porous SiC materials for a better understanding of the mechanisms and to determine their kinetics. The reactive infiltration of molten silicon was also considered in two cases: in pure carbon preforms and in TiC-SiC preforms. The difficulties in reactive cases are related to the competition between infiltration and reaction. The infiltration is more or less quickly limited by the precipitation of the new solid phases. Combined thermodynamic and kinetic models are found of prime importance to progress on this topic.
CQ-3:L09 The Production of Fire-resistant Fibre Metal Laminate (FML) and Low Cost CMC Components for Transport Applications
C. Mingazzini1, S. Bassi2, t. delise1, E. Leoni1, M. Scafè1, G. DE ALOYSIO3, 1ENEA TEMAF, Faenza, Italy; 2University of Pisa, Pisa, Italy; 3CertiMaC, Faenza, Italy
Being production of complex shape CMC still a challenge, FMLs represent an interesting alternative fire resistant solution for future mobility (e.g. low weight battery boxes). The main advantages of FMLs over CMC are lower production cost and embodied energy. Current commercially available FMLs are employed in aeronautics (Glare®) but they are not suitable for the automotive, because of being based on expensive raw materials (s-glass and aluminium foils) and limited range of achievable geometries (due to an Al thickness of 0.3-0.5 mm, necessary to ensure fire resistance). Moving from epoxy resin to biobased fire retardant PFA (Polyfurfuryl alcohol), enables to reach fire resistance (according to EN13501, 30 min at 750°C) using less thick Al (e.g. 0.1 mm) resulting in a higher flexibility of the semifinished material (Al+prepreg) for hand-layup lamination on moulds. Another change it is discussed in the present work is moving from s-glass to a much cheaper fibre, C2C recyclable aeronautical grade basalt. The optimisation of warm pressing and autoclave were investigated, along with end-of-life separation and the mechanical validation all indicating that the solution could be rapidly adopted for mass production in the automotive, with significant environmental advantages.
CQ-4:IL05 Image-based Modeling of Woven Ceramic Matrix Composites
G. Couégnat, J. Bénézech, V. Mazars, O. Caty, G.L. Vignoles, Laboratoire des Composites Thermostructuraux (CNRS/Univ.Bordeaux/Safran/CEA), Pessac, France
Woven ceramic matrix composites (CMC) exhibit excellent thermo-mechanical properties and can endure very high temperature. That makes them promising candidates to be used as components in hot parts of the next-generation aircraft engines. Yet, their modelling is quite challenging, mainly because of their intricate architecture. Numerical models need to capture their multiscale organization, and should at least accurately describe their woven fabric. With this aim, we have developed a multiscale image-based modeling framework that allows to construct high-fidelity models of CMCs at micro- and mesoscale. These digital twins are then used to perform virtual tests including the simulation of damage mechanisms. Ad hoc scale-bridging strategies have also been proposed to transfer the inherent variability of these materials at upper scales, and to cope with large structural models while keeping the required computational resources bearable. Our approach is eventually able to capture and to reproduce the complex interplay between the material architecture, the mechanical loading, and the damage development. The capability of our framework is illustrated through several examples, including comparisons with in situ micro-tomography tests.
CQ-4:IL09 Influence of Interphases on the Thermomechanical Behavior of CVI SiC/SiC Composites
C. SAUDER, J. BRAUN, C. FELLAH, M-H. BERGER, E. BUET, CEA SACLAY, Gif-Sur-Yvette, France
Ceramic Matrix Composites (CMCs) are largely studied for the improvement of safety of nuclear fission reactors and for a long time in fusion materials research programs. Silicon carbide-reinforced silicon carbide (SiC/SiC) composites are the most suitable for these applications related to the high stability of SiC phase under neutron irradiation. Nevertheless, final characteristics that are required represent a high challenge for scientific community. In such environment, Pyrocarbon interphase seems the most suitable and largely control the mechanical behavior of such materials. The object of present lecture is to provide an overview of composite interphases influence on the final mechanical behavior of composites. The microstructure and texture of Pyrocarbon, as well as the influence of fibre roughness and chemistry will be largely discussed related to mechanical behavior.
CQ-4:L10 Thermophysical and Thermomechanical Characterization of Ceramic Matrix Composites for the Energy-intensive Industry
L. Laghi1, G. De Aloysio1, C. Mingazzini2, S. Bassi3, M. Scafè2, P. FABBRI2, A. Noeth4, J. Maier4, 1Certimac soc.cons.ar.l., Faenza - RA, Italy; 2ENEA SSPT-PROMAS-TEMAF, Faenza - RA, Italy; 3CNR-ISTEC, Faenza - RA, Italy; 4Fraunhofer-Institute for Silicate Research ISC/Fraunhofer, Center for High Temperature Materials and Design, Bayreuth, Germany
The increasing use of renewable energy sources in the energy-intensive industry requires novel materials capable of withstanding high temperatures and corrosive environments while ensuring energy efficiency and high performances, such as Ceramic Matrix Composites (CMCs). The innovative microwave-assisted production process developed in CEM-WAVE Project (www.cem-wave.eu) exploits Microwave-assisted Chemical Vapour Infiltration (MW-CVI) technologies to reduce the high production costs of CMCs. In particular, the research investigated the properties of uncoated and fully coated SiC/SiC-CMC, one of the materials that can best meet the requirements of high thermophysical and thermomechanical performances. The thermophysical characterization was conducted with the Light Flash Technique (LFA), in order to determine thermal diffusivity, specific heat and thermal conductivity up to 1200°C. Mechanical characterization (mainly flexural tests) were performed in parallel with the optimisation of infiltration process. Environmental Barrier Coatings are also under development, tailoring CTE and adhesion on the substrate characteristics. The experimentation about LFA provided preliminary indications to reliably model and predict the potential behaviour of uncoated and fully coated SiC/SiC-CMC.
CQ-5:IL02 Microstructure-properties Relationships for the Machining of CMCs
R. GOLLER, A. RÖSIER, P. LEON-PEREZ, Augsburg University of Applied Sciences, Augsburg, Germany
Ceramic Matrix Composites (CMCs) become more important since the ceramic brakes for high performance cars and recently some components inside the aircraft gas-turbines have been commercialized. Anisotropic material properties and a wide range of material types however make process development and optimization difficult and a long term task. Final machining especially is very critical from various points of view. On the one hand the part is almost finished and therefore the risk of damage has to be avoided. On the other hand the effects of any machining operation on the material properties are almost unknown or not finally explored. For any series production the processes and its effects on the product performance has to be clearly defined. The presented work contributes to this challenge and shows the effect of some mechanical machining processes, like grinding and milling on surface roughness and mechanical properties of a special CMC material.
CQ-5:IL03 Studies on Carbon Fibrous Ablators: From Image-based Modeling to Experimental Determination of Reaction Constants from Plasma Jet Tests
G.L. Vignoles, X. Lamboley, P. Blaineau, C. Levet, O. Caty, University of Bordeaux - CNRS - CEA - Safran : LCTS, Pessac, France; A. Turchi, D. LE Quang Huy, O. Chazot, Von Karman Institute, Rhode-Saint-Genèse, Belgium; D. Bianchi, Università La Sapienza, Roma, Italy
Lightweight insulating refractories based on carbon fiber preforms, with up to 80% porosity, present exceptional thermal and chemical properties; they are incorporated in heat shields used to protect space capsules during very high-speed atmospheric entry. However, due to their very porous structure, their ablation is partly a volumetric phenomenon instead of surface-related only, turning more difficult the identification of their performances. This presentation will describe how analytic and image-based computational modeling help in simulating the material behavior. The simulation tools will be presented, and an application case involving pure nitrogen plasma torch tests, will be discussed.
CQ-6:IL01 C/C-SiC Composites for Next-generation Brake Disks
W. Krenkel, T. Opel, N. Langhof, University of Bayreuth, Bayreuth, Germany
A new approach for the design and manufacture of lightweight ceramic/metal hybrid brake disks is presented. Full-ceramic LSI-derived C/C-SiC brake disks have proven their outstanding tribological properties in high performance brake systems for automotive applications since many years. With the increasing replacement of combustion engines by electric engines, the requirements on the brake systems moves from a service to an emergency brake system, i.e. the material of the brake disk and pads have to withstand extreme requirements only few times. A new concept of a lightweight and cost-efficient ceramic/metal brake disk, comprising an aluminum load-bearing disk, lined with short-fiber reinforced C/C-SiC composite segments, is presented. A prototype for a mid-class sedan was designed on the basis of a thermal finite element analysis and different joining methods to integrate the ceramic composite into the metallic substructure were examined. The hybrid ceramic/metal component was manufactured and tested on a dynamometer to evaluate the tribological properties. The relationships between the frictional behavior (CoF, wear), the temperature profile in the aluminum load bearing structure and the ceramic linings as well as the bonding strengths of the ceramic/metal joints are discussed.
CQ-6:IL02 Silicon carbide and Silicon carbide based Fiber Composites for Fusion
M. FERRARIS, Politecnico di Torino, Torino, Italy
A limited number of materials have been proposed as structural materials for nuclear fusion reactors: silicon carbide (SiC) and silicon carbide based fiber composites (SiC/SiC) are among them. In order to use them as structural materials, one issue to be considered is their joining, in particular a fast joining process to be done without using any pressure and possibly with localized heating. Innovation in joining, coating and characterization of SiC-based components for nuclear energy production developed within our research group (www.composites.polito.it) will be summarized, together with a brief overview on J-TECH@POLITO, a recently funded Advanced Joining Technology research center at Politecnico di Torino (http://www.j-tech.polito.it/).
CQ-6:IL03 HB-Cesic Mirrors and Telescopes - From Design to Alignment
M.R. KROEDEL, Y. Baskaran, ECM Engineered Ceramic Materials GmbH, Moosinning, Germany
Future space missions requiring more and more larger optics and structures to increase the resolution therefore, new materials or improved systems are required to meet these challenging requirements for such missions. Especially, ceramic materials are a very promising material candidates to meet these challenging requirements for large size with minimized mass for future space telescopes. Beside an overview of different ceramic materials for optical telescopes this paper will present an approach for future space telescopes made out of HB-Cesic, a carbon fiber reinforced silicon carbide material to design such a-thermal systems with high optical performance. This paper is focused on existing technologies and telescope systems as well as future a-thermal hybrid systems combining different ceramic composite materials to develop large space optical telescopes with minimized mass.