Design and Manufacture of Ceramic Ceramic Composites for ... · PDF fileUniversity of Bayreuth...

University of BayreuthLehrstuhl Keramische Werkstoffe
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4th World Materials Research Institutes Forum (WMRIF-4)
Shenyang, China, May 22nd to 26th, 2011
Design and Manufacture of CeramicSafety Components
Ceramic Composites for High Temperature Applications
Walter KrenkelCeramic Materials Engineering (CME)University of Bayreuth, Germany
XXI Conference AIVItalian Association of Science and Technology
May 15 17, 2013Catania, Italy
Audi AG, Fraunhofer ISC Ceramic Composites, Snecma Propulsion Solide, Schunk Group

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Outline
Ceramic Matrix Composites (CMCs)
Concepts of Weak Fiber/Matrix Interphases
Processing and Properties
Design Aspects
Two Engineering Approaches
Ceramic Composites for Friction Applications (Brakes)Hybrid Ceramic-Metal Pipes for Power Plants (700 C, 350 bar)
Summary

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University and Wagner Festival City Bayreuth
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(Population: 75 000)
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Mass Specific Strength vs. Temperature of Structural Materials
, SiC/SiC

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Typical Properties of Different Structural Materials (at RT)
0.1-0.241030>621010-3050-150500-1000500-10007.8HT-Steel
>30>1021010-20150-210360-700360-7007.8Steel
1-33-1040-95-

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Structural ceramics with high damage tolerance Quasi-ductility (crack deflection, fiber-pullout) Microcrack pattern, low fiber/matrix bondings Fracture does not result in failure High mass-specific properties (density
2 2.5 g/cm3)
Ceramic Matrix Composites (CMC)
Monolithicceramic
Strain %
Cracks in thematrix
Fiber break/fiber pullout
Further crack formation in thematrix and crack deflection in the interphase
Stre
ss M
Pa
Zok, Evans and Mackin, 1995
Fiber
Matrix crack
Remainingstress
Fiber coating
Crack deflection
Fiber-pullout

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Sharp, non-reactiveinterfaceBetween fiber and matrix and fiber surface roughnessDebonding effects depend on the frictional term ( = CoF, = clampingstress normal to theinterface)
Fiber coating
In situ reaction of fiberand matrix during CMC fabricationa Interphase-fiber
debondb Diffuse debond
cracking(e.g. PyC, hBN)
PorousinterphaseDebonding and shearproperties derive from a succession of weakbridges betweenparticles in a porouslayer
MultilayerinterphaseHeterogeneousmultilayer structureswith a dual function:Diffuse crack deflectionand barrier to solid stateor gaseous reaction (e.g. pulsed CVD-C/SiC)
M. H. Lewis
Different Concepts of Fiber/Matrix Interfaces

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Multilayered Interphases by Pressure-Pulsed CVI Technique
Deposit of multilayered PyC, BN orSiC layer (20 to 50 nm thick)
PyC-B4C-PyC-SiC multilayered self-healing matrix
R. Naslain, High Temperature Ceramic Materials and Composites, 2010
CVI-SiC/SiC CVI-C/SiC

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Fiber Preforming
Adjustment of the F/M Interphase
CVI-Process PIP-Process LSI-Process
MachiningGrinding, milling, drilling
JoiningIn situ-joining
Form/force-locking
Coating/FinishingTBC/EBC
Isothermal
Temp. Gradient
Press. Gradient
Pulsing
Rapid-CVI
Typical Manufacturing Processes for Non-Oxide Ceramic Matrix Composites
Hybrid-Process
CVI + LSI
PIP + LSI
CVI + PIP

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LSI-C/C-SiC (DLR) PIP-C/SiC (EADS)
CVI-SiC/SiC (MT Aerospace)
Microstructures of Different CMC-Materials
NPC-OFC (EADS)

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Melt-Infiltration of Silicon into C/C-Preforms (Three Step LSI-Process)
Fiber ResinAdditives (opt.)
Conditioning
Compounding/Mixing
Warm Pressing and Curing
CFRP
Pyrolysis
C/C
First Machining (opt.)
Joining (opt.)
Siliconizing
C/SiC
Final Machining
In-process coating (opt.)
Reaction zone Diffusion of Si-atoms
F. Gern, Research Report DLR, 95-26
Capillary diameter [m] Time of infiltr
ation [sec]
Infil
trat
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heig
ht[m
]

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Reaction Mechanisms Between Silicon and Carbon
Solid-liquid reaction between carbon and Si(l) + C(s) SiC(s)molten silicon (LSI-process)
Solid-gas reaction between carbon and Si(v) + C(s) SiC(s)gaseous silicon
Direct solid-solid reaction at the contact Si(s) + C(s) SiC(s)surfaces between C and Si
Reaction of carbon with SiO 2 Si(s,l) + CO(v) SiO(v) + SiC(s)(at sufficient high CO-pressures) SiO(v) + 2 C(s) SiC(s) + CO(v)Gas-gas reaction between SiO and CO 3 SiO(v) + CO(v) SiC(s) + 2 SiO2(s)
Prime reaction for the MI-process is the solid-liquid reaction
First wetting of the carbon surfaces by Si-vapour results in an initial SiC layer
Highly exothermal reaction ( H = - 68 kJ/mol)

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C/SiC Composites with Different Interphases (No Fiber Coating)
SEM micrograph of a 2D fabric-reinforcedcomposite (cross section)
Composition 25.1% SiC(by weight) 72.5% C
2.4% SiThree different interphasesFiber/Matrix CF-SiC (strong)Fiber/Matrix CF-C (weak)Matrix/Matrix SiC-Si (strong)
C-fiber
AmorphousC-matrix
C/C-Segment
SiC
Residual siliconembedded in SiC
Strong bondings in the CF-SiC interphase
Weak bondings in the CF-C interphase

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250
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0
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100
150
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Biegefestigkeit Inter. Scherfestigkeit
Fest
igke
it M
Pa
RT900C1200C
47
5866
0
50
100
Biegesteifigkeit
Mod
ul G
Pa
Characteristic Properties of C/SiC CompositesSt
reng
thM
Pa
Flexural Strength ILSS Flexural Modulus
Mod
ulus
GPa
Increasing mechanicalproperties with higher servicetemperatures
Low safety factors
High anisotropic propertiesand big differences in CTEto metals
Design of strain-compatiblejoinings

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Carbon/Carbon Composites for Aircraft and Racing Cars
Brembo SGL Ceramic Brakes GmbHPANOX-based Aircraft Brake System
+ Low density of about 2 g/cm3
+ High mass-specific energy absorption
+ High thermal shock resistance
- Friction coefficient highly dependent on temperature and humidity
Not useable for road vehicles

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Status and Characteristics of Carbon/Ceramic Brake Disks
Increasingly used in luxury sedans and sports cars (> 150 000 rotors/year)More than 250 patents cover all aspects of the material composition, processing and design
+ Low density (below 2.5 g/cm3)+ High thermal shock resistance+ High energy absorption+ Extreme thermal stability
(up to 1350 C)+ High corrosion stability+ High friction stability, low wear
rates (lifetime brake)
- High costsCourtesy of Audi AG

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Comparison of Brake Materials (Typical RT-Properties)
> 1350

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