Carbon fibre reinforced silicon carbide (C/SiC, C/C-SiC) C/SiC

spore: profile
id: c-sic
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: Carbon fibre reinforced silicon carbide (C/SiC, C/C-SiC)
abbreviation: C/SiC
role: structural ceramic-matrix composite for hot structures and friction parts
category: composites
type: ceramic-matrix
summary: |
  Carbon fibre reinforced silicon carbide (C/SiC, C/C-SiC) is a ceramic-matrix composite made of carbon fibres in a silicon carbide matrix. Krenkel reports that the X-38 nose cap was made of LSI C/C-SiC by DLR and that the CVI C/SiC body flaps were built by MAN Technologie. NASA's X-38 flap paper gives a peak flap surface temperature that can reach as high as 1649 °C. The Krenkel comparison table gives a density of 1.9 to 2.0 g/cm3 for LSI C/C-SiC and 2.1 to 2.2 g/cm3 for CVI C/SiC.
best_for: Hot structures that must keep strength at high temperature and low mass, such as re-entry flaps and nose caps, rocket nozzles and engine flaps. Krenkel says the mass-specific properties are unsurpassed by other structural materials above 1,000 °C.
weakest_at: Uncoated use in air above about 450 °C, because the carbon fibres oxidise (Krenkel), and a brittle, low-strain failure mode that designers must allow for.
identity:
  formula: Carbon fibre preform with a silicon carbide matrix (C/SiC). LSI-made C/C-SiC also contains unreacted silicon and amorphous carbon in its matrix.
  source: krenkel
  where: Introduction (section I) and Table 1 caption; LSI matrix description in the section on processes
tags:
  environments:
    - re-entry
    - launch
  stresses:
    - extreme-heat
    - thermal-cycling
  applications:
    - structures
    - heat-shields
    - propulsion-and-tanks
    - mechanisms
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density, LSI C/C-SiC (DLR)
    value: 1.9
    value_high: 2
    bound: range
    unit: g/cm3
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      reinforcement: two-dimensional fabric, 0/90 degree fibre orientation
    method: Range printed in a manufacturers' comparison table (Krenkel Table 1; the author attributes the data to representative manufacturers)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Density
  - benchmark: density
    label: Density, CVI C/SiC (MAN, p,T-gradient)
    value: 2.1
    value_high: 2.2
    bound: range
    unit: g/cm3
    scope: material
    conditions:
      process: chemical vapour infiltration, p,T-gradient
      reinforcement: two-dimensional fabric, 0/90 degree fibre orientation
    method: Range printed in a manufacturers' comparison table (Krenkel Table 1)
    status: ground
    source: krenkel
    where: Table 1, column C/SiC (CVI p,T-gradient, MAN), row Density
  - benchmark: density
    label: Density, lab Cf/SiC CMC made by PIP
    value: 1.7
    unit: g/cm3
    scope: material
    conditions:
      fibre: T300 carbon fibre (density 1.8 g/cm3) with a 200 nm pyrocarbon coating
      process: tape-cast aqueous slurry with 66 vol% SiC, precursor impregnation and pyrolysis (PIP) for four cycles, then spark-plasma sintering
    method: Value stated in the research article text after four PIP cycles (Figure 1b)
    status: ground
    source: park2023
    where: Results, paragraph on Figure 1b; fibre density in Materials and Methods
  - benchmark: porosity
    label: Open porosity, LSI C/C-SiC (DLR)
    value: 2
    value_high: 5
    bound: range
    unit: '%'
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Porosity
  - benchmark: fibre_volume_content
    label: Fibre content, LSI C/C-SiC (DLR)
    value: 55
    value_high: 65
    bound: range
    unit: Vol%
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
    method: Range printed in Table 1 (manufacturers' comparison table); the text also gives typical fibre volume contents of 50 to 65 per cent for LSI C/C-SiC
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Fibre content; section on LSI matrix
  - benchmark: fibre_volume_content
    label: Fibre content, CVI C/SiC (MAN, p,T-gradient)
    value: 42
    value_high: 47
    bound: range
    unit: Vol%
    scope: material
    conditions:
      process: chemical vapour infiltration, p,T-gradient
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/SiC (CVI p,T-gradient, MAN), row Fibre content
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, LSI C/C-SiC (DLR)
    value: 80
    value_high: 190
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      reinforcement: two-dimensional fabric, 0/90 degree
      temperature: room temperature (the text states that Table 1 values are determined at room temperature)
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Tensile strength; text after Table 1
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, CVI C/SiC (MAN, p,T-gradient)
    value: 300
    value_high: 320
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: chemical vapour infiltration, p,T-gradient
      reinforcement: two-dimensional fabric, 0/90 degree
      temperature: room temperature
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/SiC (CVI p,T-gradient, MAN), row Tensile strength
  - benchmark: flexural_strength
    label: Flexural strength, LSI C/C-SiC (DLR)
    value: 160
    value_high: 300
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature: room temperature (Table 1 values)
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Flexural strength
  - benchmark: flexural_strength
    label: Flexural strength, CVI C/SiC (MAN, p,T-gradient)
    value: 450
    value_high: 500
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: chemical vapour infiltration, p,T-gradient
      temperature: room temperature (Table 1 values)
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/SiC (CVI p,T-gradient, MAN), row Flexural strength
  - benchmark: flexural_strength
    label: Flexural strength at room temperature, lab Cf/SiC CMC (PIP)
    value: 235
    unit: MPa
    scope: material
    conditions:
      fibre: T300 carbon fibre with pyrocarbon coating
      form: bars 1.5 mm by 2.0 mm by 30 mm cut from 150 micron doctor-blade tapes
      temperature: room temperature
      spread: standard deviation 44 MPa (150 micron tapes)
    method: Value stated in the research article text; the room-temperature test method is not named separately
    status: ground
    source: park2023
    where: Results, paragraph on Figure 3a
  - benchmark: flexural_strength
    label: Flexural strength at 1750 °C, lab Cf/SiC CMC (PIP)
    value: 434
    unit: MPa
    scope: material
    conditions:
      temperature: 1750 °C
      atmosphere: argon
      test: in situ flexural test following ASTM C1211-18
      fibre: T300 carbon fibre with pyrocarbon coating
    method: Value stated in the research article abstract and results; 84% above the room-temperature value
    status: ground
    source: park2023
    where: Abstract; Results, Figure 3a text
  - benchmark: flexural_strength
    label: Flexural strength at 2000 °C, lab Cf/SiC CMC (PIP)
    value: 542
    unit: MPa
    scope: material
    conditions:
      temperature: 2000 °C
      atmosphere: argon
      test: in situ flexural test following ASTM C1211-18
      fibre: T300 carbon fibre with pyrocarbon coating
    method: Value stated in the research article abstract and results
    status: ground
    source: park2023
    where: Abstract; Results, Figure 3a text
  - benchmark: elastic_modulus
    label: Young's modulus, LSI C/C-SiC (DLR)
    value: 50
    value_high: 70
    bound: range
    unit: GPa
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature: room temperature (Table 1 values)
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Young's modulus
  - benchmark: elastic_modulus
    label: Young's modulus, CVI C/SiC (MAN, p,T-gradient)
    value: 90
    value_high: 100
    bound: range
    unit: GPa
    scope: material
    conditions:
      process: chemical vapour infiltration, p,T-gradient
      temperature: room temperature (Table 1 values)
    method: Range printed in Table 1 (manufacturers' comparison table)
    status: ground
    source: krenkel
    where: Table 1, column C/SiC (CVI p,T-gradient, MAN), row Young's modulus
  - benchmark: cte
    label: Coefficient of thermal expansion, direction marked ⊥, LSI C/C-SiC (DLR)
    value: 2.5
    value_high: 7
    bound: range
    unit: 10-6 K-1
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature_range: room temperature to 1500 °C (Table 1 footnote 2)
      direction: the row marked ⊥ in the table, as printed
    method: Range printed in Table 1 (printed unit 10−6 K−1); the table gives its own footnote for the temperature range
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), coefficient of thermal expansion row marked ⊥, footnote (2)
  - benchmark: cte
    label: Coefficient of thermal expansion, direction marked ⊥, CVI C/SiC (SNECMA, isothermal)
    value: 5
    unit: 10-6 K-1
    scope: material
    conditions:
      process: chemical vapour infiltration, isothermal
      temperature_range: room temperature to 1000 °C (Table 1 footnote 1)
      direction: the row marked ⊥ in the table, as printed
    method: Value printed in Table 1 (printed unit 10−6 K−1)
    status: ground
    source: krenkel
    where: Table 1, column CVI (isothermal, SNECMA), coefficient of thermal expansion row marked ⊥, footnote (1)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, direction marked ⊥, LSI C/C-SiC (DLR)
    value: 7.5
    value_high: 10.3
    bound: range
    unit: W/mK
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature_range: 200 to 1650 °C (Table 1 footnote 3)
      direction: the row marked ⊥ in the table, as printed
    method: Range printed in Table 1 (printed unit W/mK)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), thermal conductivity row marked ⊥, footnote (3)
  - benchmark: specific_heat
    label: Specific heat, LSI C/C-SiC (DLR)
    value: 690
    value_high: 1550
    bound: range
    unit: J/kgK
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature_range: not printed for this column in Table 1 (the column has no temperature footnote)
    method: Range printed in Table 1; the temperature range for this cell is not given
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Specific heat
  - benchmark: elongation
    label: Strain to failure, LSI C/C-SiC (DLR)
    value: 0.15
    value_high: 0.35
    bound: range
    unit: '%'
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
      temperature: room temperature (Table 1 values)
    method: Printed as strain to failure in Table 1 and mapped to the elongation benchmark
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Strain to failure
  - benchmark: interlaminar_shear_strength
    label: Interlaminar shear strength, LSI C/C-SiC (DLR)
    value: 28
    value_high: 33
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
    method: Range printed in Table 1 (ILSS row)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Interlaminar shear strength
  - benchmark: compressive_strength
    label: Compression strength, LSI C/C-SiC (DLR)
    value: 210
    value_high: 320
    bound: range
    unit: MPa
    scope: material
    conditions:
      process: liquid silicon infiltration (LSI), C/C-SiC
    method: Range printed in Table 1 (compression strength row)
    status: ground
    source: krenkel
    where: Table 1, column C/C-SiC (LSI, DLR), row Compression strength
corrosion:
  - environment: Air or another oxidising atmosphere above about 450 °C
    headline: Uncoated carbon fibres degrade in an oxidising atmosphere above 450 °C, so long-term use in air needs an external coating.
    effect: Krenkel states that carbon fibres degrade in an oxidising atmosphere beyond 450 °C and that long-term use in air requires an external protective coating. The thermal values in the tables refer to inert conditions for this reason.
    rating: severe
    conditions:
      atmosphere: oxidising (air)
      temperature: above 450 °C (carbon fibres)
      basis: statement in the text, no test data given
    source: krenkel
    where: Introduction (section I) and the text on thermal properties after the tables
  - environment: CVD-SiC coated C/SiC cooled after coating and then heated to about 800 °C
    headline: A CVD-SiC coating cracks on cooling, and coated composites oxidise fastest at about 800 °C.
    effect: The mismatch in thermal expansion between CVD-SiC and the carbon fibre reinforcement cracks the coating, starting about 100 °C below the coating temperature. Krenkel states that coated composites show the highest oxidation rate at about 800 °C. Coatings reduce degradation only within a limited temperature range under static conditions and cannot prevent oxidation completely under dynamic conditions.
    rating: severe
    conditions:
      coating: CVD-SiC
      temperature: about 800 °C (highest oxidation rate)
      basis: statement in the text, no test data given
    source: krenkel
    where: Section on oxidation protection (section I, printed pages 118 to 119)
  - environment: Argon at 1500 °C to 2000 °C (precursor-derived SiC matrix)
    headline: A precursor-derived SiC matrix crystallises above 1400 °C, but the lab Cf/SiC CMC gained strength up to 2000 °C.
    effect: Park et al. state that conventional precursor-derived SiC crystallises above 1400 °C, shrinks by as much as 30% and cracks. In their ultrahigh-solids-loaded Cf/SiC CMC, flexural strength rose from 235 MPa at room temperature to 434 MPa at 1750 °C and 542 MPa at 2000 °C in argon. Park et al. also cite a SiCf/SiC PIP composite whose strength fell to 13% of its room-temperature value after heating in argon for 1 h at 1500 °C, which is a different material.
    rating: moderate
    conditions:
      atmosphere: argon
      temperature: 1400 °C and above (crystallisation); 1750 °C and 2000 °C (strength tests)
      basis: measured in the Park et al. study for their Cf/SiC CMC
    source: park2023
    where: Introduction; Results on flexural tests (Figure 3a); Discussion on the matrix (Figure 4 and Figure 5)
  - environment: Humid ambient air
    headline: Krenkel says C/C-SiC properties are not influenced by ambient humidity, which is one reason for its use in calibration plates.
    effect: Krenkel states that low-expansion C/C-SiC is used for calibration bodies because its properties are not influenced by ambient conditions such as humidity. No humidity test data are given in the text.
    rating: low
    conditions:
      environment: ambient humidity
      basis: statement in the text, no test data given
    source: krenkel
    where: Section 2.4 (Low-expansion structures)
  - environment: Air at high temperature, CVI C/SiC (NASA 2023 slide; coating status not stated)
    headline: NASA lists CVI C/SiC as having good oxidation resistance to about 3000 °F, while Krenkel says uncoated carbon fibres degrade above 450 °C in air.
    effect: NASA's 2023 briefing states "Good oxidation resistance to ~ 3000°F" for chemical vapour infiltration (CVI) C/SiC, with "Reasonable reusability". The slide does not say whether the part was coated or for how long it was exposed, and it shows no test data. Krenkel gives the 450 °C limit for uncoated carbon fibres, so the two sources describe different conditions and both are shown here.
    rating: moderate
    conditions:
      material: CVI C/SiC
      temperature: about 3000 °F as printed on the slide
      basis: statement on a slide, no test data shown
    source: ntrs-hypersonic-sic-2023
    where: Slide 'Selected Refractory Composites', bullet for chemical vapor infiltration (CVI) C/SiC
risks:
  hazards:
    - text: PubChem reports for silicon carbide (the matrix material, not the composite) that the chemical does not meet GHS hazard criteria for 70.3% (740 of 1053) of all reports, so most reports carry no hazard class.
      ghs: []
      source: pubchem-sic
      where: Safety and Hazards, GHS Classification (CID 9863)
    - text: PubChem lists H350i (May cause cancer by inhalation) in 16.6% of notifications and H372 (Causes damage to organs through prolonged or repeated exposure) in 16.1% of notifications for silicon carbide.
      ghs: []
      source: pubchem-sic
      where: Safety and Hazards, GHS Classification (CID 9863)
    - text: 'PubChem lists exposure limits for silicon carbide: nonfibrous forms 10 mg/m3 inhalable and 3 mg/m3 respirable; fibrous forms including whiskers 0.1 fibres per cc respirable.'
      ghs: []
      source: pubchem-sic
      where: Safety and Hazards, exposure limits (CID 9863)
  failure_risks:
    - mode: Oxidation of carbon fibres in air
      trigger: Use above about 450 °C in an oxidising atmosphere without an external coating
      consequence: Krenkel states that the fibres degrade and that long-term use in air needs an external protective coating
      severity: high
      source: krenkel
      where: Introduction (section I)
    - mode: Coating cracking and oxidation of a CVD-SiC coating
      trigger: Cooling after CVD-SiC deposition, because of the thermal expansion mismatch
      consequence: Cracks open in the coating, and the oxidation rate is highest at about 800 °C
      severity: moderate
      source: krenkel
      where: Section on oxidation protection (section I)
    - mode: Brittle failure at the design level
      trigger: Loads beyond the fibre pull-out range
      consequence: Krenkel says these materials are still very brittle from the viewpoint of a designer used to metals, although they have a quasi-ductile breaking behaviour and their damage tolerance is compared with grey cast iron as a first approximation
      severity: moderate
      source: krenkel
      where: Section on damage tolerance (section I)
    - mode: High bearing friction at the flap hinge
      trigger: CSiC bearings in the X-38 flap actuator
      consequence: NASA reports that MAN Technologie indicated the bearing coefficient of friction could exceed 0.7 or more, and that high-temperature CSiC bearing technology issues were part of the development problems
      severity: moderate
      source: ntrs-x38-flap
      where: Flap bearing and hinge discussion (flap actuator paper)
    - mode: Erosion of vane surfaces by exhaust particles
      trigger: Solid-fuel rocket exhaust carrying Al2O3 particles on jet vanes
      consequence: Krenkel states that vane surfaces need a protective CVD-SiC coating, and that the composite must balance fracture toughness against abrasion resistance
      severity: moderate
      source: krenkel
      where: Section 2.2 (vanes, nozzles and flaps of rocket motors)
  side_effects:
    - text: Krenkel states that the thermal expansion of the X-38 nose shell may amount to as much as 3 mm at a mean diameter of 700 mm at 1750 °C, so the mounting has to allow it.
      affects: Nose cap mounting and fastening to the fuselage
      source: krenkel
      where: Section on the X-38 nose cap (section 1, Figure 1)
  handling:
    - text: Krenkel states that the thermal properties in the tables refer to inert conditions, and that long-term use in air requires an external protective coating.
      source: krenkel
      where: Text on thermal properties after the tables
    - text: 'PubChem safety text for silicon carbide: avoid inhalation of dust.'
      source: pubchem-sic
      where: Safety and Hazards, handling (CID 9863)
  mitigations:
    - text: 'Krenkel describes multilayer oxidation protection: SiC layers with self-healing glass-forming layers based on oxides such as mullite, alumina or silicon, and pure β-SiC layers deposited by CVD for superior oxidation resistance.'
      source: krenkel
      where: Section I, oxidation protection
    - text: Park et al. attribute the high-temperature strength of their Cf/SiC CMC to an ultrahigh solids loading (66 vol%) and to the absence of sintering additives, which left no harmful secondary phase.
      source: park2023
      where: Discussion, paragraph on the matrix mechanism (Figure 4)
uses:
  - application: structures
    device: X-38 nose cap (LSI C/C-SiC, DLR)
    example: The nose cap was made of LSI C/C-SiC by DLR and is directly exposed to the stagnation region on re-entry, where temperatures of up to 1,800 °C occur during the re-entry phase (Krenkel). The expected temperature level for the nose cap is 1,750 °C.
    source: krenkel
    where: Section I (introduction) and section 1 (X-38 nose cap, Figure 1)
  - application: heat-shields
    device: X-38 body flaps (CVI C/SiC, MAN Technologie)
    example: The CVI C/SiC body flaps were 1,600 mm long and 1,500 mm broad, with more than 400 screws. Krenkel says the use of C/SiC gives about 50% weight reduction with higher safety margins compared with insulated metallic structures. NASA's flap paper says the flaps were built as a hot-structure CSiC composite with no thermal protection system, and that peak surface temperatures can reach 1649 °C (3000 °F).
    source: krenkel
    where: Section 1 (Figure 2, body flaps); NASA NTRS flap actuator paper, introduction
  - application: propulsion-and-tanks
    device: Upper-stage nozzle demonstrator (LPI C/SiC, filament winding, Ariane 5 upper stage)
    example: The demonstrator nozzle was 1,360 mm long with an exit diameter of 1,330 mm and a mass of 16 kg. Krenkel reports 60% weight reduction and an allowable temperature about 500 °C higher than superalloy Haynes 25.
    source: krenkel
    where: Section 2.2 (vanes, nozzles and flaps), nozzle paragraph
  - application: propulsion-and-tanks
    device: SNECMA M 88-2 outer engine flaps (military jet engine)
    example: Krenkel reports that the outer flaps in the SNECMA M 88-2 engine give 50% weight savings over the superalloy flap (Inconel 718), and that almost 300 flaps were fabricated for ground tests.
    source: krenkel
    where: Section 2.2, flaps paragraph
  - application: mechanisms
    device: Brake discs and pads (short-fibre C/C-SiC)
    example: Krenkel reports that C/C-SiC friction materials show open porosity below 5%, a density of about 2 g/cm3 and a ceramic share of at least 20% by mass, compared with carbon/carbon.
    source: krenkel
    where: Section 2.3 (brake disks and pads), paragraph on C/C-SiC properties
  - application: optics-and-cameras
    device: Optical unit tube and spider for a laser communication satellite (low-expansion C/C-SiC)
    example: Krenkel describes a laser communication satellite optical unit with a primary and secondary mirror on a low-expansion C/C-SiC tube and spider. No numerical performance values are given in the text.
    source: krenkel
    where: Section 2.4 (low-expansion structures), Figure 7
  - application: structures
    device: Calibration plates for coordinate measuring machines (C/C-SiC)
    example: A plate-shaped C/C-SiC calibrating body with an edge length of 420 mm, a thickness of 8 mm and 25 measurement holes. Krenkel says such bodies need a very low and constant thermal expansion coefficient across the normal temperature range of −30 to +50 °C.
    source: krenkel
    where: Section 2.4 (low-expansion structures), Figure 6
  - application: structures
    device: Half-scale non-tapered C/SiC body flap subcomponent (GE PSC, tested at NASA Dryden)
    example: Glass reports that in November 2003 the subcomponent was tested with simultaneous 2060°F heating and 100% design limit (mechanical) loading, and calls it the first combined load testing on a CMC control surface.
    source: ntrs-glass-2004
    where: Section on the C/SiC body flap subcomponent (IAC-04-V.5.09, Figure 8 caption and text)
  - application: mechanisms
    device: X-38 C/SiC hot-structure bearings
    example: NASA's 2023 briefing lists the X-38 C/SiC hot structures with bearings 50% lighter weight than traditional bearings, and notes that the X-38 C/SiC body flaps were provided by MT Aerospace.
    source: ntrs-hypersonic-sic-2023
    where: Slide 'Hot-Structure Weight Savings Over Insulated Cold Structure' (X-38 C/SiC hot structures bullet) and slide 'C/SiC Hot Structure'
supply:
  - subject: Silicon (silicon metal, the feedstock for the silicon carbide matrix)
    producers:
      - country: China
        share_percent: 87
        year: 2025
      - country: Brazil
        share_percent: 3.9
        year: 2025
      - country: Norway
        share_percent: 2.8
        year: 2025
      - country: France
        share_percent: 1.5
        year: 2025
      - country: Australia
        share_percent: 1
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (silicon added in the 2025 list, per the USGS silicon chapter)
        listed: true
      - list: 'EU critical raw materials list (Regulation (EU) 2024/1252, as shown on the European Commission page): Silicon metal'
        listed: true
    recycling: 'USGS silicon chapter: recycling is insignificant.'
    substitutes: []
    source: usgs-mcs2026-silicon
    where: World Production table, silicon metal, 2025 column (world total 4,600 thousand t; shares calculated by Space Mushroom against that total; the country rows sum to 4,590). The chapter also states that China accounted for almost 80% of global estimated production of silicon materials in 2025. Recycling line.
media: []
documents:
  - title: Carbon Fibre Reinforced Silicon Carbide Composites (C/SiC, C/C-SiC), Walter Krenkel, University of Bayreuth (PDF copy, printed pages 117 to 150)
    type: paper
    url: https://home.agh.edu.pl/~nmos1/TPCP/fall_2017_18/TPCP_seminar/introduction_to_ceramics_and_its_technology/C-C_SiC_composites-its_technology_applications_and_performance.pdf
  - title: Cf/SiC Ceramic Matrix Composites with Extraordinary Thermomechanical Properties up to 2000 °C (Nanomaterials, open access)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC10780313/
    year: 2023
  - title: Mineral Commodity Summaries 2026, Silicon
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
  - title: PubChem compound record, Silicon carbide (CID 9863)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Silicon-carbide
    year: 2026
  - title: The X-38 V-201 Flap Actuator Mechanism (NASA NTRS 20040084285)
    type: report
    url: https://ntrs.nasa.gov/citations/20040084285
    year: 2004
  - title: NASA HTP SiC/SiC Research for Hypersonic Airframe Hot Structures (Hypersonic Weapons Summit slides, September 2023)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20230012520/downloads/230910%20FINAL%20Glass%20HWS%20Airframe%20Hot%20Structures0918.pdf
    year: 2023
  - title: Airframe Technology Development for Next Generation Launch Vehicles (D. E. Glass, IAC-04-V.5.09, NASA NTRS 20050031174)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20050031174/downloads/20050031174.pdf
    year: 2004
gaps:
  - Flight status of the C/SiC parts is not confirmed. The NTRS paper calls the V-201 a space flight test article and cites drop tests at Dryden (V132, V131R), and the Krenkel text describes ground qualification. No fetched source shows a flight of the C/SiC flaps or nose cap, so the brief's 'flight-proven' wording is not used in this profile.
  - Radiation, atomic oxygen, UV, vacuum outgassing and thermal-vacuum data for C/SiC were not found in any fetched source.
  - The Krenkel chapter's publication year is not printed in the copy read, so the year is not given in its document entry or in its source entry.
  - Table 1 has a first, unlabelled row for coefficient of thermal expansion and thermal conductivity whose direction is not stated, so those values were left out. The CVI C/SiC thermal conductivity cell printed as '6.5–5.9' (reversed range, direction marked ⊥) was also left out.
  - Specific heat for LSI C/C-SiC is given without a temperature range because Table 1 has no footnote for that cell.
  - Porosity, fibre content, compression strength and interlaminar shear strength are not names in the property canon. Snake_case benchmarks were used for them.
  - Carbon fibre production and feedstock shares (PAN, pitch or other precursors) were not found in a fetched source, so no carbon supply shares are given.
  - Silicon crustal abundance was not found in a fetched source.
  - PubChem's GHS block for silicon carbide mixes notifications, including one block with H225 and H315 at 100%, which does not fit a solid ceramic. Only the aggregate 70.3% figure and the H350i and H372 percentages were used. No SDS for a C/SiC product was read, and the PubChem record is for silicon carbide, not the composite.
  - No dust or inhalation data for machined or ground C/SiC (carbon plus SiC) were found.
  - No designations (UNS, EN, DIN, JIS or trade names) are listed, because no fetched source printed a designation for C/SiC.
  - Park et al. do not name the room-temperature flexural test method. ASTM C1211-18 is named for the elevated-temperature in situ tests only.
  - No long-term ageing data in air (thousands of hours) were found. The Krenkel text gives only qualitative statements about oxidation.
  - The sources give no direct comparison between C/SiC and monolithic silicon carbide, so the comparison paragraph uses the superalloys named in the text and the Table 1 grades.
  - No image was checked for licence in this run, so the media key is empty.
  - The DLR project page for the X-38 nose cap could not be opened (certificate error), so no DLR statement was used.
  - The 2023 NASA briefing prints "Qualified for flight" for the X-38 C/SiC body flaps and "Flown by European Space Agency (ESA)" for CVI C/SiC in general. It names no mission, date or part for either, so the flight status above is unchanged and still unconfirmed for the C/SiC flaps and nose cap.
  - The 2004 Glass paper gives the 2003 combined-load test at NASA Dryden with simultaneous 2060°F heating and 100% design limit loading, but the text read in this run gives no measured strain, deflection or failure load for that test, so no test result is given.
  - No uncoated C/SiC oxidation test data over time (hours at a stated temperature in air) were found. The 3000 °F figure in the 2023 briefing is a statement, not a test result.
sources:
  krenkel:
    title: Carbon Fibre Reinforced Silicon Carbide Composites (C/SiC, C/C-SiC)
    id: Walter Krenkel, University of Bayreuth, Ceramic Materials Engineering (chapter PDF copy, printed pages 117 to 150; year not printed in the copy read)
    url: https://home.agh.edu.pl/~nmos1/TPCP/fall_2017_18/TPCP_seminar/introduction_to_ceramics_and_its_technology/C-C_SiC_composites-its_technology_applications_and_performance.pdf
    kind: handbook
    license: copyright, cited and not reproduced
  park2023:
    title: Cf/SiC Ceramic Matrix Composites with Extraordinary Thermomechanical Properties up to 2000 °C
    id: doi:10.3390/nano14010072 (Nanomaterials 14(1), 72; PMC10780313)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC10780313/
    year: 2023
    kind: paper
    license: open-access article on PMC; licence not read in this run
  usgs-mcs2026-silicon:
    title: Mineral Commodity Summaries 2026, Silicon
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, list of 34 critical raw materials under Regulation (EU) 2024/1252)
    id: Regulation (EU) 2024/1252
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
  pubchem-sic:
    title: PubChem compound record, Silicon carbide (CID 9863; molecular formula CSi; molecular weight 40.096 g/mol)
    id: CID 9863
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Silicon-carbide
    year: 2026
    kind: database
    license: public domain (NCBI)
  ntrs-x38-flap:
    title: The X-38 V-201 Flap Actuator Mechanism (Hagen, Moore, Estes and Layer)
    id: NASA NTRS 20040084285
    url: https://ntrs.nasa.gov/citations/20040084285
    year: 2004
    kind: report
    license: public domain (NASA)
  ntrs-hypersonic-sic-2023:
    title: NASA HTP SiC/SiC Research for Hypersonic Airframe Hot Structures (Glass, Kubitschek and Chenenko, Hypersonic Weapons Summit slides)
    id: NASA NTRS 20230012520
    url: https://ntrs.nasa.gov/api/citations/20230012520/downloads/230910%20FINAL%20Glass%20HWS%20Airframe%20Hot%20Structures0918.pdf
    year: 2023
    kind: report
    license: public domain (NASA)
  ntrs-glass-2004:
    title: Airframe Technology Development for Next Generation Launch Vehicles (D. E. Glass, IAC-04-V.5.09)
    id: NASA NTRS 20050031174; IAC-04-V.5.09
    url: https://ntrs.nasa.gov/api/citations/20050031174/downloads/20050031174.pdf
    year: 2004
    kind: report
    license: public domain (NASA)
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 22
  unreachable: 1
  caveats: 3
  note: Written by an AI assistant on 2026-11-01 from pages fetched in this run. Values were copied from the printed text or tables. The DLR page could not be opened and is not cited.
story:
  recipe:
    line: 'C/SiC is a carbon fibre preform infiltrated with a silicon carbide matrix. Krenkel describes four routes: chemical vapour infiltration (CVI), liquid polymer infiltration (LPI), liquid silicon infiltration (LSI) and precursor impregnation and pyrolysis (PIP). LSI C/C-SiC has a heterogeneous matrix of silicon carbide crystals, unreacted silicon and amorphous carbon, with about 55 to 65 vol% fibre. Park et al. made a Cf/SiC CMC by tape casting an aqueous 66 vol% SiC slurry through T300 fibres, then ran four PIP cycles and spark-plasma sintering, with pyrolysis at 1500 °C.'
    parts:
      - name: Carbon fibre (reinforcement)
        symbol: C
        share: 55 to 65 vol% in LSI C/C-SiC; 42 to 47 vol% in CVI C/SiC (Table 1)
        role: Carries the load and gives the composite its damage tolerance. The fibres are pulled out as cracks pass through the matrix, which is what keeps the composite from failing in a brittle way.
      - name: Silicon carbide (matrix)
        symbol: SiC
        atoms: 11
        atomic_weight: 40.096
        role: Krenkel gives its high oxidation resistance and thermal shock stability as the reasons for choosing it as the matrix. Molecular weight 40.096 g/mol (PubChem, CID 9863).
      - name: Pyrolytic carbon (fibre coating)
        symbol: C
        share: 200 nm coating on T300 fibres (Park et al.)
        role: Weak interphase between fibre and matrix, so that cracks deflect along it and the fibres can pull out.
      - name: Silicon and amorphous carbon (LSI matrix only)
        symbol: Si
        share: not printed in the source
        role: Unreacted silicon and amorphous carbon left in the LSI matrix (Krenkel). Their share is not printed.
  risk_groups:
    - title: For people
      level: 0
      verdict: Hazard notifications exist for silicon carbide dust
      lead: The composite itself is not described in the sources read. The PubChem notifications for silicon carbide, the matrix material, include cancer and organ-damage classes for inhalation, and most reports carry no hazard class.
      points:
        - label: Dust
          line: PubChem lists H350i (May cause cancer by inhalation) for 16.6% of notifications and H372 (Causes damage to organs through prolonged or repeated exposure) for 16.1% of notifications for silicon carbide. Avoid breathing dust from cutting or grinding.
        - label: Exposure limits
          line: PubChem lists 10 mg/m3 inhalable and 3 mg/m3 respirable for nonfibrous silicon carbide, and 0.1 fibres per cc respirable for fibrous forms including whiskers.
    - title: If a part overheats in air
      lead: These are statements from Krenkel, not test results on finished parts.
      points:
        - label: Carbon fibres
          line: Above about 450 °C in an oxidising atmosphere the carbon fibres degrade, so long-term use in air needs an external coating.
        - label: Coating cracks
          line: A CVD-SiC coating cracks on cooling because its thermal expansion differs from the fibre reinforcement. The highest oxidation rate is at about 800 °C.
        - label: Flap hinge
          line: NASA reports that MAN Technologie indicated the bearing coefficient of friction could exceed 0.7 or more in the X-38 flap bearings.
    - title: Handling and storage
      points:
        - label: Atmosphere
          line: Krenkel's thermal values are for inert conditions. Keep the material away from oxidising conditions where possible.
        - label: Dust
          line: PubChem's safety text for silicon carbide says to avoid inhaling dust.
  why: 'Carbon fibre reinforced silicon carbide (C/SiC) pairs carbon fibres with a silicon carbide matrix. Krenkel explains that carbon fibres alone degrade in an oxidising atmosphere above 450 °C, and that silicon carbide is used as the matrix because of its high oxidation resistance and thermal shock stability. The fibres keep the composite from failing like a monolithic ceramic. The result is a hot structure: Krenkel says these materials are low in density and keep their properties at high temperature, and NASA reports flap surfaces that can reach 1649 °C during re-entry.'
  uses:
    - where: Re-entry hot structures (X-38)
      line: The X-38 nose cap was made of LSI C/C-SiC by DLR. The CVI C/SiC body flaps were built by MAN Technologie and were 1,600 mm long and 1,500 mm broad. Krenkel says the C/SiC body flaps give about 50% weight reduction compared with insulated metallic structures.
    - where: Rocket and jet-engine hot parts
      line: A C/SiC nozzle demonstrator for the Ariane 5 upper stage was 1,360 mm long and weighed 16 kg. Krenkel reports 60% weight reduction and an allowable temperature about 500 °C higher than the superalloy Haynes 25. The SNECMA M 88-2 outer flaps save 50% weight against Inconel 718.
    - where: Brakes and friction parts
      line: C/C-SiC brake discs and pads have an open porosity below 5%, a density of about 2 g/cm3 and at least 20% ceramic content by mass, which gives them wear resistance that Krenkel compares favourably with carbon/carbon.
    - where: Low-expansion metrology and optics
      line: A C/C-SiC calibration plate with a 420 mm edge length, 8 mm thickness and 25 holes must keep a very low, constant thermal expansion across −30 to +50 °C. Krenkel also describes a laser communication satellite optical unit on a C/C-SiC tube and spider, without numerical values in the text.
  can_do:
    - label: Heat
      benchmark: flexural_strength
      line: Park et al. measured a flexural strength of 434 MPa at 1750 °C and 542 MPa at 2000 °C in argon for their lab Cf/SiC CMC, against 235 MPa at room temperature. Krenkel gives an expected temperature of 1,750 °C for the X-38 nose cap.
    - label: Mass
      benchmark: density
      line: LSI C/C-SiC has a density of 1.9 to 2.0 g/cm3 and CVI C/SiC 2.1 to 2.2 g/cm3 (Table 1). The C/SiC body flaps are about 50% lighter than insulated metallic structures, according to Krenkel.
    - label: Dimensional stability
      benchmark: cte
      line: Krenkel's Table 1 gives a coefficient of thermal expansion of 2.5 to 7 10-6 K-1 for LSI C/C-SiC in the direction marked ⊥, from room temperature to 1500 °C. The nose-shell thermal growth of 3 mm at 700 mm diameter at 1750 °C shows why mounting must allow for expansion.
    - label: Re-entry temperature
      line: NASA reports that the X-38 flaps can reach peak surface temperatures as high as 1649 °C (3000 °F), and Krenkel gives up to 1,800 °C during re-entry in general.
  compare: 'Krenkel compares C/SiC with superalloys: the SNECMA M 88-2 outer flaps save 50% weight against Inconel 718, and the Ariane 5 nozzle demonstrator saves 60% weight at an allowable temperature about 500 °C higher than Haynes 25. Within the C/SiC family, LSI C/C-SiC is lighter and less porous than the CVI gradient C/SiC: 1.9 to 2.0 g/cm3 and 2 to 5% porosity, against 2.1 to 2.2 g/cm3 and 10 to 15% porosity for CVI. CVI C/SiC is stronger in tension (300 to 320 MPa against 80 to 190 MPa for LSI C/C-SiC), so the process chosen depends on whether weight or tensile strength matters more.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Flexural strength
      benchmark: flexural_strength
    - label: Coefficient of thermal expansion
      benchmark: cte
  handling:
    - Keep the material in an inert or low-oxygen atmosphere where possible. The printed thermal values are for inert conditions, and long-term use in air needs an external coating (Krenkel).
    - Avoid breathing dust, including dust from cutting or grinding (PubChem silicon carbide safety text).
    - 'Allow for thermal growth: the X-38 nose shell can grow about 3 mm at a 700 mm mean diameter at 1750 °C (Krenkel).'
  good_for:
    - High-temperature hot structures. Park et al. report 542 MPa flexural strength at 2000 °C for their lab Cf/SiC CMC.
    - Low-expansion parts. LSI C/C-SiC has a coefficient of thermal expansion of 2.5 to 7 10-6 K-1 from room temperature to 1500 °C, and Krenkel cites calibration plates for this reason.
    - Weight-critical flaps and nozzles. Krenkel reports 50% weight savings for the C/SiC body flaps and for the SNECMA M 88-2 outer flaps.
  watch_out:
    - Oxidation. Carbon fibres degrade in an oxidising atmosphere above about 450 °C, so uncoated parts need protection for long use in air.
    - Coating cracks. CVD-SiC coatings crack on cooling, and oxidation is fastest near 800 °C.
    - Lower tensile strength in LSI grades. LSI C/C-SiC gives 80 to 190 MPa against 300 to 320 MPa for the CVI gradient C/SiC.
    - Brittle failure at the design level. Krenkel says these materials are still very brittle from the viewpoint of a designer used to metals.
  verdict: C/SiC is the high-temperature structural choice where weight and heat both matter, and the sources read here support its use in hot structures and friction parts. It is brittle at the design level and needs oxidation protection for long use in air, so the sources support design with care rather than a drop-in replacement for metals.