spore: profile
id: as4-3501-6
spore_version: 0.2
family: carbon-epoxy
name: Hexcel AS4/3501-6 carbon-epoxy
abbreviation: AS4/3501-6
role: structural composite laminate (graphite/epoxy facesheets in a sandwich)
category: composites
type: carbon-fiber-reinforced
summary: |
  Hexcel AS4/3501-6 is a graphite/epoxy composite. It uses AS4 PAN-based carbon fibre woven as 8-harness satin fabric of 3K tows, in a 3501-6 epoxy resin. NASA Marshall tested it as the facesheet material of the Space Shuttle solid rocket booster composite nose cap. In the NASA lamina tests at 75 °F, the warp tensile strength averaged 111.6 ksi and the A-basis value was 98.0 ksi. The glass transition temperature of the unconditioned laminate was 386 °F by DMA and 380 °F by DSC.
best_for: Flight-heritage structural laminates where a 350 °F service range is needed (NASA tested warp tensile strength at 350 °F and 480 °F)
weakest_at: Strength and stiffness fall steeply above 350 °F and near 600 °F. Moisture lowers the glass transition temperature (NASA)
identity:
  formula: Woven 8H harness AS4 carbon fibre (PAN-based, 3K tows, 94.0% carbon) in a 3501-6 epoxy resin matrix; the resin chemistry is not printed in the sources read
  source: nasa-tm-2000-210252
  where: Section 2.1 (Materials and Processing), which names the AS4/3501-6 8H harness fabric of 3K tows; carbon content from the Hexcel AS4 datasheet, Carbon Content row
tags:
  environments: []
  stresses:
    - moisture
    - high-temperature
  applications:
    - structures
    - heat-shields
properties:
  - benchmark: ultimate_tensile_strength
    label: Warp tensile strength, lamina, average
    value: 111.6
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average of lots as summarised in the table
      test: ASTM D 3039 (tensile), per the report Table 1
    method: Lamina tensile average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Tensile stress (ksi), 75 °F Average column
  - benchmark: ultimate_tensile_strength
    label: Warp tensile strength, lamina, A-basis
    value: 98
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: A-basis statistical allowable as printed by NASA
    method: A-basis lamina allowable as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Tensile stress (ksi), 75 °F A-Basis column
  - benchmark: ultimate_tensile_strength
    label: Fill tensile strength, lamina, average
    value: 104.6
    unit: ksi
    scope: material
    conditions:
      orientation: fill (90 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average of lots as summarised in the table
    method: Lamina tensile average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Fill Tensile stress (ksi), 75 °F Average column
  - benchmark: ultimate_tensile_strength
    label: Warp tensile strength at 350 °F (after heating to 600 °F)
    value: 93.9
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      temperature: 350 °F
      pre_treatment: initially heated to 600 °F, then cooled to 350 °F (the report marks these samples with an asterisk)
      basis: average
    method: Lamina tensile average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Tensile stress (ksi), 350 °F* Average column; the report defines the asterisk in the Table 6 footnotes and Section 5
  - benchmark: ultimate_tensile_strength
    label: Warp tensile strength at 550 °F
    value: 74.8
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      temperature: 550 °F
      basis: average
    method: Lamina tensile average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Tensile stress (ksi), 550 °F Average column
  - benchmark: ultimate_tensile_strength
    label: Warp tensile strength at 480 °F
    value: 74.6
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      temperature: 480 °F
      basis: average
    method: Lamina tensile average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Tensile stress (ksi), 480 °F Average column
  - benchmark: elastic_modulus
    label: Warp tensile modulus, lamina, average
    value: 9.8
    unit: Msi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average (standard deviation 0.4 Msi printed alongside)
    method: Lamina modulus average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), second lamina table, Warp Tensile modulus (Msi), 75 °F Average column
  - benchmark: elastic_modulus
    label: Fill tensile modulus, lamina, average
    value: 9.7
    unit: Msi
    scope: material
    conditions:
      orientation: fill (90 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average (standard deviation 0.4 Msi printed alongside)
    method: Lamina modulus average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), second lamina table, Fill Tensile modulus (Msi), 75 °F Average column
  - benchmark: compressive_strength
    label: Warp compressive strength, lamina, average
    value: 82.9
    unit: ksi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average
    method: Lamina compression average as printed in the NASA lamina summary table (ASTM D 695 per Table 1)
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Compr. stress (ksi), 75 °F Average column
  - benchmark: compressive_modulus
    label: Warp compressive modulus, lamina, average
    value: 8.7
    unit: Msi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average (standard deviation 0.7 Msi printed alongside)
    method: Lamina modulus average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), second lamina table, Warp Compr. modulus (Msi), 75 °F Average column
  - benchmark: in_plane_shear_strength
    label: In-plane shear strength, +45 degree lamina, average
    value: 13.3
    unit: ksi
    scope: material
    conditions:
      orientation: +45 degree (balanced biaxial laminate)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average
    method: Lamina in-plane shear average as printed in the NASA lamina summary table (ASTM D 3518 per Table 1)
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, 45 In-Plane shear (ksi), 75 °F Average column
  - benchmark: shear_modulus
    label: In-plane shear modulus, +45 degree lamina, average
    value: 730.5
    unit: ksi
    scope: material
    conditions:
      orientation: +45 degree (balanced biaxial laminate)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average (standard deviation 56.0 ksi printed alongside)
    method: Lamina shear modulus average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), second lamina table, 45 Shear modulus (ksi), 75 °F Average column
  - benchmark: interlaminar_shear_strength
    label: Warp interlaminar shear strength, average
    value: 7040
    unit: psi
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: average (ASTM D 3846 per Table 1)
    method: Lamina interlaminar shear average as printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Interlaminar shear (psi), 75 °F Average column
  - benchmark: poissons_ratio
    label: Warp Poisson's ratio, lamina
    value: 0.06
    unit: '-'
    scope: material
    conditions:
      orientation: warp (0 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: printed in the 75 °F column of the lamina table; the column is not labelled average or A-basis
    method: Value printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Warp Poisson's ratio row
  - benchmark: poissons_ratio
    label: Fill Poisson's ratio, lamina
    value: 0.07
    unit: '-'
    scope: material
    conditions:
      orientation: fill (90 degree)
      form: 8H harness fabric of 3K tows, graphite/epoxy lamina
      temperature: 75 °F
      basis: printed in the 75 °F column of the lamina table; the column is not labelled average or A-basis
    method: Value printed in the NASA lamina summary table
    status: ground
    source: nasa-tm-2000-210252
    where: Table 6 (report page 18), Lamina Level Tests, Fill Poisson's ratio row
  - benchmark: glass_transition_temperature
    label: Glass transition temperature, unconditioned, DMA
    value: 386
    unit: °F
    scope: material
    conditions:
      state: unconditioned ambient laminate
      method_detail: dynamic mechanical analyzer (DMA)
    method: Measured by DMA as printed in Section 2.3 (Moisture Conditioning) of the NASA report
    status: ground
    source: nasa-tm-2000-210252
    where: Section 2.3 (Moisture Conditioning), Tg paragraph; the paragraph says the ambient samples had Tg values of 386 and 380 °F from DMA and DSC
  - benchmark: glass_transition_temperature
    label: Glass transition temperature, unconditioned, DSC
    value: 380
    unit: °F
    scope: material
    conditions:
      state: unconditioned ambient laminate
      method_detail: dynamic scanning calorimeter (DSC)
    method: Measured by DSC as printed in Section 2.3 (Moisture Conditioning) of the NASA report
    status: ground
    source: nasa-tm-2000-210252
    where: Section 2.3 (Moisture Conditioning), Tg paragraph
  - benchmark: glass_transition_temperature
    label: Glass transition temperature, dry, DMA
    value: 398
    unit: °F
    scope: material
    conditions:
      state: dried for 24 hr at 250 °F before test (the report calls this the initial dry Tg)
      method_detail: dynamic mechanical analyzer (DMA)
    method: Measured by DMA as printed in Section 2.3 (Moisture Conditioning) of the NASA report
    status: ground
    source: nasa-tm-2000-210252
    where: Section 2.3 (Moisture Conditioning), Tg paragraph
  - benchmark: fiber_volume_fraction
    label: Fibre volume of the cured graphite/epoxy laminate
    value: 59.9
    value_high: 62.7
    bound: range
    unit: '%'
    scope: material
    conditions:
      laminate: 6-, 8- and 10-ply AS4/3501-6 laminates (per-laminate values 59.9, 62.7 and 61.6 percent)
      method_detail: acid digestion of the matrix, ASTM D 3171 Procedure A (nitric acid)
    method: Measured by acid digestion and reported as printed in the NASA report
    status: ground
    source: nasa-tm-2000-210252
    where: Section 2.1 (Materials and Processing), acid digestion paragraph
  - benchmark: fabric_areal_weight
    label: Areal weight of the 8H AS4/3501-6 fabric
    value: 370
    unit: g/m2
    scope: material
    conditions:
      form: AS4 3K tow 8H harness fabric, as used for the SRB nose cap
    method: Value printed in the NASA report
    status: ground
    source: nasa-tm-2000-210252
    where: Section 2.1 (Materials and Processing), acid digestion paragraph (fabric aerial weight, printed as 370 g/m2)
  - benchmark: ultimate_tensile_strength
    label: AS4 carbon fibre tow tensile strength (fibre, not laminate)
    value: 4433
    unit: MPa
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre tow, PAN-based, 3K, 6K and 12K counts
      basis: typical fibre property; printed as 643 ksi (4,433 MPa)
      test: not printed on the datasheet
    method: Typical fibre property from the Hexcel AS4 product data sheet (fibre, not the laminate)
    status: ground
    source: hexcel-as4-datasheet
    where: Typical Fiber Properties table, Tensile Strength row
  - benchmark: elastic_modulus
    label: AS4 carbon fibre tow tensile modulus (fibre, not laminate)
    value: 231
    unit: GPa
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre tow
      basis: typical fibre property; printed as 33.5 Msi (231 GPa), chord 6000-1000
    method: Typical fibre property from the Hexcel AS4 product data sheet (fibre, not the laminate)
    status: ground
    source: hexcel-as4-datasheet
    where: Typical Fiber Properties table, Tensile Modulus (Chord 6000-1000) row
  - benchmark: elongation
    label: AS4 carbon fibre tow ultimate elongation (fibre, not laminate)
    value: 1.8
    unit: '%'
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre tow
    method: Typical fibre property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Typical Fiber Properties table, Ultimate Elongation at Failure row
  - benchmark: density
    label: AS4 carbon fibre density (fibre, not laminate)
    value: 1.79
    unit: g/cm3
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre
      basis: printed as 0.0647 lb/in3 (1.79 g/cm3)
    method: Typical fibre property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Typical Fiber Properties table, Density row
  - benchmark: cte
    label: AS4 carbon fibre coefficient of thermal expansion (fibre, not laminate)
    value: -0.63
    unit: ppm/ºC
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre yarn
      basis: printed as -0.35 ppm/ºF (-0.63 ppm/ºC)
      direction: not stated on the datasheet
    method: Typical yarn property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Yarn/Tow Characteristics table, Coefficient of Thermal Expansion row
  - benchmark: thermal_conductivity
    label: AS4 carbon fibre thermal conductivity (fibre, not laminate)
    value: 6.83
    unit: W/m-ºK
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre yarn
      basis: printed as 3.95 Btu/hr-ft-ºF (6.83 W/m-ºK)
    method: Typical yarn property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Yarn/Tow Characteristics table, Thermal Conductivity row
  - benchmark: specific_heat
    label: AS4 carbon fibre specific heat (fibre, not laminate)
    value: 0.27
    unit: cal/g-°C
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre yarn
      basis: printed as 0.279 Btu/lb-°F (0.27 cal/g-°C)
    method: Typical yarn property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Yarn/Tow Characteristics table, Specific Heat row
  - benchmark: electrical_resistivity
    label: AS4 carbon fibre electrical resistivity (fibre, not laminate)
    value: 0.0017
    unit: ohm-cm
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre yarn
      basis: printed as 5.6 x 10-5 ohm-ft (1.7 x 10-3 ohm-cm)
    method: Typical yarn property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Yarn/Tow Characteristics table, Electrical Resistivity row
  - benchmark: filament_diameter
    label: AS4 carbon filament diameter
    value: 7.1
    unit: microns
    scope: material
    conditions:
      form: HexTow AS4 carbon fibre filament
      basis: printed as 0.280 mil (7.1 microns)
    method: Typical fibre property from the Hexcel AS4 product data sheet
    status: ground
    source: hexcel-as4-datasheet
    where: Typical Fiber Properties table, Filament Diameter row
  - benchmark: ultimate_tensile_strength
    label: Transverse tensile strength, unidirectional lamina, 22 °C, dry, high strain rate
    value: 59.3
    unit: MPa
    scope: material
    conditions:
      orientation: transverse (90 degree)
      form: unidirectional AS4/3501-6 graphite/epoxy, not the 8H fabric
      temperature: 22 °C (72 °F)
      moisture: 0 %
      strain_rate: high
    method: Average transverse tensile strength as printed in NASA CR-187229 Table 5.1
    status: ground
    source: nasa-cr-187229
    where: Table 5.1, Average transverse tensile properties for unidirectional AS4/3501-6, Transverse Tensile Strength row, High strain rate, 0% moisture 22 C column (printed as 59.3 MPa with 8.60 ksi)
  - benchmark: ultimate_tensile_strength
    label: Transverse tensile strength, unidirectional lamina, 22 °C, 1% moisture, high strain rate
    value: 40.8
    unit: MPa
    scope: material
    conditions:
      orientation: transverse (90 degree)
      form: unidirectional AS4/3501-6 graphite/epoxy, not the 8H fabric
      temperature: 22 °C (72 °F)
      moisture: 1 %
      strain_rate: high
    method: Average transverse tensile strength as printed in NASA CR-187229 Table 5.1
    status: ground
    source: nasa-cr-187229
    where: Table 5.1, Average transverse tensile properties for unidirectional AS4/3501-6, Transverse Tensile Strength row, High strain rate, 1% MOISTURE 22 C column (printed as 40.8 MPa with 5.92 ksi)
  - benchmark: elastic_modulus
    label: Transverse tensile modulus E22, unidirectional lamina, 22 °C, dry, high strain rate
    value: 11.9
    unit: GPa
    scope: material
    conditions:
      orientation: transverse (90 degree)
      form: unidirectional AS4/3501-6 graphite/epoxy, not the 8H fabric
      temperature: 22 °C (72 °F)
      moisture: 0 %
      strain_rate: high
    method: Average transverse tensile modulus as printed in NASA CR-187229 Table 5.1
    status: ground
    source: nasa-cr-187229
    where: Table 5.1, Average transverse tensile properties, Transverse Modulus E22 row, High strain rate, 0% moisture 22 C column (printed as 11.9 GPa with 1.73 Msi)
  - benchmark: elastic_modulus
    label: Transverse tensile modulus E22, unidirectional lamina, 22 °C, dry, low strain rate
    value: 10
    unit: GPa
    scope: material
    conditions:
      orientation: transverse (90 degree)
      form: unidirectional AS4/3501-6 graphite/epoxy, not the 8H fabric
      temperature: 22 °C (72 °F)
      moisture: 0 %
      strain_rate: low
    method: Average transverse tensile modulus as printed in NASA CR-187229 Table 5.1
    status: ground
    source: nasa-cr-187229
    where: Table 5.1, Average transverse tensile properties, Transverse Modulus E22 row, Low strain rate, 0% moisture 22 C column (printed as 10.0 GPa with 1.45 Msi)
  - benchmark: moisture_absorption
    label: Equilibrium moisture content, [90s] unidirectional specimen, in water at 49 °C
    value: 1.41
    unit: '%'
    scope: material
    conditions:
      orientation: '[90s] unidirectional'
      form: unidirectional AS4/3501-6 graphite/epoxy
      environment: immersion in water at 49 °C (120 °F)
      basis: equilibrium value as stated by the report; the report says the absorption curves had not reached equilibrium in its test
    method: Moisture weight gain of the embedded-gauge specimen, reported as equilibrium moisture content in NASA CR-187229 section 5.1.1
    status: ground
    source: nasa-cr-187229
    where: Section 5.1.1, Moisture Absorption Evaluation Results, text for the [90s] specimen (equilibrium moisture content of 1.41 %), Figure 5.2 data
  - benchmark: moisture_absorption
    label: Equilibrium moisture content, [0s] unidirectional specimen, in water at 49 °C
    value: 1.34
    unit: '%'
    scope: material
    conditions:
      orientation: '[0s] unidirectional'
      form: unidirectional AS4/3501-6 graphite/epoxy
      environment: immersion in water at 49 °C (120 °F)
      basis: equilibrium value as stated by the report; the report says the absorption curves had not reached equilibrium in its test
    method: Moisture weight gain of the embedded-gauge specimen, reported as equilibrium moisture content in NASA CR-187229 section 5.1.1
    status: ground
    source: nasa-cr-187229
    where: Section 5.1.1, Moisture Absorption Evaluation Results, text for the [0s] specimen (equilibrium moisture content of 1.34%), Figure 5.2 data
corrosion:
  - environment: 'Moist heat: 180 °F and 93% relative humidity (the test-coupon conditioning the NASA report used)'
    headline: Moisture lowers the glass transition temperature of AS4/3501-6, mostly within the first 10 days of exposure at 180 °F and 93% RH.
    effect: The NASA report says the major loss in Tg occurs in the first 10 days at 180 °F and 93% RH, and that Tg begins to plateau after about 20 days. The Tg values for the conditioned laminate are shown in the report figures only. The unconditioned dry Tg was 398 °F by DMA. The report says all AS4/3501-6 test coupons were conditioned for 10 days at 180 °F and 93% RH, and that this exposure was sufficient.
    rating: moderate
    conditions:
      exposure: 180 °F and 93% relative humidity
      time: 10 days (major Tg loss) to about 20 days (plateau), per the report text
      laminate: six-ply composite for the Tg-versus-time test
    source: nasa-tm-2000-210252
    where: Section 2.3 (Moisture Conditioning), Tg paragraph and Figure 4; Section 6 (Conclusions)
  - environment: Moisture uptake at 180 °F and 93% RH (predicted 10-day soak)
    headline: The report predicts a 10-day soak at 180 °F and 93% RH gives 0.9%, 0.75% and 0.6% moisture gain for 6-, 8- and 10-ply laminates.
    effect: These weight gains are predicted from a diffusion model and checked against conditioned test specimens. The report says the measured weight gains matched the predicted gains, and that beach exposure panels gained less weight than the test specimens.
    rating: moderate
    conditions:
      exposure: 180 °F and 93% relative humidity
      time: 10 days
      laminates: 6-, 8- and 10-ply AS4/3501-6, values as printed
      basis: predicted in the report from the diffusion model (printed as should result in)
    source: nasa-tm-2000-210252
    where: Section 2.3 (Moisture Conditioning), paragraph after Figure 6; Section 6 (Conclusions)
risks:
  hazards:
    - text: The Hexcel AS4 product data sheet tells users to obtain, read and understand the safety data sheet before use. No safety data sheet for AS4/3501-6 was read for this profile, so no GHS or hazard classification is stated here.
      source: hexcel-as4-datasheet
      where: Safety Information section
  failure_risks:
    - mode: Loss of glass transition temperature after moisture uptake
      trigger: Exposure to 180 °F and 93% relative humidity
      consequence: Tg falls with moisture uptake, with most of the loss in the first 10 days, so the usable high-temperature limit drops. The report says the moisture-conditioned composite would also change with exposure time at 600 °F, which is well above the Tg.
      severity: moderate
      source: nasa-tm-2000-210252
      where: Section 2.3 (Moisture Conditioning) and the discussion of baking at 600 °F in Section 4
    - mode: Fibre misalignment in fabrication
      trigger: Lot 2 prepreg, identified during tensile testing
      consequence: Some specimens had fill misalignment as high as 6 degrees on as many as half the plies. This misalignment affected the high-temperature tensile fill results and gave large scatter in strength and modulus between panels.
      severity: moderate
      source: nasa-tm-2000-210252
      where: Section 5 (Test Results), first paragraph
    - mode: Moisture lowers transverse tensile strength of unidirectional AS4/3501-6
      trigger: 1% moisture content at 22 °C (72 °F), high strain rate
      consequence: In NASA CR-187229 Table 5.1, high strain rate transverse tensile strength at 22 °C fell from 59.3 MPa at 0% moisture to 40.8 MPa at 1% moisture. The unidirectional tape values are kept separate from the 8H fabric values.
      severity: moderate
      source: nasa-cr-187229
      where: Table 5.1, Average transverse tensile properties for unidirectional AS4/3501-6
    - mode: Notch sensitivity of tape laminates
      trigger: Open-hole tension on the multi-angle tape laminates tested, with one hole size
      consequence: NASA CR-4610 states that the tape laminates showed some notch sensitivity. Table 3.1 gives unnotched and open-hole tension strengths for the laminate layups, which are not the 8H fabric in the rows above.
      severity: moderate
      source: nasa-cr-4610
      where: Section 3 (tension) text on notch sensitivity, and Table 3.1 Laminate Longitudinal Tension Properties
    - mode: Delamination from low through-thickness strength
      trigger: Geometric or material discontinuities in the laminate, and impact (Figure 2 is a compression-after-impact result)
      consequence: NASA/TM-2010-216869 states that composites have low through-thickness strength, so delaminations can start and grow, and that delaminations degrade the strength of the laminate. Its Figure 2 gives compression-after-impact strength for AS4/3501-6 from NASA Langley test data.
      severity: moderate
      source: nasa-tm-2010-216869
      where: Body text on delamination, and the Figure 2 caption naming AS4/3501-6
  handling:
    - text: Condition wet test coupons at 180 °F and 93% RH for 10 days. The NASA report found this exposure sufficient for the moisture absorption of the composite.
      source: nasa-tm-2000-210252
      where: Section 6 (Conclusions)
    - text: For spacecraft use, screen the laminate in vacuum outgassing. NASA's outgassing database reports total mass loss and collected volatile condensable material from the ASTM E 595 test. No AS4/3501-6 record was read in this run.
      source: nasa-outgassing-guide
      where: User guide, description of the test method and of the database sections
  mitigations:
    - text: 'The report notes that the Hypalon coating tried as a moisture barrier was ineffective: the coated specimens gained about the same moisture as the uncoated composite. Material properties therefore had to be developed in the wet state.'
      source: nasa-tm-2000-210252
      where: Section 2.3 (Moisture Conditioning)
uses:
  - application: structures
    device: Space Shuttle solid rocket booster composite nose cap (NASA and USBI development, to replace a metallic TPS-coated nose cap)
    example: Two facesheets of AS4/3501-6 graphite/epoxy encapsulate a core of Scotch-Core SC350G syntactic foam, cocured in an autoclave for 4 hr at 375 °F and 85 psig.
    source: nasa-tm-2000-210252
    where: Section 1 (Introduction) and Section 2.1 (Materials and Processing)
  - application: structures
    device: Woven, prepregged, wound or braided composite parts made from HexTow AS4 fibre (general product use)
    example: Hexcel suggests HexTow AS4 for weaving, prepregging, filament winding, braiding and pultrusion. This is the fibre product use, not a use specific to the 3501-6 resin.
    source: hexcel-as4-datasheet
    where: Product description paragraph, first page
supply:
  - subject: PAN-based carbon fibre (AS4 tow)
    abundance: 'Not applicable: a synthetic fibre made from a polyacrylonitrile (PAN) precursor, so no crustal abundance applies'
    producers: []
    manufacture: Hexcel says it manufactures high performance carbon fibre from PAN precursor. The FY2024 10-K also says Hexcel resumed construction of a new carbon fiber line in Decatur, AL, and names Salt Lake City, Utah as the site adjacent to its existing carbon fibre and prepreg operations. No production shares by country were read in a fetched source. The Hexcel AS4 datasheet names the manufacturer and the certification specification HS-CP-5000.
    critical_lists: []
    recycling: Not found in the sources read for this profile.
    substitutes: []
    source: hexcel-10k-fy2024
    where: Item 1 Business, Raw Materials and Production Activities; Research and Technology, Patents and Know-How (Salt Lake City sentence)
  - subject: Acrylonitrile (primary raw material for the PAN precursor)
    abundance: Not found in the sources read for this profile.
    producers: []
    manufacture: The 10-K says the primary raw material for PAN is acrylonitrile, and that many key raw materials are available from relatively few sources. It gives no supplier count or share.
    critical_lists: []
    recycling: Not found in the sources read for this profile.
    substitutes: []
    source: hexcel-10k-fy2024
    where: Item 1 Business, Raw Materials and Production Activities
documents:
  - title: Mechanical Property Allowables Generated for the Solid Rocket Booster Composite Nose Cap (NASA/TM-2000-210252)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20000060843/downloads/20000060843.pdf
    year: 2000
  - title: HexTow AS4 Carbon Fiber Product Data Sheet (Hexcel, March 2010), copy hosted by Rockwest Composites
    type: datasheet
    url: https://www.rockwestcomposites.com/on/demandware.static/Sites-RWC-Site/Sites-rwc-master-catalog/-/wysiwyg/AS4.pdf
    year: 2010
  - title: Hexcel Corporation Form 10-K for fiscal year 2024 (SEC filing)
    type: report
    url: https://www.sec.gov/Archives/edgar/data/717605/000095017025014412/hxl-20241231.htm
    year: 2025
  - title: Environmental and Strain Rate Effects on Graphite/Epoxy Composites (NASA CR-187229)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19920011242/downloads/19920011242.pdf
    year: 1991
  - title: A Comparison of Graphite/Epoxy Tape Laminates and 2-D Braided Composites, Mechanical Properties (NASA CR-4610)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19940033071/downloads/19940033071.pdf
    year: 1994
  - title: Comparison of Requirements for Composite Structures for Aircraft and Space Applications (NASA/TM-2010-216869)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20110003478/downloads/20110003478.pdf
    year: 2010
gaps:
  - No composite density, resin density or laminate CTE for AS4/3501-6 was found in the sources read for this profile. Only the fibre density and CTE were found.
  - No 3501-6 resin datasheet from Hexcel was found. A reseller page (Knowde) gave Tg figures and an amine-cure description in a search result, but the page could not be read in this run, so none of those values are used here.
  - No cure schedule for the 3501-6 resin alone was found. The only cure cycle is the NASA nose-cap cocure (4 hr at 375 °F, 85 psig), which is for a sandwich.
  - No UV, atomic oxygen, outgassing, vacuum or low Earth orbit test result for AS4/3501-6 was found in the sources read. The NASA report has no space-environment data.
  - No flight data beyond the Space Shuttle SRB nose cap development was found in the sources read. The report describes development and ground testing, not flight results.
  - No safety data sheet for AS4 or 3501-6 was read. The Hexcel SDS result found in search covers a sized HexTow family that is not AS4-specific, so it was not used.
  - No CAS number, UNS, EN or other designation for AS4/3501-6 or the 3501-6 resin was printed in the sources read.
  - Compressive strength, in-plane shear strength, interlaminar shear strength and compressive modulus are not in the property canon. They are stored under snake_case names (compressive_strength, in_plane_shear_strength, interlaminar_shear_strength, compressive_modulus) and need a canon entry or a mapping at import.
  - The fill compressive strength and modulus at 75 °F and 240 °F in Table 6 are not used, because the scan text was ambiguous and the numbers were not clearly readable in the rendered page.
  - The Tg-versus-moisture curve is shown only in report figures, which were not read as numbers. NASA CR-187229 reports equilibrium moisture content for unidirectional specimens, but says its absorption curves had not reached equilibrium, so those values are used with that caveat. No Tg value at moisture equilibrium was found. Transverse values from CR-187229 are for unidirectional tape, so they are kept apart from the fabric values.
  - The Rockwest AS4 sheet also prints HexPly 8552 composite values (0-degree tensile 320 ksi, etc.). These are for a different resin, so they are not used for AS4/3501-6.
  - Eight sources are cited. The Hexcel AS4D datasheet was fetched but not used, because the AS4D is a 12K fibre with different strength values. A NASA textile-composite ageing paper was fetched but not used, because it covers AS4/E905L rather than AS4/3501-6. A NASA LDEF surface study was read but not used, because it does not name AS4/3501-6.
  - No producer share by country and no critical-mineral listing was found for PAN-based carbon fibre or the 3501-6 resin. The Hexcel FY2024 10-K names Hexcel as the carbon fibre maker and acrylonitrile as the PAN raw material, without shares.
  - The NASA outgassing database itself was not queried for this grade. Only its user guide was read, so the TML and CVCM outgassing values for AS4/3501-6 are unquantified.
  - No uses beyond the SRB composite nose cap and general AS4 fibre processing were found for 3501-6 in the sources read.
  - Hazard and handling data beyond the Hexcel sentence telling users to read the SDS were not found in the sources read for this profile.
  - The Wikipedia article is used only for the composition sentence (carbon fibre reinforcement in a polymer matrix, usually epoxy). It gives no numeric value, and its history lines are not used.
license: CC-BY-4.0
sources:
  nasa-tm-2000-210252:
    title: Mechanical Property Allowables Generated for the Solid Rocket Booster Composite Nose Cap (NASA/TM-2000-210252)
    id: NASA/TM-2000-210252 (A.J. Hodge, Marshall Space Flight Center, May 2000)
    url: https://ntrs.nasa.gov/api/citations/20000060843/downloads/20000060843.pdf
    year: 2000
    kind: report
    license: public domain (NASA)
  hexcel-as4-datasheet:
    title: HexTow AS4 Carbon Fiber Product Data Sheet (Hexcel Corporation, March 2010), copy hosted by Rockwest Composites
    id: Hexcel HexTow AS4 Product Data, March 2010
    url: https://www.rockwestcomposites.com/on/demandware.static/Sites-RWC-Site/Sites-rwc-master-catalog/-/wysiwyg/AS4.pdf
    year: 2010
    kind: datasheet
    license: supplier document, linked not reproduced
  hexcel-10k-fy2024:
    title: Hexcel Corporation Form 10-K for fiscal year 2024 (SEC filing)
    id: SEC EDGAR filing for CIK 717605, accession 0000950170-25-014412
    url: https://www.sec.gov/Archives/edgar/data/717605/000095017025014412/hxl-20241231.htm
    year: 2025
    kind: report
    license: public SEC filing
  nasa-cr-187229:
    title: Environmental and Strain Rate Effects on Graphite/Epoxy Composites (NASA CR-187229)
    id: NASA CR-187229, Konstantinos Peimandis, Northwestern University, October 1991 (NTRS 19920011242)
    url: https://ntrs.nasa.gov/api/citations/19920011242/downloads/19920011242.pdf
    year: 1991
    kind: report
    license: public domain (NASA)
  nasa-cr-4610:
    title: A Comparison of Graphite/Epoxy Tape Laminates and 2-D Braided Composites, Mechanical Properties (NASA CR-4610)
    id: NASA CR-4610, Pierre J. Minguet and Christian K. Gunther, Boeing Defense and Space Group, July 1994 (NTRS 19940033071)
    url: https://ntrs.nasa.gov/api/citations/19940033071/downloads/19940033071.pdf
    year: 1994
    kind: report
    license: public domain (NASA)
  nasa-tm-2010-216869:
    title: Comparison of Requirements for Composite Structures for Aircraft and Space Applications (NASA/TM-2010-216869)
    id: NASA/TM-2010-216869, Ivatury S. Raju and co-authors, NASA Langley Research Center, December 2010 (NTRS 20110003478)
    url: https://ntrs.nasa.gov/api/citations/20110003478/downloads/20110003478.pdf
    year: 2010
    kind: report
    license: public domain (NASA)
  nasa-outgassing-guide:
    title: NASA Outgassing Database User Guide (NASA Goddard Space Flight Center)
    id: NASA GSFC outgassing database user guide
    url: https://etd.gsfc.nasa.gov/capabilities/outgassing-database/user-guide/
    kind: web
    license: public domain (NASA)
  wikipedia-cfrp:
    title: Carbon fiber reinforced polymer (Wikipedia)
    id: Wikipedia article Carbon_fiber-reinforced_polymer
    url: https://en.wikipedia.org/wiki/Carbon_fiber-reinforced_polymer
    kind: web
    license: CC BY-SA 4.0 (linked, not reproduced)
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 35
  unreachable: 0
  caveats: 3
  note: Written by an AI assistant on 2026-11-01 from the NASA TM 2000-210252 report (Table 6 read from the rendered page) and the Rockwest copy of the Hexcel AS4 datasheet. Eight sources cited, including NASA CR-187229 (unidirectional transverse and moisture values), NASA CR-4610 (notch sensitivity), NASA/TM-2010-216869 (delamination), the Hexcel FY2024 10-K (supply) and the NASA outgassing user guide (test method only). The Hexcel AS4D datasheet was fetched but not used for values.
story:
  recipe:
    line: AS4/3501-6 is a graphite/epoxy composite. Its reinforcement is Hexcel AS4, a PAN-based carbon fibre woven as 8-harness satin fabric from 3K tows, and its matrix is a 3501-6 epoxy resin. In the NASA nose cap the laminate was cocured in an autoclave for 4 hr at 375 °F and 85 psig, with a ramp of 2 to 3 °F per minute and cooling of 1 to 2 °F per minute.
    parts:
      - name: Carbon fibre (AS4, PAN-based)
        symbol: C
        share: 94.0% carbon content of the fibre, per the Hexcel AS4 datasheet
        role: Carries the load. The fibre sets the tensile strength and stiffness of the laminate in the fibre direction.
      - name: 3501-6 epoxy resin
        share: Fibre volume of the laminate is 59.9 to 62.7% (NASA acid digestion); the rest is resin
        role: Holds the fibres together, transfers load between them and sets the glass transition temperature (about 380 to 398 °F in the NASA tests).
  risk_groups:
    - title: For people
      level: 0
      verdict: No hazard classification found in the sources read
      lead: No safety data sheet for AS4/3501-6 was read, so this profile does not give a hazard classification. The Hexcel AS4 datasheet tells users to read the safety data sheet before use.
      points:
        - label: Before use
          line: Read the supplier safety data sheet for the exact prepreg or fibre before handling. The NASA report does not list hazard data for the resin.
    - title: If the laminate overheats or stays wet
      lead: These effects come from the NASA material tests, not from incidents.
      points:
        - label: Moisture
          line: At 180 °F and 93% relative humidity the glass transition temperature falls, mostly in the first 10 days. The dry value is 398 °F by DMA and the unconditioned value is 386 °F by DMA.
        - label: Above the glass transition
          line: The NASA report says a moisture-conditioned laminate would change with exposure time at 600 °F, which is well above the glass transition temperature.
    - title: Handling and storage
      points:
        - label: Coupon conditioning
          line: NASA conditioned all wet test coupons at 180 °F and 93% relative humidity for 10 days, and found this sufficient for the moisture absorption of the composite.
        - label: Fabrication
          line: In the NASA lot 2 prepreg, fibre misalignment as high as 6 degrees on as many as half the plies gave large scatter in high-temperature fill tensile results.
  why: Hexcel AS4/3501-6 is a graphite/epoxy composite with a long record in US space hardware. It is the material NASA Marshall chose for the facesheets of the Space Shuttle solid rocket booster composite nose cap, a sandwich with a syntactic foam core. The nose cap was developed to replace a metallic nose cap coated with thermal protection. The report calls the composite's strength-to-weight advantage and the removal of a debris hazard the reasons for the change. The properties below are the lamina values NASA printed for the 8H fabric and the fibre values from the Hexcel datasheet.
  uses:
    - where: Space Shuttle SRB composite nose cap
      line: NASA and USBI built a composite nose cap for the Space Shuttle solid rocket booster, a sandwich of two AS4/3501-6 facesheets around a SC350G syntactic foam core. The report says the composite sandwich structure removes the thermal protection system that the metallic nose cap needed.
    - where: Composite parts made from AS4 fibre
      line: Hexcel suggests HexTow AS4 for weaving, prepregging, filament winding, braiding and pultrusion. This describes the fibre product, not the 3501-6 resin specifically.
  can_do:
    - label: Warp tensile strength
      benchmark: ultimate_tensile_strength
      value: 111.6 ksi
      line: At 75 °F the average warp tensile strength of the 8H AS4/3501-6 lamina was 111.6 ksi, and the A-basis value was 98.0 ksi, per NASA Table 6.
    - label: Warp tensile strength at 350 °F
      benchmark: ultimate_tensile_strength
      value: 93.9 ksi
      line: After samples were heated to 600 °F and cooled to 350 °F, the average warp tensile strength was 93.9 ksi, per NASA Table 6.
    - label: Glass transition
      benchmark: glass_transition_temperature
      value: 386 °F
      line: The unconditioned laminate had a glass transition temperature of 386 °F by DMA and 380 °F by DSC. A dry sample measured 398 °F by DMA, per NASA Section 2.3.
    - label: Fibre strength
      benchmark: ultimate_tensile_strength
      value: 4433 MPa
      line: The AS4 carbon fibre tow has a typical tensile strength of 4,433 MPa (643 ksi), per the Hexcel AS4 datasheet. This is a fibre value, not a laminate value.
  compare: NASA CR-4610 (1994) compares AS4/3501-6 unidirectional tape laminates with 2-D braided composites. It reports that the braided material had a severe unnotched transverse strength reduction compared with the tape laminates, and that the braids showed no notch sensitivity at the single hole size tested. The NASA nose cap report compares the composite with the metallic nose cap it replaced only in terms of strength-to-weight and debris. The lamina values above are the basis for the compare table, which uses the same measurement names as the other profiles.
  compare_rows:
    - label: Warp tensile strength
      75 °F average: null
      benchmark: ultimate_tensile_strength
    - label: Glass transition
      DMA unconditioned: null
      benchmark: glass_transition_temperature
    - label: Warp tensile modulus
      75 °F average: null
      benchmark: elastic_modulus
  handling:
    - Read the supplier safety data sheet before handling. No hazard classification for AS4/3501-6 was found in the sources read.
    - Keep moisture out of the laminate. Moisture lowers the glass transition temperature, mostly in the first 10 days at 180 °F and 93% RH.
    - For wet test coupons, use the NASA conditioning of 10 days at 180 °F and 93% RH.
  good_for:
    - Flight-heritage structural laminates. NASA used it for the facesheets of the Space Shuttle solid rocket booster composite nose cap.
    - Strength at moderate temperature. The warp tensile strength is 111.6 ksi at 75 °F and 93.9 ksi at 350 °F after a 600 °F excursion, per NASA Table 6.
  watch_out:
    - Moisture. The glass transition temperature falls with moisture uptake, mostly in the first 10 days at 180 °F and 93% RH.
    - High temperature. Warp tensile strength falls to 74.8 ksi at 550 °F and to 74.6 ksi at 480 °F (warp, average), per NASA Table 6.
    - Fibre misalignment in fabrication. The NASA report saw up to 6 degrees of fill misalignment in lot 2 prepreg.
    - Notches and transverse loads. NASA CR-4610 reports that tape laminates show some notch sensitivity. NASA CR-187229 Table 5.1 shows transverse tensile strength falling with 1% moisture.
  verdict: AS4/3501-6 is a well-documented ground-test laminate with NASA lamina data at temperatures from 75 °F to 550 °F. The sources read here do not cover space-environment exposure or resin-level data, so those gaps should be closed before it is used beyond the nose-cap heritage.