Carbon-fibre reinforced epoxy (CFRP) CFRP

spore: profile
id: cfrp
spore_version: 0.2
family: glass-and-composites
name: Carbon-fibre reinforced epoxy (CFRP)
abbreviation: CFRP
role: structural composite
category: composites
type: carbon-fiber-reinforced
summary: |
  Carbon-fibre reinforced polymer is carbon fibre tows or fabric set in an epoxy matrix and cured into a laminate. The Hexcel HexPly 8552 prepreg with IM7 fibre is a 350 F cure, toughened epoxy system used in space launchers and space structures. Its unidirectional laminate reaches 2724 MPa tensile strength at 0 degrees (dry, 25 C), while a quasi-isotropic 25/50/25 layup gives 717 MPa.
best_for: 'Stiffness and strength per unit mass in structures: 164 GPa at 0 degrees in unidirectional IM7/8552 laminate'
weakest_at: 'Strength across the fibres: 64 MPa at 90 degrees in unidirectional IM7/8552, and the epoxy limits service to about 121 C'
identity:
  formula: Carbon fibre (T700S or IM7 tows) in an amine-cured toughened epoxy matrix; the example system is Hexcel HexPly 8552 (IM7 fibre), a prepreg with 33 to 38 % resin content for tapes
  source: hexcel-8552
  where: Description section and Typical Physical Properties table of the HexPly 8552 Product Data Sheet
  resin_content: 33-38 % by mass, printed for the HexPly 8552 prepreg (Typical Physical Properties table, % Resin Content row)
  fibre_content_computed: 62-67 % by mass, computed as 100 minus the printed 33-38 % resin content
tags:
  environments:
    - low-earth-orbit
  stresses:
    - thermal-cycling
    - vacuum-and-outgassing
  applications:
    - structures
    - habitats-and-suits
    - propulsion-and-tanks
properties:
  - benchmark: density
    label: Density of neat HexPly 8552 epoxy resin
    value: 1.3
    unit: g/cm3
    scope: material
    conditions:
      form: unreinforced 8552 resin
      temperature: not stated
    method: Value printed in a manufacturer datasheet, converted from 0.0470 lb/in3 (factor 27.68)
    status: ground
    source: hexcel-8552
    where: Neat Resin Properties, row Density
  - benchmark: max_service_temp
    label: Service temperature of HexPly 8552 composites
    value: 121
    unit: °C
    scope: material
    conditions:
      unit_in_source: 250 °F
      basis: stated service limit of the matrix system
    method: Service limit printed in a manufacturer datasheet, converted from 250 °F
    status: ground
    source: hexcel-8552
    where: Features list, first bullet
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 0 degrees, IM7/8552 unidirectional
    value: 2724
    unit: MPa
    scope: material
    conditions:
      fibre: IM7
      matrix: HexPly 8552
      layup: unidirectional, 0 degrees
      temperature: 77 F (25 C)
      state: dry
      unit_in_source: 395 ksi
    method: Typical value printed in a manufacturer datasheet (mechanical properties table), converted from 395 ksi (factor 6.894757)
    status: ground
    source: hexcel-8552
    where: Mechanical Properties table, row 0 degrees Tensile strength, ksi, 77 Dry, IM7 column
  - benchmark: elastic_modulus
    label: Tensile modulus at 0 degrees, IM7/8552 unidirectional
    value: 164
    unit: GPa
    scope: material
    conditions:
      fibre: IM7
      matrix: HexPly 8552
      layup: unidirectional, 0 degrees
      temperature: 77 F (25 C)
      state: dry
      unit_in_source: 23.8 msi
    method: Typical value printed in a manufacturer datasheet, converted from 23.8 msi (factor 6.894757)
    status: ground
    source: hexcel-8552
    where: Mechanical Properties table, row 0 degrees Tensile modulus, msi, 77 Dry, IM7 column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 90 degrees, IM7/8552 unidirectional
    value: 64
    unit: MPa
    scope: material
    conditions:
      fibre: IM7
      matrix: HexPly 8552
      layup: unidirectional, 90 degrees
      temperature: 77 F (25 C)
      state: dry
      unit_in_source: 9.3 ksi
    method: Typical value printed in a manufacturer datasheet, converted from 9.3 ksi (factor 6.894757)
    status: ground
    source: hexcel-8552
    where: Mechanical Properties table, row 90 degrees Tensile strength, ksi, 77 Dry, IM7 column
  - benchmark: elastic_modulus
    label: Tensile modulus at 90 degrees, IM7/8552 unidirectional
    value: 11.7
    unit: GPa
    scope: material
    conditions:
      fibre: IM7
      matrix: HexPly 8552
      layup: unidirectional, 90 degrees
      temperature: 77 F (25 C)
      state: dry
      unit_in_source: 1.70 msi
    method: Typical value printed in a manufacturer datasheet, converted from 1.70 msi (factor 6.894757)
    status: ground
    source: hexcel-8552
    where: Mechanical Properties table, row 90 degrees Tensile modulus, msi, 77 Dry, IM7 column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, quasi-isotropic 25/50/25 laminate, IM7/8552
    value: 717
    unit: MPa
    scope: material
    conditions:
      fibre: IM7
      matrix: HexPly 8552
      layup: quasi-isotropic 25/50/25
      temperature: 77 F (25 C)
      state: dry
      unit_in_source: 104 ksi
    method: Typical value printed in a manufacturer datasheet, converted from 104 ksi (factor 6.894757)
    status: ground
    source: hexcel-8552
    where: Mechanical Properties table, Quasi-Isotropic 25/50/25 block, row Tensile strength, IM7 column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, T700S carbon fibre (single fibre)
    value: 4900
    unit: MPa
    scope: material
    conditions:
      fibre: T700S, standard modulus, 12k and 24k tows
      layup: not applicable (fibre property)
      temperature: room temperature (not stated)
      unit_in_source: 500 kgf/mm2
    method: Nominal value printed in a manufacturer fibre data sheet (test method TY-QA-002)
    status: ground
    source: toray-t700s
    where: Fibre properties table, row Tensile Strength, Nominal value
  - benchmark: elastic_modulus
    label: Tensile modulus, T700S carbon fibre
    value: 230
    unit: GPa
    scope: material
    conditions:
      fibre: T700S
      layup: not applicable (fibre property)
      unit_in_source: 23.5 kgf/mm2 x 10^3
    method: Nominal value printed in a manufacturer fibre data sheet (test method TY-QA-002)
    status: ground
    source: toray-t700s
    where: Fibre properties table, row Tensile Modulus, Nominal value
  - benchmark: density
    label: Density, T700S carbon fibre
    value: 1.8
    unit: g/cm3
    scope: material
    conditions:
      fibre: T700S
      temperature: not stated
    method: Nominal value printed in a manufacturer fibre data sheet (test method TY-QA-003)
    status: ground
    source: toray-t700s
    where: Fibre properties table, row Density
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, T700S in a Toray 2500 epoxy composite
    value: 2550
    unit: MPa
    scope: material
    conditions:
      fibre: T700S
      matrix: Toray 2500, cure 120 C
      layup: not stated in the datasheet
      fibre_volume: 60 % (normalized)
      temperature: room temperature
      unit_in_source: 260 kgf/mm2
    method: Nominal value printed in a manufacturer composite-property table
    status: ground
    source: toray-t700s
    where: Composite properties table, row Tensile Strength, footnote "Toray 2500 - 120 C resin system, normalized to 60 % fiber volume"
  - benchmark: elastic_modulus
    label: Tensile modulus, T700S in a Toray 2500 epoxy composite
    value: 135
    unit: GPa
    scope: material
    conditions:
      fibre: T700S
      matrix: Toray 2500, cure 120 C
      layup: not stated in the datasheet
      fibre_volume: 60 % (normalized)
      temperature: room temperature
    method: Nominal value printed in a manufacturer composite-property table
    status: ground
    source: toray-t700s
    where: Composite properties table, row Tensile Modulus, footnote as above
  - benchmark: moisture_absorption
    label: Water uptake of adhesive-bonded T800H/3900-2 composite joints after ageing
    value: 0.75
    unit: '%'
    scope: material
    conditions:
      form: single lap-shear specimens bonded from T800H/3900-2 prepreg panels
      ageing: 71 C and 85 % relative humidity
      duration: 360 days
      control: stored at about 20 % relative humidity, little to no weight change
    method: Weight gain printed in the text after 360 days of ageing; mass measured on removal from the chamber. This is a bonded joint, not a laminate, so it is not a laminate saturation value.
    status: ground
    source: palmieri-2013
    where: Results, paragraph on the aged lap-shear specimens after 360 days
  - benchmark: cte
    label: Coefficient of thermal expansion, graphite-epoxy coupons, layup 0/30/90/-30
    value: 0.18
    unit: ppm/K
    scope: material
    conditions:
      form: graphite-epoxy coupons, specimen set P45 987
      layup: '[0, 30, 90, -30] as printed in the report text (garbled in the extracted text)'
      temperature: not stated in the table
      unit_in_source: 10-6/C
      matrix: not named in the report table
    method: Average of six coupon results printed in Table 3 of the report. The text says a correction factor of 0.9 ppm/C is added to raw laser-dilatometer readings to give the final result; the table is read here as the final value.
    status: ground
    source: nasa-tm104637
    where: Table 3 (continued), P45 987 coupons, Average CTE row
  - benchmark: total_mass_loss
    label: Total mass loss in vacuum, AS-4/1908 epoxy/graphite laminate
    value: 0.11
    unit: '%'
    scope: material
    conditions:
      sample: laminate, ID GSC10245, manufacturer HER
      cure: 2H (as printed in the database)
      test: total mass loss in vacuum, per the NASA outgassing database
    method: Value read from the NASA outgassing database. The CSV prints no unit row, so percent of initial mass is assumed (the ASTM E595 convention used in NASA TM 104637). Not a value for the HexPly 8552 or T700S systems.
    status: ground
    source: nasa-outgassing-db
    where: Row LAMINATE AS-4/1908 EPOXY/GRAPHITE (GSC10245), column TML
  - benchmark: total_mass_loss
    label: Total mass loss in vacuum, CYCOM 985-T300 graphite/epoxy
    value: 0.57
    unit: '%'
    scope: material
    conditions:
      sample: structural, ID GSC12224, manufacturer ACC
      cure: 1H (as printed in the database)
      test: total mass loss in vacuum, per the NASA outgassing database
    method: Value read from the NASA outgassing database. No unit row in the CSV; percent assumed. Different resin system from HexPly 8552.
    status: ground
    source: nasa-outgassing-db
    where: Row CYCOM 985-T300 GRAPHITE/EPOXY (GSC12224), column TML
  - benchmark: total_mass_loss
    label: Total mass loss in vacuum, carbon fibre epoxy laminate T300/M76
    value: 0.6
    unit: '%'
    scope: material
    conditions:
      sample: laminate, ID GSC28291, manufacturer HEC
      cure: 4H (as printed in the database)
      test: total mass loss in vacuum, per the NASA outgassing database
    method: Value read from the NASA outgassing database. No unit row in the CSV; percent assumed. Different resin system from HexPly 8552.
    status: ground
    source: nasa-outgassing-db
    where: Row CARBON FIBER EPOXY LAMINATE T300/M76 (GSC28291), column TML
corrosion:
  - environment: Aluminium 7075 coupled to CFRP in 3.5 wt% NaCl
    headline: Coupling aluminium to CFRP drives galvanic corrosion of the aluminium; the aluminium acts as the anode.
    effect: In the coupled test the Al 7075 served as the anode, with accelerated dissolution at the interface. The paper says galvanic corrosion at the joint interfaces accelerates adhesive failure and strength damage.
    rating: severe
    conditions:
      electrolyte: 3.5 wt% NaCl
      couple: Al 7075 in contact with CFRP
      test: galvanic coupling for 120 min, galvanic current density recorded
    source: sci-rep-2022-galvanic
    where: Abstract; Results, galvanic current density and Fig. 1
  - environment: Al 7075 with plasma electrolytic oxidation (PEO) coating, coupled to CFRP in 3.5 wt% NaCl
    headline: A PEO coating cut the galvanic current density by about 90 % over 120 min.
    effect: The PEO-600 and PEO-700 coatings reduced galvanic current density by about 90 % against the uncoated Al-alloy/CFRP coupling and about 88 % against thin film sulphuric acid anodizing, averaged over 120 min. The paper calls this a promising protection for practical use; it is a laboratory coupon test.
    rating: low
    conditions:
      electrolyte: 3.5 wt% NaCl
      method: galvanic current density over 120 min
    source: sci-rep-2022-galvanic
    where: Results text on galvanic current density after 120 min
  - environment: Hot, wet ageing of bonded CFRP joints at 71 C and 85 % relative humidity
    headline: Bonded T800H/3900-2 joints gained about 0.75 % water and lost about 27 % of their apparent shear strength in 360 days.
    effect: Control specimens showed little or no weight change. Aged apparent shear strength was 27.0 MPa against 36.6 MPa for controls. Failures stayed mostly cohesive.
    rating: moderate
    conditions:
      temperature: 71 C
      humidity: 85 % relative humidity
      duration: 360 days
      specimen: single lap-shear bonded joints, not laminates
    source: palmieri-2013
    where: Results, aged lap-shear specimens after 360 days
  - environment: Moisture at elevated temperature in epoxy laminates
    headline: Absorbed water softens the epoxy and lowers its glass transition temperature.
    effect: The report says absorbed water softens epoxy resins, causes them to swell and lowers their glass transition temperature. No numeric shift for the HexPly 8552 resin was read in this run.
    rating: moderate
    conditions:
      basis: qualitative statement from a graphite/epoxy study with 0 % and 1 % moisture test conditions
    source: nasa-cr187229
    where: Introduction, paragraph on absorbed moisture
uses:
  - application: structures
    device: Space launcher structures
    example: Hexcel lists HexPly 8552 for space launchers, with space and defense aircraft structures among its applications.
    source: hexcel-8552
    where: Applications list at the top of the Product Data Sheet (Space Launchers; Space and Defense)
  - application: structures
    device: Primary and secondary aircraft structures
    example: The HexPly 8552 Product Data Sheet lists primary and secondary aircraft structures among its commercial aerospace applications.
    source: hexcel-8552
    where: Applications list at the top of the Product Data Sheet (Commercial Aerospace)
  - application: optics-and-cameras
    device: Prototype optical bench of graphite-epoxy
    example: NASA Goddard used a laser dilatometer to measure the CTE of graphite-epoxy structures, which allowed loading and thermal expansion tests on a prototype optical bench.
    source: nasa-tm104637
    where: Section I, summary
  - application: structures
    device: Al-alloy/CFRP joint systems
    example: Al-alloy/CFRP joint systems offer lightweight structure, fatigue behaviour and impact resistance, and are widely used in aerospace; galvanic corrosion at the aluminium interface is the main challenge.
    source: sci-rep-2022-galvanic
    where: Introduction
supply:
  - subject: Carbon fibre (PAN-based), manufacturing sites for the Toray T700S grade
    abundance: 'Not applicable: synthetic fibre made from a polymer precursor; no crustal abundance applies'
    producers: []
    manufacture: Torayca T700S is manufactured in France, Japan, the USA and Korea, according to the Toray data sheet. No production shares by country were read in a fetched source.
    source: toray-t700s
    where: Introduction paragraph of the Torayca T700S data sheet
risks:
  hazards:
    - text: PubChem aggregates ECHA notifications for bisphenol A diglycidyl ether (BADGE), a common epoxy resin monomer. Skin irritation (H315), allergic skin reaction (H317) and serious eye irritation (H319) are each reported in more than 99.9 % of hazard-reporting notifications; H411 (toxic to aquatic life with long lasting effects) appears in 50.9 %. The HexPly 8552 formulation is not published, so this applies to the monomer, not to the cured laminate.
      ghs:
        - 'H315: Causes skin irritation'
        - 'H317: May cause an allergic skin reaction'
        - 'H319: Causes serious eye irritation'
        - 'H411: Toxic to aquatic life with long lasting effects'
      source: pubchem-badge
      where: GHS Classification, aggregated reports for CID 2286
    - text: The carbon fibre safety data sheet says inhalation of dust may cause irritation of the respiratory system and dust can cause eye irritation. Carcinogenicity, reproductive toxicity and sensitisation are listed as not classified. Dust from cutting, sanding or machining cured CFRP is the practical concern.
      ghs: []
      source: rave-cf-sds
      where: Section 8.2 (exposure controls) and Section 11 (symptoms, if inhaled and if in eyes)
  failure_risks:
    - source: nasa-otell-1978
      where: Introduction, two modes of property degradation
      mode: Moisture-driven loss of properties at elevated temperature
      consequence: 'Absorbed moisture gives two effects: reversible plasticization of the epoxy matrix, and permanent degradation from microcracking in the matrix. The report says the permanent part cannot be predicted straightforwardly for composites.'
    - source: palmieri-2013
      where: Results, aged lap-shear specimens after 360 days
      mode: Bonded joint strength loss in hot, wet ageing
      consequence: After 360 days at 71 C and 85 % relative humidity, apparent shear strength fell from 36.6 MPa to 27.0 MPa, about 27 %, with nearly all failures still cohesive in the composite.
    - source: hexcel-8552
      where: Mechanical Properties table, 90 degree rows
      mode: Loading across the fibres
      consequence: Unidirectional IM7/8552 gives 64 MPa at 90 degrees, against 2724 MPa along the fibres. The datasheet gives both values, so layup choice decides how much of the fibre strength a part can use.
  side_effects:
    - text: Epoxy composites release volatiles in vacuum. Database total mass loss for graphite/epoxy laminates ranges from 0.11 % to 0.6 % in the rows read here, with the total dominated by outgassing rather than erosion. These are other resin systems, not HexPly 8552.
      source: nasa-outgassing-db
      where: Carbon fibre and graphite epoxy laminate rows, column TML
  mitigations:
    - text: Standard surface preparation (grit blasting, manual abrasion, peel ply) can lack precision and reproducibility. The authors propose laser ablation of the composite surface resin as a precise, reproducible preparation before bonding.
      source: palmieri-2013
      where: Abstract
  handling:
    - text: Keep prepreg at -18 C in a sealed moisture-proof bag; shelf life is 12 months from manufacture.
      source: hexcel-8552
      where: Prepreg Storage Life section
    - text: Operators should wear clean, impervious gloves when handling the resin and fibre.
      source: hexcel-8552
      where: Handling and Safety Precautions
gaps:
  - 'Supply shares by country for PAN-based carbon fibre: no readable source found. Search results were market-research blogs with conflicting figures, so none were used.'
  - 'Laminate density and fibre volume fraction for the HexPly 8552 IM7 prepreg: not extracted; the datasheet density row is for neat resin.'
  - 'Outgassing of HexPly 8552 or T700S specifically: the NASA database has no row for these systems. The rows used are other epoxy and graphite/epoxy systems.'
  - 'NASA outgassing database CSV has no unit row: percent is assumed for TML values.'
  - 'Atomic oxygen erosion of CFRP: no readable source with a number. A search snippet gave 0.42 % mass loss for a quasi-isotropic laminate in LEO, but the paper was not read, so it is not used.'
  - 'UV ageing of CFRP epoxy: no readable source found.'
  - 'Thermal cycling and microcracking in orbit: the sources read describe permanent microcracking qualitatively; no thermal-cycling number was read.'
  - 'Water uptake of a HexPly 8552 or CFRP laminate at saturation: not read. The 0.75 % value is for bonded joints aged 360 days; the 1996 NASA moisture-absorption curves are shown only as figures in the text.'
  - 'Galvanic corrosion of CFRP with aluminium in a marine or seawater test: no source found; the 3.5 wt% NaCl test is a laboratory coupon.'
  - Outgassing and total mass loss are not in the property canon; total_mass_loss is a snake_case name used here.
  - 'Critical-mineral status of PAN precursor and acrylonitrile: not read.'
  - The Toray 2500 composite row (T700S) has no stated layup in the datasheet.
  - 'Laminate CTE for the HexPly 8552 system: not found. The 0.18 ppm/K value is for graphite-epoxy coupons with a different layup and resin not named in the table.'
sources:
  hexcel-8552:
    title: HexPly 8552 mid-toughened, high strength, damage-resistant, structural epoxy matrix, Product Data Sheet
    id: Hexcel Corporation, Copyright 2020 (file uploaded 2026)
    url: https://www.hexcel.com/wp-content/uploads/2026/01/HexPly_8552_us_DataSheet-1.pdf
    year: 2020
    kind: datasheet
    license: manufacturer datasheet, values quoted for reference
  toray-t700s:
    title: Torayca T700S Carbon Fiber Data Sheet
    id: Toray Carbon Fibers Europe, test methods TY-QA-002, TY-QA-003
    url: https://toray-cfe.com/wp-content/uploads/2025/02/Torayca-T700S-Technical-Data-Sheet.pdf
    year: 2025
    kind: datasheet
    license: manufacturer datasheet, values quoted for reference
  nasa-tm104637:
    title: 'NASA Technical Memorandum 104637: Hygrothermal Properties of Composites'
    id: NASA TM 104637, P. Arsenovic, Goddard Space Flight Center, June 1996
    url: https://ntrs.nasa.gov/citations/19960041513
    year: 1996
    kind: report
    license: NASA NTRS public document
  nasa-cr187229:
    title: 'NASA Contractor Report 187229: Environmental and Strain Rate Effects on Graphite/Epoxy Composites'
    id: NASA CR-187229, K. Peimandis, Northwestern University, October 1991
    url: https://ntrs.nasa.gov/citations/19920011242
    year: 1991
    kind: report
    license: NASA NTRS public document
  nasa-otell-1978:
    title: 'Synthesis of Improved Moisture Resistant Polymers: final report'
    id: NTRS 19790009882, M. K. Otell, TRW Defense and Space Systems Group, NASA contract NAS3-21011
    url: https://ntrs.nasa.gov/citations/19790009882
    year: 1978
    kind: report
    license: NASA NTRS public document
  palmieri-2013:
    title: Supersonic retropulsion surface preparation of carbon fiber reinforced epoxy composites for adhesive bonding
    id: F. L. Palmieri, M. A. Belcher, C. J. Wohl, K. Y. Blohowiak, J. W. Connell, NASA Langley and Boeing
    url: https://ntrs.nasa.gov/citations/20130013699
    year: 2013
    kind: paper
    license: NASA NTRS public document
  nasa-outgassing-db:
    title: NASA outgassing database (legacy Outgassing_Db CSV)
    id: NASA data.nasa.gov, legacy Outgassing_Db
    url: https://data.nasa.gov/docs/legacy/Outgassing_Db/Outgassing_Db_rows.csv
    kind: database
    license: NASA open data
  sci-rep-2022-galvanic:
    title: Galvanic corrosion protection of Al-alloy in contact with carbon fibre reinforced polymer through plasma electrolytic oxidation treatment
    id: Scientific Reports 12, 4532 (2022)
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8927304/
    year: 2022
    kind: paper
    license: CC-BY 4.0 (open access)
  pubchem-badge:
    title: 'PubChem: Bisphenol A diglycidyl ether (CID 2286), GHS classification summary'
    id: PubChem, National Center for Biotechnology Information
    url: https://pubchem.ncbi.nlm.nih.gov/compound/2286
    year: 2026
    kind: database
    license: PubChem public data
  rave-cf-sds:
    title: 'Safety data sheet: High purity carbon fibers in carbon fiber threads, document SDS00170CC1016 version 4.0'
    id: Rave Scientific, Regulation (EC) No 1907/2006 Art. 31, dated October 5th 2022
    url: https://ravescientific.com/images/pdf/SDS00170CC1016-01_Carbon_Fibre.pdf
    year: 2022
    kind: datasheet
    license: supplier safety data sheet, quoted for reference
  wiki-carbon-fibre:
    title: Carbon fiber (Wikipedia article, Carbon fibers)
    id: Wikipedia, article Carbon fibers
    url: https://en.wikipedia.org/wiki/Carbon_fibers
    year: 2026
    kind: web
    license: CC BY-SA 4.0
license: CC-BY-4.0
updated: '2026-10-19'
review:
  status: draft
  method: assistant
  checked_values: 17
  unreachable: 1
  caveats: 6
  note: 'Deepen pass on 2026-10-19: five new properties read from NASA TM 104637 (CTE), the NASA outgassing database (three TML rows) and Palmieri et al. 2013 (water uptake), each checked against fetched text. Unreachable: atomic oxygen and UV numbers for CFRP. Caveats: the 0.18 ppm/K CTE is for graphite-epoxy coupons, not HexPly 8552; TML rows are other resin systems; the 0.75 % water uptake is for bonded joints.'
story:
  recipe:
    line: Carbon fibre is made by spinning a precursor polymer, mostly polyacrylonitrile (PAN), into filaments, oxidising them in air and carbonising them to drive off non-carbon atoms. The fibre is impregnated with a toughened amine-cured epoxy; the HexPly 8552 prepreg is cured at 350 F.
    parts:
      - name: Carbon fibre (PAN-based)
        share: 62-67 % by mass (computed as 100 minus the printed 33-38 % resin content)
        role: Carries the load along its length and gives the stiffness and strength of the laminate.
      - name: Toughened amine-cured epoxy resin
        share: 33-38 % by mass (printed resin content of the HexPly 8552 prepreg)
        role: Holds the fibres in place, transfers load between them and sets the service temperature.
  compare_rows:
    - scope: material
      label: Strength along the fibres
      benchmark: ultimate_tensile_strength
    - scope: material
      label: Stiffness along the fibres
      benchmark: elastic_modulus
    - scope: material
      label: Density
      benchmark: density
  handling:
    - Keep prepreg frozen at -18 C in a sealed bag until lay-up; shelf life is 12 months from manufacture.
    - Wear clean, impervious gloves when handling resin and fibre.
    - Cutting, sanding or machining cured CFRP makes dust. Use ventilation, avoid dust formation, and dampen or vacuum spills.
    - 'Check the SDS for the product you handle: the epoxy monomer carries skin and sensitisation hazards (H317 in the PubChem record).'
  risk_groups:
    - title: For people
      lead: The sources read here describe the composite and its resin as a structural material, not as a hazard to people in use.
      level: 1
      verdict: No hazard data read
      points:
        - label: Handling prepreg
          line: Hexcel recommends that operators wear clean, impervious gloves to reduce skin contact with the prepreg. Shelf life is 12 months at -18 C in a sealed bag.
    - title: If it fails
      lead: The 90 degree strength is the weak direction. Failures found in the sources are about loading across the fibres.
      points:
        - label: Loading across the fibres
          line: Unidirectional IM7/8552 gives 64 MPa at 90 degrees, against 2724 MPa along the fibres. The datasheet gives both values, so layup choice decides how much of the fibre strength a part can use.
        - label: Heat
          line: The HexPly 8552 matrix is rated to a service temperature of 121 C (250 F). Above that limit the datasheet gives no data.
    - title: Handling and storage
      points:
        - label: Keep it cold until use
          line: Tack life is 10 days at room temperature and out life is 30 days. Keep the prepreg frozen until it is laid up.
  why: 'Carbon-fibre reinforced epoxy combines high stiffness and strength with low density. Unidirectional IM7/8552 laminate reaches 164 GPa along the fibres and 2724 MPa at 0 degrees, and the T700S fibre itself is rated at 4900 MPa and 230 GPa with a density of 1.8 g/cm3. The matrix sets the working limits: the neat resin density is 1.3 g/cm3 and the service limit is 121 C.'
  compare: The Toray composite row gives 2550 MPa for T700S in a Toray 2500 epoxy, against 4900 MPa for the fibre alone, so the matrix and test conditions take off about half the fibre strength in that test.
  can_do:
    - where: Structures
      line: A quasi-isotropic 25/50/25 IM7/8552 laminate gives 717 MPa tensile strength. Hexcel lists it among typical uses for space launchers and primary aircraft structures.
      label: Property
  good_for:
    - Stiff, light structures that must carry load along known directions.
  watch_out:
    - Check the 90 degree strength and the 121 C service limit before you set the layup and environment.
  verdict: Strong and stiff along the fibres; weak across them and limited by the epoxy at about 121 C.
  uses:
    - where: Launcher and spacecraft structures
      line: Hexcel lists space launchers and space and defense aircraft structures among typical uses of HexPly 8552.
documents:
  - title: HexPly 8552 Product Data Sheet (Hexcel)
    type: datasheet
    url: https://www.hexcel.com/wp-content/uploads/2026/01/HexPly_8552_us_DataSheet-1.pdf
    year: 2020
  - title: Torayca T700S Carbon Fiber Data Sheet (Toray)
    type: datasheet
    url: https://toray-cfe.com/wp-content/uploads/2025/02/Torayca-T700S-Technical-Data-Sheet.pdf
    year: 2025
  - title: 'NASA TM 104637: Hygrothermal Properties of Composites'
    type: report
    url: https://ntrs.nasa.gov/citations/19960041513
    year: 1996
  - title: 'NASA CR-187229: Environmental and Strain Rate Effects on Graphite/Epoxy Composites'
    type: report
    url: https://ntrs.nasa.gov/citations/19920011242
    year: 1991
  - title: 'NTRS 19790009882: Synthesis of Improved Moisture Resistant Polymers (final report)'
    type: report
    url: https://ntrs.nasa.gov/citations/19790009882
    year: 1978
  - title: 'Palmieri et al.: Supersonic retropulsion surface preparation of carbon fiber reinforced epoxy composites for adhesive bonding'
    type: paper
    url: https://ntrs.nasa.gov/citations/20130013699
    year: 2013
  - title: NASA outgassing database (legacy Outgassing_Db CSV)
    type: database
    url: https://data.nasa.gov/docs/legacy/Outgassing_Db/Outgassing_Db_rows.csv
    year: 2026
  - title: Galvanic corrosion protection of Al-alloy in contact with CFRP through plasma electrolytic oxidation (Scientific Reports)
    type: paper
    url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8927304/
    year: 2022
  - title: 'PubChem: Bisphenol A diglycidyl ether (CID 2286), GHS classification summary'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/2286
    year: 2026
  - title: Rave Scientific safety data sheet, carbon fibers SDS00170CC1016 v4.0
    type: sds
    url: https://ravescientific.com/images/pdf/SDS00170CC1016-01_Carbon_Fibre.pdf
    year: 2022