Flax fibre (natural bast fibre)
Cellulose-based bast fibre from the flax stem (Linum usitatissimum L.)
Flax fibre is the bast fibre from the stem of the flax plant (Linum usitatissimum L.), used to reinforce composites as a plant-based alternative to glass fibre.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Tensile strength
1500 to 1800 MPa
Compressive strength
1200 MPa
Stiffness
52.4 GPa
Stretch before break
2.15 %
Recipe, share of the weight
- Up to 90% of the G-layer; the whole-fibre share was not found in the sources readCellulose
- Absent from the G-layer; other layers not coveredLignin and xylan
Best for
Plant-based reinforcement for composites, where the review says flax can substitute for glass fibres
Weakest at
Strength depends on the isolation and decortication process; no density, ageing or supply data found yet
Risk at a glance
- People No data. No hazard data recorded
- If it fails High. Kink bands from the standard decortication process
- Corrosion No data. No corrosion data recorded
Quick facts: Flax fibre (natural bast fibre)
| Property | Value | Basis |
|---|---|---|
| Tensile strength | 976 to 1,800 MPa | 2 sourced values across conditions |
| Young's modulus | 52.4 GPa | 1 sourced value |
What is the tensile strength of Flax fibre?
Flax fibre has a tensile strength of 976 to 1,800 MPa. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the Young's modulus of Flax fibre?
Flax fibre has a Young's modulus of 52.4 GPa. The source and test conditions are listed in the properties table on this page.
What is Flax fibre used for?
Uses recorded in the sources include Flax fibre composite reinforcement (technical fibres or short fibres in a polymer matrix).
Why it exists
Flax fibre is the bast fibre from the stem of the flax plant, used in composites as a plant-based alternative to glass fibre. Its cell walls are thick, and the review describes the G-layer, the fibre-specific cell-wall layer, as rich in cellulose. The review describes flax as a renewable reinforcement with mechanical properties in a similar range to glass fibres, but this profile records the figures the two sources actually give.
Where it's used
Composite reinforcement
The review states that flax fibres reinforce composite materials, as technical fibre bundles or as short fibres impregnated with a polymer matrix. No space application was found in the sources read.
Recipe
Cellulose-based bast fibre from the flax stem (Linum usitatissimum L.); a natural fibre bundle, not one chemical compound, so no single formula
Flax fibre is a bundle of elongated plant cells. The thick cell walls are mostly cellulose in the G-layer, the fibre-specific layer, where the cellulose microfibrils run almost along the fibre axis.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Cellulose | Up to 90% of the G-layer; the whole-fibre share was not found in the sources read | Main load-bearing polymer. In the G-layer it is highly crystalline and its microfibrils lie at a small angle to the fibre axis. |
| Lignin and xylan | Absent from the G-layer; other layers not covered | Absent from the G-layer, according to the review. Their share in the rest of the cell wall was not found. |
Weight shares are as printed in the sources.
What it can do
Tensile strength
1500 to 1800 MPa
measured
Elementary flax fibres reached 1500 to 1800 MPa in tension, depending on the isolation procedure (Bos et al. 2002).
Compressive strength
1200 MPa
measured
Elementary flax fibres reached around 1200 MPa in a loop test, but the same paper says standard decortication can lower compressive strength severely.
Stiffness
52.4 GPa
measured
The review quotes an average elastic modulus of 52.4 GPa for flax fibre. The review quotes this figure from earlier work and does not measure it.
Stretch before break
2.15 %
measured
The review quotes a strain at break of 2.15% for flax fibre, again from earlier work.
How it compares
The review says flax fibres have a similar range of specific mechanical properties to glass fibres, which is why it presents them as a substitute. The sources read for this profile do not give a glass-fibre figure to set beside the flax values, so no side-by-side number is shown. The compare rows below list the three flax benchmarks that have a value in the record.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details.
| Measurement | Flax fibre (natural bast fibre) |
|---|---|
| Physical and electrical | |
| Cell-wall thickness of flax fibre, lower bound | > 10 μm7 |
| Other measurements | |
| Tensile strength of elementary flax fibres, range by isolation procedure | 1500 to 1800 MPa1 |
| Compressive strength of elementary flax fibres, loop test | 1200 MPa2 |
| Strength at break of flax fibre, as quoted in a review | 976 MPa3 |
| Average elastic modulus of flax fibre, as quoted in a review | 52.4 GPa4 |
| Strain at break of flax fibre, as quoted in a review | 2.15 %5 |
| Average diameter of flax fibre | 20 μm6 |
| Cellulose content of the G-layer in flax fibre cell walls | < 90 %8 |
| Cellulose microfibril angle in the G-layer | 8 to 10 °9 |
Why choose it, and why not
Good for
- Plant-based reinforcement for composites. The review says flax can substitute for glass fibres in this role.
- High tensile strength for a plant fibre. Elementary fibres reached 1500 to 1800 MPa (Bos et al. 2002).
Watch out for
- Strength depends on how the fibre is isolated. The review quotes 976 MPa, and Bos et al. 2002 measured 1500 to 1800 MPa, and the two are not the same test.
- Standard decortication can lower compressive strength severely (Bos et al. 2002), so compression values apply to hand-isolated fibres.
Strong and stiff for a plant fibre on the two sources read, but the record is thin: no density, supply or ageing data yet.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Tensile strength of elementary flax fibres, range by isolation procedure | Tensile tests by the authors (Bos et al. 2002), range as printed in the abstract | form elementary (single) flax fibres, decorticated and hand-isolatedtest tensionrange basis depending on the isolation procedure | — |
| 2 | Compressive strength of elementary flax fibres, loop test | Loop-test compression measurement by the authors (Bos et al. 2002); value as printed in the abstract | form elementary flax fibrestest loop testqualifier printed as around 1200 MPa | The same abstract says standard decortication can lower the compressive strength severely, so this figure is for hand-isolated fibres. |
| 3 | Strength at break of flax fibre, as quoted in a review | Quoted in an open-access review from earlier work; not measured by the review's authors | form flax fibre (form and test not stated in the review)basis figure quoted from earlier work the review cites | Lower than the 1500 to 1800 MPa range measured by Bos et al. (2002). The review does not say which isolation or test gave 976 MPa, so the two are not directly comparable. |
| 4 | Average elastic modulus of flax fibre, as quoted in a review | Quoted in an open-access review from earlier work; not measured by the review's authors | form flax fibre (form not stated in the review)basis figure quoted from earlier work the review cites | — |
| 5 | Strain at break of flax fibre, as quoted in a review | Quoted in an open-access review from earlier work; not measured by the review's authors | form flax fibre (form not stated in the review)basis figure quoted from earlier work the review cites | — |
| 6 | Average diameter of flax fibre | Quoted in an open-access review from earlier work (van Dam and Gorshkova); not measured by the review's authors | form flax fibrebasis average diameter for a fibre length of 25 mm, as quoted in the review | — |
| 7 | Cell-wall thickness of flax fibre, lower bound | Stated in an open-access review; the review does not name a measurement method for this figure | form flax fibre cell wallqualifier printed as more than 10 μm | — |
| 8 | Cellulose content of the G-layer in flax fibre cell walls | Stated in an open-access review; the review does not name a measurement method for this figure | layer G-layer, the fibre-specific cell-wall layer (not the whole fibre)qualifier printed as up to 90% | — |
| 9 | Cellulose microfibril angle in the G-layer | Stated in an open-access review; the review does not name a measurement method for this figure | layer G-layer, the fibre-specific cell-wall layernote microfibrils almost parallel to the fibre axis | — |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The review describes plant fibre manufacturing as a low hazard process for human health, but no safety data sheet was read for flax fibre.
- Decortication
- Bos et al. 2002 report that the standard decortication process induces kink bands in the fibres, and that these lower compressive strength severely.
- Not covered
- No safety data sheet, PubChem record or dust exposure data for flax fibre was read in this run.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Kink bands from the standard decortication processhigh severity | Standard decortication process, as described by Bos et al. 2002Kink bands form in the fibres and contain cracks bridged by microfibrils; the abstract says decortication can lower compressive strength severely. |
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
spore: profile
id: flax-fibre
spore_version: 0.2
family: flax
name: Flax fibre (natural bast fibre)
role: Plant-based reinforcement fibre for composites
category: composites
type: glass-fiber-reinforced
summary: Flax fibre is the bast fibre from the stem of the flax plant (Linum usitatissimum L.), used to reinforce composites as a plant-based alternative to glass fibre. Elementary flax fibres reached 1500 to 1800 MPa in tension and around 1200 MPa in a loop compression test (Bos et al. 2002), although a review quotes a lower tensile figure of 976 MPa. Density, ageing and supply data were not found in the two sources read for this profile.
best_for: Plant-based reinforcement for composites, where the review says flax can substitute for glass fibres
weakest_at: Strength depends on the isolation and decortication process; no density, ageing or supply data found yet
identity:
formula: Cellulose-based bast fibre from the flax stem (Linum usitatissimum L.); a natural fibre bundle, not one chemical compound, so no single formula
source: goudenhooft2019
where: Introduction and cell-wall layers section (cellulose-rich G-layer)
properties:
- benchmark: ultimate_tensile_strength
label: Tensile strength of elementary flax fibres, range by isolation procedure
value: 1500
value_high: 1800
bound: range
unit: MPa
scope: material
conditions:
form: elementary (single) flax fibres, decorticated and hand-isolated
test: tension
range_basis: depending on the isolation procedure
method: Tensile tests by the authors (Bos et al. 2002), range as printed in the abstract
status: ground
source: bos2002
where: Abstract, tensile strength sentence
- benchmark: compressive_strength
label: Compressive strength of elementary flax fibres, loop test
value: 1200
unit: MPa
scope: material
conditions:
form: elementary flax fibres
test: loop test
qualifier: printed as around 1200 MPa
method: Loop-test compression measurement by the authors (Bos et al. 2002); value as printed in the abstract
status: ground
note: The same abstract says standard decortication can lower the compressive strength severely, so this figure is for hand-isolated fibres.
source: bos2002
where: Abstract, compressive strength sentence
- benchmark: ultimate_tensile_strength
label: Strength at break of flax fibre, as quoted in a review
value: 976
unit: MPa
scope: material
conditions:
form: flax fibre (form and test not stated in the review)
basis: figure quoted from earlier work the review cites
method: Quoted in an open-access review from earlier work; not measured by the review's authors
status: ground
note: Lower than the 1500 to 1800 MPa range measured by Bos et al. (2002). The review does not say which isolation or test gave 976 MPa, so the two are not directly comparable.
source: goudenhooft2019
where: Introduction, paragraph comparing flax fibres with glass fibres
- benchmark: elastic_modulus
label: Average elastic modulus of flax fibre, as quoted in a review
value: 52.4
unit: GPa
scope: material
conditions:
form: flax fibre (form not stated in the review)
basis: figure quoted from earlier work the review cites
method: Quoted in an open-access review from earlier work; not measured by the review's authors
status: ground
source: goudenhooft2019
where: Introduction, paragraph comparing flax fibres with glass fibres
- benchmark: elongation
label: Strain at break of flax fibre, as quoted in a review
value: 2.15
unit: '%'
scope: material
conditions:
form: flax fibre (form not stated in the review)
basis: figure quoted from earlier work the review cites
method: Quoted in an open-access review from earlier work; not measured by the review's authors
status: ground
source: goudenhooft2019
where: Introduction, paragraph comparing flax fibres with glass fibres
- benchmark: fibre_diameter
label: Average diameter of flax fibre
value: 20
unit: μm
scope: material
conditions:
form: flax fibre
basis: average diameter for a fibre length of 25 mm, as quoted in the review
method: Quoted in an open-access review from earlier work (van Dam and Gorshkova); not measured by the review's authors
status: ground
source: goudenhooft2019
where: Introduction, paragraph on flax fibre applications
- benchmark: fibre_cell_wall_thickness
label: Cell-wall thickness of flax fibre, lower bound
value: 10
bound: lower
unit: μm
scope: material
conditions:
form: flax fibre cell wall
qualifier: printed as more than 10 μm
method: Stated in an open-access review; the review does not name a measurement method for this figure
status: ground
source: goudenhooft2019
where: Cell wall thickening section
- benchmark: cellulose_content
label: Cellulose content of the G-layer in flax fibre cell walls
value: 90
bound: upper
unit: '%'
scope: material
conditions:
layer: G-layer, the fibre-specific cell-wall layer (not the whole fibre)
qualifier: printed as up to 90%
method: Stated in an open-access review; the review does not name a measurement method for this figure
status: ground
source: goudenhooft2019
where: Cell wall layers section (G-layer description)
- benchmark: microfibril_angle
label: Cellulose microfibril angle in the G-layer
value: 8
value_high: 10
bound: range
unit: °
scope: material
conditions:
layer: G-layer, the fibre-specific cell-wall layer
note: microfibrils almost parallel to the fibre axis
method: Stated in an open-access review; the review does not name a measurement method for this figure
status: ground
source: goudenhooft2019
where: Cell wall layers section (G-layer description)
corrosion: []
risks:
hazards:
- text: The review says plant fibres have a 'low hazard manufacturing process for human health' compared with glass fibres, citing earlier work. No safety data sheet or PubChem hazard record for flax fibre was read in this run, so this is the only hazard statement held.
ghs: []
source: goudenhooft2019
where: Introduction, paragraph comparing plant fibres with glass fibres
failure_risks:
- mode: Kink bands from the standard decortication process
trigger: Standard decortication process, as described by Bos et al. 2002
consequence: Kink bands form in the fibres and contain cracks bridged by microfibrils; the abstract says decortication can lower compressive strength severely.
severity: high
source: bos2002
where: Abstract, compressive strength and kink band sentences
side_effects: []
handling: []
mitigations: []
uses:
- application: structures
device: Flax fibre composite reinforcement (technical fibres or short fibres in a polymer matrix)
example: The review states that flax fibres are used as reinforcement in composite materials, either as technical fibre bundles or as short fibres impregnated with a polymer matrix.
source: goudenhooft2019
where: Introduction, paragraph on composite reinforcement
supply: []
media: []
documents:
- title: 'Flax (Linum usitatissimum L.) Fibers for Composite Reinforcement: Exploring the Link Between Plant Growth, Cell Walls Development, and Fiber Properties (open access review)'
type: paper
url: https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00411/full
year: 2019
- title: Tensile and compressive properties of flax fibres for natural fibre reinforced composites (Journal of Materials Science, 2002)
type: paper
url: https://research.wur.nl/en/publications/tensile-and-compressive-properties-of-flax-fibres-for-natural-fib/
year: 2002
gaps:
- 'Density not recorded: the review quotes a fibre density of 1.53 with no unit printed, so the value was left out rather than assumed to be g/cm3.'
- Only two sources were read in this run. The site bar asks for 8 sources and 12 properties; this profile has 2 sources and 9 properties.
- Supply (producing countries with shares, abundance, critical-mineral lists) not found in any source read. The review covers plant growth and fibre structure, not production statistics.
- No corrosion, ageing, moisture absorption, UV or hygrothermal degradation data for flax fibre found in the two sources read.
- No vacuum, radiation, thermal-cycling, outgassing or flight data for flax fibre found. No space application source was found; the only use listed is terrestrial composite reinforcement.
- No safety data sheet, PubChem GHS record or occupational dust-exposure data for flax fibre were read. The hazard entry only quotes the review.
- Glass-fibre comparison values were not read. The review says flax and glass fibres have a similar range of specific properties, without a glass figure in the text read.
- 'Conflict held side by side: 976 MPa strength at break (quoted in the review) against 1500 to 1800 MPa tensile strength (Bos et al. 2002). The isolation and test behind 976 MPa is not stated.'
- 'Handling and storage of flax fibre: not found in the sources read.'
- 'Property names not in the canonical list: compressive_strength, fibre_diameter, fibre_cell_wall_thickness, cellulose_content, microfibril_angle.'
- Taxonomy has no natural-fibre composite type. Type set to glass-fiber-reinforced as the closest fibre-reinforced composite type.
- 'Source papers behind the review''s quoted figures (Lefeuvre and van Dam and Gorshkova) were not opened: the publisher links returned redirect pages with no text.'
sources:
goudenhooft2019:
title: 'Flax (Linum usitatissimum L.) Fibers for Composite Reinforcement: Exploring the Link Between Plant Growth, Cell Walls Development, and Fiber Properties'
id: doi:10.3389/fpls.2019.00411 (Front. Plant Sci. 10, 411); authors C. Goudenhooft, A. Bourmaud, C. Baley
url: https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00411/full
year: 2019
kind: paper
license: open access, Frontiers in Plant Science
bos2002:
title: Tensile and compressive properties of flax fibres for natural fibre reinforced composites
id: doi:10.1023/A:1014925621252 (J. Mater. Sci. 37(8), 1683-1692); authors H.L. Bos, M.J.A. van den Oever, O.C.J.J. Peters
url: https://research.wur.nl/en/publications/tensile-and-compressive-properties-of-flax-fibres-for-natural-fib/
year: 2002
kind: paper
license: CC-BY-4.0
updated: '2026-11-01'
review:
status: draft
method: assistant
checked_values: 9
unreachable: 0
caveats: 1
note: 'Read by an AI assistant on 2026-11-01 from the Frontiers review and the WUR abstract page only. Below the site bar: 2 sources, 9 properties, no supply, no ageing data. The 976 MPa row is a second-hand quote and conflicts with the 1500 to 1800 MPa range from Bos et al. 2002.'
story:
recipe:
line: Flax fibre is a bundle of elongated plant cells. The thick cell walls are mostly cellulose in the G-layer, the fibre-specific layer, where the cellulose microfibrils run almost along the fibre axis.
parts:
- name: Cellulose
role: Main load-bearing polymer. In the G-layer it is highly crystalline and its microfibrils lie at a small angle to the fibre axis.
share_note: Up to 90% of the G-layer; the whole-fibre share was not found in the sources read
source: goudenhooft2019
where: Cell wall layers section (G-layer description)
- name: Lignin and xylan
role: Absent from the G-layer, according to the review. Their share in the rest of the cell wall was not found.
share_note: Absent from the G-layer; other layers not covered
source: goudenhooft2019
where: Cell wall layers section (G-layer description)
risk_groups:
- title: For people
lead: The review describes plant fibre manufacturing as a low hazard process for human health, but no safety data sheet was read for flax fibre.
points:
- label: Decortication
line: Bos et al. 2002 report that the standard decortication process induces kink bands in the fibres, and that these lower compressive strength severely.
gap: No safety data sheet, PubChem record or dust exposure data for flax fibre was read in this run.
verdict: No safety data read
why: Flax fibre is the bast fibre from the stem of the flax plant, used in composites as a plant-based alternative to glass fibre. Its cell walls are thick, and the review describes the G-layer, the fibre-specific cell-wall layer, as rich in cellulose. The review describes flax as a renewable reinforcement with mechanical properties in a similar range to glass fibres, but this profile records the figures the two sources actually give.
uses:
- where: Composite reinforcement
line: The review states that flax fibres reinforce composite materials, as technical fibre bundles or as short fibres impregnated with a polymer matrix. No space application was found in the sources read.
can_do:
- label: Tensile strength
benchmark: ultimate_tensile_strength
line: Elementary flax fibres reached 1500 to 1800 MPa in tension, depending on the isolation procedure (Bos et al. 2002).
- label: Compressive strength
benchmark: compressive_strength
line: Elementary flax fibres reached around 1200 MPa in a loop test, but the same paper says standard decortication can lower compressive strength severely.
- label: Stiffness
benchmark: elastic_modulus
line: The review quotes an average elastic modulus of 52.4 GPa for flax fibre. The review quotes this figure from earlier work and does not measure it.
- label: Stretch before break
benchmark: elongation
line: The review quotes a strain at break of 2.15% for flax fibre, again from earlier work.
compare: The review says flax fibres have a similar range of specific mechanical properties to glass fibres, which is why it presents them as a substitute. The sources read for this profile do not give a glass-fibre figure to set beside the flax values, so no side-by-side number is shown. The compare rows below list the three flax benchmarks that have a value in the record.
compare_rows:
- label: Tensile strength of elementary fibres
benchmark: ultimate_tensile_strength
- label: Elastic modulus
benchmark: elastic_modulus
- label: Strain at break
benchmark: elongation
good_for:
- Plant-based reinforcement for composites. The review says flax can substitute for glass fibres in this role.
- High tensile strength for a plant fibre. Elementary fibres reached 1500 to 1800 MPa (Bos et al. 2002).
watch_out:
- Strength depends on how the fibre is isolated. The review quotes 976 MPa, and Bos et al. 2002 measured 1500 to 1800 MPa, and the two are not the same test.
- Standard decortication can lower compressive strength severely (Bos et al. 2002), so compression values apply to hand-isolated fibres.
verdict: 'Strong and stiff for a plant fibre on the two sources read, but the record is thin: no density, supply or ageing data yet.'
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Flax (Linum usitatissimum L.) Fibers for Composite Reinforcement: Exploring the Link Between Plant Growth, Cell Walls Development, and Fiber Properties | paper | 2019 | 10 values | |
| Tensile and compressive properties of flax fibres for natural fibre reinforced composites | paper | 2002 | 3 values |