Boron Fiber Composite B-FIL
Grade
B-FIL = boron filament
The raw reinforcement itself, bought as a spool for prepregging, wire-wound rocket cases or MMC preforms.
Values for the B-FIL condition
Other Boron Fiber Composite grades and fills
Boron Fiber Composite is listed in 7 conditions; see the grade overview at Boron Fiber Composite.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
cross-plied boron/epoxy laminate | Choose when biaxial load or dimensional stability in two directions matters more than peak 0° stiffness. | 700 | 780 | 0.7 | 90 Shore D |
boron fiber reinforced aluminium (metal matrix) | Diffusion-bonded MMC for high-temperature, high-conductivity structure (e.g. Shuttle Orbiter truss tubes); heavier, expensive, and requires hot-press consolidation. | 900 | 1,400 | 0.8 | — |
boron fiber in polyimide / bismaleimide matrix | For sustained service above 200 °C where an epoxy matrix would soften; harder to process and lower interlaminar toughness. | — | 1,400 | 0.7 | 92 Shore D |
Boron/carbon hybrid epoxy tape | Use to cut cost and weight versus pure boron while keeping much of the compressive strength; note the carbon makes it electrically conductive again. | — | 1,450 | 0.85 | 89 Shore D |
B-EP-UDDefault unidirectional boron/epoxy prepreg laminate (121 °C cure) | Standard bonded-repair and stiffener material: highest compressive strength per weight, electrically insulating so it can be bonded straight onto aluminium. | — | 1,500 | 0.75 | 90 Shore D |
177 °C-cure high-temperature boron/epoxy | Pick when the part or repair must run hot (supersonic skins, engine-area doublers) and a 177 °C autoclave cure is available. | — | 1,550 | 0.75 | 91 Shore D |
B-FILThis page Boron filament | The raw reinforcement itself, bought as a spool for prepregging, wire-wound rocket cases or MMC preforms. | — | 3,600 | 0.9 | — |
What is Boron Fiber Composite B-FIL?
Boron Fiber Composite B-FIL is Boron Fiber Composite in the B-FIL grade — the raw reinforcement itself, bought as a spool for prepregging, wire-wound rocket cases or MMC preforms. Boron Fiber Composite B-FIL has a tensile strength of 3,600 MPa (522 ksi), stronger than 89% of composite grades. Elongation at break is 0.9% and the elastic modulus is 400 GPa (58 Msi). Boron Fiber Composite B-FIL has a density of 2.57 g/cm³ (0.0928 lb/in³), heavier than 83% of composite grades. Its glass-transition temperature is 160°C (320 °F). B-EP-UD is the default condition FabDigit quotes; B-FIL is available on request or by drawing note.
Advantages
- Stiff — 400 GPa (58 Msi), better than 97% of composite grades
- Tough — resists crack growth — 35 MPa·√m (31.9 ksi·√in), better than 91% of composite grades
- High service temperature — 500°C (932 °F), better than 87% of composite grades
- Low moisture uptake — 0.1%, better than 85% of composite grades
- Conducts heat well — 27 W/m·K (15.6 BTU/hr·ft·°F), better than 80% of composite grades
Limitations
- Difficult to machine — 3/100, worse than 99% of composite grades
- High embodied carbon — 95 kg CO₂/kg, worse than 99% of composite grades
- Hard to polish — 20/100, worse than 90% of composite grades
- Heavy — 2.57 g/cm³ (0.0928 lb/in³), worse than 83% of composite grades
- Limited ductility — 0.9%, worse than 80% of composite grades
Boron Fiber Composite B-FIL properties
Typical room-temperature values for Boron Fiber Composite B-FIL; 11 are specific to this condition. Other listed values are Boron Fiber Composite reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
Boron Fiber Composite B-FIL has a density of 2.57 g/cm³ (0.0928 lb/in³), heavier than 83% of composite grades. Its glass-transition temperature is 160°C (320 °F).
Mechanical14
Boron Fiber Composite B-FIL has a tensile strength of 3,600 MPa (522 ksi), stronger than 89% of composite grades. Elongation at break is 0.9% and the elastic modulus is 400 GPa (58 Msi).
Thermal7
Boron Fiber Composite B-FIL is rated for continuous service to 500°C (932 °F). It conducts heat at 27 W/m·K (15.6 BTU/hr·ft·°F), better than 80% of composite grades. Thermal expansion is 4.8 µm/m·K (2.67 µin/in·°F).
Electrical1
Boron Fiber Composite B-FIL has an electrical resistivity of 0.15 Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of composite grades. UV resistance is fair.
Sustainability3
Producing a kilogram of Boron Fiber Composite B-FIL takes about 1,500 MJ of energy and emits 95 kg of CO₂ — more than 100% of composite grades. Typical recycled content is 0%.
Manufacturability3
Boron Fiber Composite B-FIL's machinability is not recommended (3/100, worse than 99% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Boron Fiber Composite B-FIL
Is Boron Fiber Composite easy to machine?
Extremely abrasive 100–140 µm filaments destroy carbide — use abrasive waterjet, diamond-plated routers/saws and diamond core drills with dust extraction.
Can Boron Fiber Composite be welded?
Not weldable; joints are adhesively bonded (film adhesive) or mechanically fastened with oversized, well-supported holes.
Can Boron Fiber Composite be formed, bent or molded?
Hand-laid unidirectional prepreg tape only (fibres cannot be woven or tightly draped); vacuum-bag/autoclave cure at 121 or 177 °C, or heat-blanket cure for on-aircraft repair patches.
What surface finishes work on Boron Fiber Composite?
Seal edges and paint/prime for UV and moisture protection; the laminate is dielectric, so eddy-current inspection of the metal beneath a bonded patch remains possible.
Boron Fiber Composite chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| boron fiber (CVD B on W core)≈50 vol% in UD prepreg; W core ≈ 1–3 wt% of the fibre | 55 – 70 | 65 |
| epoxy matrix121 °C or 177 °C cure aerospace epoxy | ≥ 30 (balance) | — |
Boron Fiber Composite B-FIL — frequently asked
What is Boron Fiber Composite B-FIL used for?
Boron Fiber Composite B-FIL is typically used for aircraft structural repair patches, military aerospace skins and sporting goods (golf shafts). In short: very high compressive strength; dielectric repair patches; extremely abrasive filaments.
What is the tensile strength of Boron Fiber Composite B-FIL?
Boron Fiber Composite B-FIL has a typical tensile strength of 3,600 MPa (522 ksi) — stronger than 89% of composite grades. Strength varies by condition: see the 7 listed tempers.
Is Boron Fiber Composite B-FIL easy to machine?
Not especially — machinability is rated not recommended (3/100, worse than 99% of composite grades). Extremely abrasive 100–140 µm filaments destroy carbide — use abrasive waterjet, diamond-plated routers/saws and diamond core drills with dust extraction.
Can Boron Fiber Composite B-FIL be welded?
Not weldable; joints are adhesively bonded (film adhesive) or mechanically fastened with oversized, well-supported holes.
What surface finishes work on Boron Fiber Composite B-FIL?
Seal edges and paint/prime for UV and moisture protection; the laminate is dielectric, so eddy-current inspection of the metal beneath a bonded patch remains possible.
Can Boron Fiber Composite B-FIL be formed, bent or molded?
Hand-laid unidirectional prepreg tape only (fibres cannot be woven or tightly draped); vacuum-bag/autoclave cure at 121 or 177 °C, or heat-blanket cure for on-aircraft repair patches.
What is the maximum service temperature of Boron Fiber Composite B-FIL?
Boron Fiber Composite B-FIL is rated for continuous use to about 500°C (932 °F), and briefly to 190°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Boron Fiber Composite B-EP-UD and Boron Fiber Composite B-AL?
B-EP-UD is the default condition — standard bonded-repair and stiffener material: highest compressive strength per weight, electrically insulating so it can be bonded straight onto aluminium. B-AL: diffusion-bonded MMC for high-temperature, high-conductivity structure (e.g. Shuttle Orbiter truss tubes); heavier, expensive, and requires hot-press consolidation.
Sources
- ASM Handbook Vol. 21: Composites — ASM International (2001)
- CMH-17 (MIL-HDBK-17) Composite Materials Handbook, Vol. 1–3 — SAE International / CMH-17 (2012)
- Boron filament and boron/epoxy prepreg product data — Specialty Materials, Inc. (formerly Textron Specialty Materials) (2020)
- Composite Repair of Metallic Aircraft Structure (Baker & Jones) — AGARD/NATO (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.