Carbon Fiber Reinforced PEEK (CFR-PEEK): Continuous vs Short Fiber
Carbon-fibre-reinforced polyetheretherketone (CFR-PEEK) has become the metal-replacement material of choice in aerospace, medical, semiconductor, and hydrogen-energy components that need strength, stiffness, and low weight at high temperature. But "CFR-PEEK" is not one material. The architecture of the carbon fibre — continuous (unidirectional / woven) versus short (chopped) fibre — fundamentally changes the resulting engineering properties, from tensile strength and modulus to wear and cost. This guide compares the two architectures with real data, so you can specify the right CFR-PEEK for your part.
1. The One-Line Difference
- Short (chopped) fibre CFR-PEEK: moulded or machined from a pellet/compound where short carbon fibres reinforce the PEEK matrix. Inexpensive, isotropic, injection/compression mouldable — but tensile strength typically in the ~200 MPa class or below and modulus a few times that of unreinforced PEEK.
- Continuous fibre (unidirectional / woven) CFR-PEEK: laminates where long aligned or woven carbon fibres carry load. Anisotropic, much stronger and stiffer along the fibre direction — tensile strength commonly reaching the several-hundred-MPa class (and well beyond with aerospace-grade laminates) — but far more complex and costly to process.
2. Mechanical Comparison (With Real Values)
The table below combines published datasheet ranges with measured values for short-fibre CFR-PEEK. Continuous-fibre figures span a range because strength depends on fibre volume fraction, layup, and test direction.
| Property | Unreinforced PEEK | Short-fibre CFR-PEEK | Continuous-fibre CFR-PEEK |
|---|---|---|---|
| --- | --- | --- | --- |
| Tensile strength (23 °C) | ~95–100 MPa | ~200 MPa class (see below) | Several hundred MPa (e.g., up to ~700–900 MPa in aligned laminates) |
| Tensile modulus | ~4 GPa | ~15–25 GPa | Can exceed ~100 GPa along fibre |
| Density (g/cm³) | ~1.30 | ~1.4–1.6 | ~1.5–1.7 |
| CTE | Moderate | Low | Near-zero along fibre |
| Wear / stiffness | Baseline | ✔ Improved | ✔ Highest (anisotropic) |
| Processability | Injection/extrusion/CNC | Injection/compression mouldable, CNC machinable | Laminated, thermostamping; limited machining of laminates |
| Cost | Lower | Moderate | High |
Sources: Victrex® CFR-PEEK datasheets; aerospace CFR-PEEK laminate data; measured short-fibre CFR-PEEK values from Dalian Luyang (see below).
Measured short-fibre CFR-PEEK at Dalian Luyang (LY-501 / LY-205)
From our internal Material Properties Table, measured on ISO test methods:
| Grade | Density (g/cm³) | Tensile strength @23 °C | Flexural strength @23 °C | Coefficient of friction | Wear volume (×10⁻³ cm³) |
|---|---|---|---|---|---|
| --- | --- | --- | --- | --- | --- |
| LY-501-2 (CFR-PEEK) | 1.6 | 105 MPa | 186 MPa | — | — |
| LY-205-2 (CFR-PEEK, high-performance wear grade) | 1.39 | 202 MPa | 305 MPa | 0.13 | 0.86 |
The LY-205-2 value (tensile ~202 MPa, coefficient of friction 0.13, very low wear volume 0.86 × 10⁻³ cm³) shows what a well-engineered short-fibre CFR-PEEK can achieve in real moulded/machined parts — far stronger and lower-wear than unreinforced PEEK, at a cost and processability a short-fibre compound allows.
3. When to Use Short-Fibre CFR-PEEK
Short-fibre CFR-PEEK is the right choice when:
- You need higher stiffness and lower CTE than unreinforced PEEK, with better wear resistance and lower coefficient of friction.
- Your part is a complex 3D geometry best made by injection or compression moulding.
- Cost and processability matter — short-fibre compounds mould like standard PEEK and are CNC-machinable from stock.
- The load is roughly multi-directional, so isotropic behaviour is acceptable.
Typical parts: gears, bearing cages/seats, wear pads, structural brackets, pump impellers, valve internals, seals/back-up rings needing stiffness, and electrolyzer wear components.
4. When to Use Continuous-Fibre CFR-PEEK
Continuous-fibre CFR-PEEK is chosen when performance dominates cost:
- You need maximum specific strength and stiffness along defined load paths (the several-hundred-MPa tensile class).
- Dimensional stability and near-zero CTE along the fibre are critical.
- Part geometry is flat or gently curved (plates, panels, ribs, housings) — continuous fibre cannot faithfully follow sharp corners.
- You can afford laminate processing (unidirectional tape, woven fabric, thermostamping, consolidation) and the associated tooling.
Typical parts: aerospace structural panels, medical implant plates, high-end housings, lightweight frames for large equipment.
The decisive trade: isotropic, mouldable strength at the ~200 MPa class (short fibre) versus anisotropic, laminate-only strength into the several-hundred-MPa class (continuous fibre).
5. Processability & Cost Decision
| Factor | Short-fibre CFR-PEEK | Continuous-fibre CFR-PEEK |
|---|---|---|
| --- | --- | --- |
| Injection/compression moulding | ✔ Yes | ✗ Lamination/thermostamp |
| CNC machining from stock | ✔ Yes | Limited (layers delaminate) |
| Complex 3D shape capability | ✔ Good | ✗ Poor |
| Load direction flexibility | ✔ Isotropic | ✗ Must align to fibre |
| Relative cost | Moderate | High |
| Production scalability | High (moulding) | Lower, specialised |
For most machined and moulded industrial parts, short-fibre CFR-PEEK is the pragmatic, cost-effective choice; reserve continuous-fibre for structural laminates where its strength premium justifies the cost.
6. Specification Checklist for CFR-PEEK
- [ ] Fibre architecture specified: short (chopped) vs continuous (UD/woven)
- [ ] Fibre content by weight/volume and direction of reinforcement
- [ ] Datasheet with ISO/ASTM methods for tensile, flexural, thermal (Tg, HDT), and wear
- [ ] Surface/edge condition appropriate to application (no delamination risk for machined laminates)
- [ ] CTE and dimensional-stability data at operating temperature
- [ ] Wear/friction data for moving or sealing parts
- [ ] ISO 9001 / ISO 13485 and resin traceability
- [ ] Prototyping allowed in machined short-fibre CFR-PEEK before volume
Frequently Asked Questions
- How strong is continuous-fibre CFR-PEEK? Aligned continuous-fibre laminates reach tensile strengths of several hundred MPa (into the ~700–900 MPa class at high fibre fraction), versus the ~200 MPa class typical of short-fibre CFR-PEEK.
- Can you machine continuous-fibre CFR-PEEK? Only limitedly — machining breaks the continuous reinforcement and can cause delamination. It is best used as a laminate in flat or gently curved forms.
- Which CFR-PEEK should I pick for a moulded gear or wear part? Short-fibre CFR-PEEK — it is mouldable to complex geometry, offers excellent wear and stiffness (e.g., LY-205-2: friction 0.13, low wear volume), and is far more economical than laminate processing.
Related Topics
- PEEK Properties: A Complete Engineering Guide
- CNC Machining vs Compression Molding vs Injection Molding for PEEK
- PEEK vs Metals: When Does a Polymer Part Beat Steel or Titanium?
Dalian Luyang Technology Development Co., Ltd. (www.newmaterialchina.com) manufactures PEEK, PI, and PTFE precision parts — seals, inserts, machined components, and electrolyser frames — under ISO 9001 and ISO 13485. Established 2006. Contact: liyulong@luyangkeji.com · WhatsApp +86 15989781752. This guide is educational reference material; always verify against your chosen grade's official datasheet.