Product Overview
Square carbon fiber tubes are pultruded CFRP profiles with a square or rectangular cross-section — combining the stiffness-to-weight advantage of carbon fiber with flat sides that simplify assembly, bonding, and mounting. Compared with round tube, a square carbon fiber tube resists rotation in clamps and brackets, sits flat against panels and rails, and gives predictable bolt-up surfaces for frames and structures.
IncomePultrusion produces square and rectangular carbon fiber tubes by pultrusion: continuous carbon fiber reinforcement in an epoxy matrix, pulled through a heated die for a consistent void-free profile along the full length. Cross-sections, wall thicknesses, and lengths are produced to drawing — from small precision profiles for UAV and robotics frames to larger structural sections for automation equipment.
For round profiles see pultruded carbon fiber tubes; for solid square sections see carbon fiber square rods.
Why Square: Square vs Round Carbon Tube
- Anti-rotation: flat sides lock into clamps and brackets — no pinning or adhesives needed to stop twist
- Easy assembly: flat mounting faces for panels, joints, and connectors; drilling and bolting are simpler than on round tube
- Space-efficient frames: square sections pack neatly into rectangular frames, trusses, and enclosures
- Predictable bonding: flat surfaces give consistent bond-line thickness for glued joints
Where the load case is pure bending with no mounting interfaces, round tube remains slightly more efficient per unit weight; where the structure must bolt, bond, or stack — square wins on assembly cost and reliability.
Technical Specifications
Mechanical Properties (Standard Epoxy Matrix)
| Property | Typical Value | Test Method |
|---|---|---|
| Tensile Strength | 1,650 MPa (240 ksi) | ASTM D3039 |
| Tensile Modulus | 134 GPa (19.5 msi) | ASTM D3039 |
| Compressive Strength | 1,200 MPa (174 ksi) | ASTM D695 |
| Flexural Strength | 1,370 MPa (200 ksi) | ASTM D790 |
| Flexural Modulus | 130 GPa (18.9 msi) | ASTM D790 |
| Density | ~1.55 g/cm³ | – |
Values are typical for standard unidirectional pultruded carbon/epoxy and align with our round tube data. Actual properties depend on fiber volume, layup, and wall construction — confirm against the batch test data for critical designs.
Sizes & Wall Thickness
| Cross-Section | Typical Range | Wall Thickness | Tolerance |
|---|---|---|---|
| Small square (5×5 to 12×12 mm) | UAV, robotics, instruments | 0.5–1.5 mm | ±0.1 mm |
| Medium square (12×12 to 30×30 mm) | Automation frames, gantries | 1.0–2.5 mm | ±0.15 mm |
| Large / rectangular (per drawing) | Structural sections | 1.5–3.0 mm | Per drawing |
- Custom cross-sections: non-standard square and rectangular dimensions produced to drawing
- Lengths: cut to specification; standard cutting or precision machining
- Options: high-temp epoxy or vinyl ester resin systems, sanded/coated surfaces, chamfered or machined ends, threaded inserts
Typical Applications
- UAV and drone frames: arms and chassis rails that bolt flat to center plates
- Robotics and automation: gantry beams, end-effector structures, linear-motion frames
- Instrumentation and optical structures: dimensionally stable frames that stay square
- Sporting and industrial equipment: handles, supports, and protective frames
- Prototyping and jigs: fast-assembly structural members for fixtures and test rigs
Pultruded vs Roll-Wrapped Square Tube
Our square carbon fiber tubes are pultruded: continuous fibers aligned along the profile axis, giving the best axial stiffness and consistency at production volumes, with economical pricing in repeat sizes. Roll-wrapped tube (a different process, better for very large diameters or complex fiber orientations) is covered in our roll-wrapping guide. For most frame and automation sections in the 5–50 mm range, pultrusion is the cost-effective route.
Frequently Asked Questions
What sizes of square carbon fiber tube can you make?
Common tooling covers small to medium squares (roughly 5×5 to 30×30 mm) with walls from 0.5 to 3.0 mm; larger and rectangular sections are produced to drawing. Send the cross-section and wall requirement for confirmation.
Is a square carbon fiber tube as strong as a round one?
Axial (tension/compression) properties are comparable for the same fiber content. Round tube is slightly more efficient in pure bending per unit weight; square tube wins wherever flat mounting faces, anti-rotation, or frame packing matter — which is most real assemblies.
Can square tubes be drilled and bolted?
Yes — flat sides make drilling and bolting straightforward. Use sharp carbide tooling, support the inner wall when drilling through, and consider local reinforcement or inserts for highly loaded bolt joints.
Do you offer custom lengths and end finishing?
Yes. Tubes are cut to specification, with chamfered, machined, or insert-fitted ends available. Sanded or coated surface finishes can be specified at quote stage.
What is the difference between your square tube and square carbon rod?
The tube is hollow — much lighter for the same outer dimension and suited to structural frames. The square rod is solid and suited to machining stock and small rigid parts.
What do you need for a quote?
Cross-section (outer dimension × wall thickness), length, quantity, tolerance, resin system if specified, and the application environment. Submit through the quote request page for a 24-hour response.
Ordering Information
Square carbon fiber tubes are produced to order. Standard and custom cross-sections are quoted from drawings or samples, with prototypes available before production quantities. Send your requirements through the quote request page — a quotation with material data support is returned within 24 hours. For the full profile range, see the carbon fiber rod & tube hub.
