FRP round tube is also written CHS (circular hollow section). It is made by pultrusion (straight, constant section) or by filament winding (pipes, vessels). Here we treat pultruded structural tube.
Section properties (calculated)
Calculated from geometry for a plain circular tube at a density of 1.9 g/cm³. Real tubes vary with glass content and tolerance, so use the supplier’s catalogue values for final design. I = second moment of area, S = section modulus.
| OD (mm) | Wall (mm) | ID (mm) | kg/m | I (cm⁴) | S (cm³) |
|---|---|---|---|---|---|
| 20 | 3 | 14 | 0.30 | 0.6 | 0.6 |
| 25 | 3 | 19 | 0.39 | 1.3 | 1.0 |
| 32 | 4 | 24 | 0.67 | 3.5 | 2.2 |
| 38 | 4 | 30 | 0.81 | 6.3 | 3.3 |
| 50 | 5 | 40 | 1.34 | 18.1 | 7.2 |
| 60 | 5 | 50 | 1.64 | 32.9 | 11.0 |
| 76 | 6 | 64 | 2.51 | 81.4 | 21.4 |
| 89 | 6 | 77 | 2.97 | 135.4 | 30.4 |
| 100 | 6 | 88 | 3.37 | 196.5 | 39.3 |
| 114 | 8 | 98 | 5.06 | 376.3 | 66.0 |
Worked deflection check
A 50×5 mm tube (I = 18.1 cm⁴), simply supported over 1.5 m with 400 N at mid-span and E = 17 GPa:
δ = P·L³ / (48·E·I) = 400 × 1500³ / (48 × 17000 × 181132) = 9.1 mm (typical limit L/200 = 7.5 mm).
Bending-only estimate; allow extra margin for shear deformation, creep under permanent loads and impact, and have the design checked by an engineer used to FRP.
Tube, pipe or profile?
| Term | Meaning | Use |
|---|---|---|
| Tube / CHS | Structural round hollow section, rated by size and wall | Posts, rails, handles, frames |
| Pipe | Made to carry fluid, rated by pressure (PN) and diameter | Process and water lines (filament wound or similar) |
| Rod | Solid round section | See solid vs hollow rods |
Resin choice follows the environment (resin guide). Square tube equivalents are in FRP square tube.
Frequently asked questions
Can I use FRP tube for pressure?
Pultruded structural tube is not rated for pressure. For fluid service ask for filament-wound pipe designed to the pressure rating you need.
Can round tubes be telescoped?
Yes, with close tolerances on OD and ID; specify the clearance you need so tubes slide without play.
Send us your requirement
Guangdong Haikuo Composite Materials Co., Ltd. (Huizhou, Guangdong) designs pultrusion moulds in-house and produces custom FRP profiles. Send a drawing, a sample or just the application and the environment, and we will tell you what is feasible.
Email: [email protected] | WhatsApp: +86 189 5198 8522