How thick should a carbon fiber sheet be? Thickness, stiffness and weight explained

Pick the thickness from the stiffness you need, because bending stiffness grows with the cube of thickness while weight grows only in proportion. A 2 mm carbon sheet is 8 times as stiff in bending as a 1 mm sheet and twice as heavy. To replace an aluminum plate with the same bending stiffness, a woven carbon sheet needs about 8% more thickness and weighs about 36% less^[1]^[2].

t³bending stiffness grows with thickness cubed

8×stiffness from 1 mm to 2 mm

−36%weight vs aluminum at equal stiffness (woven carbon)

1–5 mmstandard sheet thicknesses

Thickness, stiffness and weight

Standard 3K T300 sheets come in 1 to 5 mm^[3]. Relative to a 1 mm sheet of the same size:

Thickness	Relative weight	Relative bending stiffness	Weight per m² (at 1.6 g/cm³)
1 mm	1	1	1.6 kg
2 mm	2	8	3.2 kg
3 mm	3	27	4.8 kg
4 mm	4	64	6.4 kg
5 mm	5	125	8.0 kg

Relative bending stiffness (1 mm = 1)

1 mm1

2 mm8

3 mm27

4 mm64

5 mm125

Replacing an aluminum plate

For the same bending stiffness, thickness scales with the cube root of the modulus ratio. With aluminum at 68.9 GPa and 2.7 g/cm³^[1] and a woven T300 laminate at 55 GPa^[2] and about 1.6 g/cm³^[1]:

Aluminum plate	Woven carbon sheet, same stiffness	Weight saving
2.0 mm	2.16 mm (order 2.5 mm, custom, or 3 mm, standard)	about 36%
3.0 mm	3.23 mm (order 3.5 mm, custom, or 4 mm, standard)	about 36%
5.0 mm	5.39 mm (custom thickness)	about 36%

Thickness ratio = (68.9 ÷ 55)^(1/3) = 1.078. Weight ratio = 1.078 × 1.6 ÷ 2.7 = 0.64.

Sheets with unidirectional layers inside can be stiffer than woven sheets in the main direction, so a thinner sheet may be enough. High-modulus fibers (M40 and above) also allow thinner sheets^[4]. T700 is a high-strength grade, not a high-modulus one: its unidirectional laminate is only about 4% stiffer than T300 (125 vs 120 GPa).

Carbon fiber sheet parts — CNC-cut plates: thickness sets stiffness.

Stack of carbon fiber sheets with twill finish — Standard sheets from 1 to 5 mm; custom from 0.2 to 150 mm.

Typical thicknesses by use

Use	Common thickness
Covers, trim, light brackets	0.5–1 mm
Small drone frames, camera plates	1.5–3 mm
Larger drone arms and frames, robot plates	3–5 mm
Machined fixtures and blocks	custom, up to 150 mm

Custom sheets can be made from 0.2 to 150 mm thick and up to 9000 × 3000 mm^[4].

TipIf a plate is too flexible, adding thickness is the strongest lever. If it is too heavy, cut pockets and lightening holes in low-stress areas rather than making the whole plate thinner.

What to send

Your current plate material and thickness, the size, and the load or deflection limit. We will suggest a carbon thickness and layup. Send it through the quote form, or see ordering CNC carbon sheet parts for drawings and finishes.