I. Fiber Tow Mechanical Properties (Typical Values)
| Grade | Tensile Strength (MPa) | Tensile Modulus (GPa) | Elongation at Break (%) | Density (g/cm³) | Tow Size |
|---|---|---|---|---|---|
| T300 | 3 530 | 230 | 1.5 | 1.76 | 1K–12K |
| T700S | 4 900 | 230 | 2.1 | 1.80 | 6K–24K |
| M40J | 4 400 | 377 | 1.2 | 1.77 | 6K–12K |
Interpretation:
- T700 offers ≈ 38 % higher strength than T300 at the same modulus → pure “high‑strength” upgrade.
- M40J’s strength lies between T300 and T700, but its modulus is over 60 % higher → classic “high‑strength, high‑modulus” route.
- T700 has the highest elongation; M40J is the most brittle.
[caption id="attachment_1909" align="aligncenter" width="472"]
Carbon fiber material[/caption]II. Epoxy‑Matrix Unidirectional Laminate Performance
(55 % fiber volume fraction, typical values)
| Property | T300/EP | T700/EP | M40J/EP |
|---|---|---|---|
| 0° Tensile Strength (MPa) | 1 500 | 1 800 | 1 650 |
| 0° Tensile Modulus (GPa) | 135 | 135 | 220 |
| 0° Compressive Strength (MPa) | 1 200 | 1 400 | 1 000 |
| Interlaminar Shear Strength (MPa) | 90 | 95 | 76 |
Interpretation:
- In composites, T700 still shows clear strength benefits, but its modulus matches T300.
- M40J lamination delivers over 60 % higher modulus, yet compressive and shear strengths drop 20–30 % → consider thicker or hybrid layups when designing.
III. One‑Sentence Application Summary
- T300: Civil drones, automotive upgrades, sporting goods—best value.
- T700: Primary structural components, pressure vessels, high‑end bicycles—balanced weight and strength.
- M40J: Satellite frames, optical platforms, precision robots—ultra‑stiff with low deflection; watch for brittleness and cost.
IV. Selection Tips
- Pure Strength First: T700 > T300 > M40J
- Stiffness Priority: M40J leads by a wide margin
- Cost‑Sensitive: T300 is 60–70 % the price of T700; M40J is 2–3× the cost of T700
Source Link: https://www.cnccarbonfiber.com/engineering-hub/design-guide/carbon-fiber-t300-vs-t700-vs-m40j.html