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Fibre Tressée Understanding T700 carbon in sports rackets

Tensile strength and modulus: two notions you should not confuse

Published on October 30, 2026 Reviewed October 30, 2026 4 min read

Text by the Fibre Tressée editorial team.

A carbon strand stretched between two clamps in a testing workshop, seen up close.
Break or flex. Tensile strength indicates the stress a fiber withstands before it breaks. Modulus indicates how much it deforms under load. These two values are independent: a fiber can be very strong without being very stiff. Datasheets express these values in megapascals and gigapascals, sometimes in imperial units.

This article, “Tensile strength and modulus: two notions you should not confuse,” proceeds in announced stages, and I will outline its thread from the start. Learn to tell what breaks a fiber from what makes it stiff.

At the outset: The Laws of Badminton limit a racket to 680 mm in overall length and 230 mm in width, and the strung area to 280 mm by 220 mm, but they do not impose any material: the “T700 carbon” label is the manufacturer's choice, not a regulatory requirement. Toray presents the T700S as a standard modulus fiber with high tensile strength, with processing characteristics suited to filament winding, weaving and prepreg. Toray T700S carbon fiber has a tensile strength of 711 ksi, or 4,900 MPa.

The definitions to keep close at hand

Let us take the time to name precisely the notions we will be handling.

Intermediate modulus fiber

A category of carbon fibers that are stiffer than standard modulus fibers, but less stiff than high modulus ones.

As an illustration, Toray's page on standard, intermediate and high modulus fibers makes it possible to compare these categories.

For the full definition, see the entry Intermediate modulus fiber.

Shaft

The part of a badminton racket that connects the handle to the head.

To make the notion tangible, the Laws of Badminton name the shaft among the components of the racket.

You will find the detail in the entry on Shaft.

Stringbed

The area of a badminton racket occupied by the strings, intended to strike the shuttlecock.

To illustrate, the Laws of Badminton specify that the strings form a defined surface within the head of the racket.

To clarify this term, open the entry Stringbed.

The mechanisms up close

Here is the basic principle to keep in mind: Toray explains that sizing improves handling and compatibility with the resin; a small amount helps the fiber spread out, while a larger amount suits demanding manufacturing environments. Use this principle as a framework for what follows.

At the heart of the method lies this: Toray describes the T700S as a “never-twisted” (without twist) fiber, designed to offer good characteristics for filament winding, weaving and prepreg. Note this foundation before moving on.

Let us first set down this principle: Toray presents standard modulus as the most economical category of carbon fiber in its range. Come back to this idea whenever a doubt arises.

Let us begin with the foundation: the T700G is a variant of the T700S with enhanced fiber-resin adhesion; Toray intends it notably for aerospace and sporting goods.

First steps

Keep this methodological tip in mind: the home page of the Fédération Internationale de Padel (FIP) does not detail the permitted dimensions or materials of palas (padel rackets); these requirements are found in its regulatory documents, which you should consult directly.

Mistakes to avoid

Let us flag this danger: a standard modulus fiber is not the stiffest; intermediate modulus (42 MSi) and high modulus (up to 85.3 MSi) fibers exist, so “T700” is not synonymous with maximum stiffness. Note this point of caution for what follows.

What is the difference between strength and modulus?

Let us look at what happens here: the T300 is Toray's reference fiber, used in aerospace for more than 20 years; the T700 belongs to the same standard modulus family.

The figure to remember: at Toray, standard modulus fibers have a modulus of about 33-34 MSi or slightly higher; this family includes the T300, T700S and T700G.

Let us pause on this measurement: Toray's T700S is offered in tows of 6K, 12K and 24K, that is, about 6,000, 12,000 or 24,000 filaments per tow.

Which units will you encounter?

Keep this fundamental rule in mind: a carbon fiber is a filament about 5 to 10 micrometers in diameter, made up mostly of carbon atoms, with high stiffness and high tensile strength relative to its weight. Use this principle as a framework for what follows.

Let us rely on this verified value: Toray's M series (M35J to M60J) covers moduli from 49.8 to 85.3 MSi (343 to 588 GPa); the T700, at 33.4-34.8 MSi, therefore sits in the lower part of the stiffness scale of Toray carbon fibers.

To finish, in practice

Reread the parts that struck you most, pencil in hand, before deciding.

Related reading

Sources cited

Sources and verification

  • This text rests on 6 sources: 2 official bodies or institutions and 3 manufacturer documentations.
  • Facts checked against their sources on October 13, 2026.
  • How sources are chosen and verified: Fact checking.