Carbon Fiber Tow Strength vs Woven Fabric Strength 

Why Carbon Fiber Tow Strength Is Not the Same as Woven Fabric Strength

Carbon fiber is widely known for its exceptional tensile strength and stiffness.
But many engineers and buyers are surprised when they discover that carbon fiber tow and carbon fiber fabric do not have the same mechanical properties—even though they are made from exactly the same raw material.

Why does the strength of a carbon fiber fabric drop compared to the strength of the tow it is made from?
The answer lies in fiber alignment, textile structure, and how load is transferred through the material.

This article explains the fundamental reasons behind the difference between tow strength and woven fabric strength—an essential concept in composite materials engineering.

1. What Is Carbon Fiber Tow?

Carbon fiber tow is a bundle of thousands of continuous, parallel carbon filaments (e.g., 3K, 6K, 12K, 24K).

Characteristics of tow:

• perfectly straight fibers

• no bending or waviness

• full alignment in the load direction

• individual filaments all share the load

• maximum utilization of carbon fiber strength

Because of this perfect alignment, tensile testing on tow represents the highest mechanical performance the fiber can achieve.

2. What Changes When Tow Is Woven Into Fabric?

When a carbon fiber tow is transformed into plain, twill, or satin fabric, its structure fundamentally changes.

These fabrics require the yarn to interlace in two directions (warp and weft), which introduces:

• fiber bending

• periodic up-and-down movement

• crossover points

• slight separation of filaments

• changes in local fiber volume fraction

These structural modifications reduce the ability of the fibers to share load efficiently.

3. Fiber Crimp: The Primary Reason for Strength Reduction

The most important factor is fiber crimp.

Crimp refers to the wavy shape that fibers take as they weave over and under each other.
Unlike a straight tow, woven yarns are no longer perfectly aligned with the direction of loading.

Even small misalignment angles (2–10°) can significantly reduce tensile efficiency, because carbon fiber is extremely sensitive to off-axis loading.

Tow:

• straight

• all fibers aligned

• optimal tensile load transfer

Woven Fabric:

• crimped fibers

• some fibers out of plane

• uneven local stress distribution

This explains why woven fabric cannot achieve the same tensile strength as the original tow.

4. UD (Unidirectional) Fabric Retains High Strength

UD fabrics or tapes have:

• 100% fibers aligned in one direction

• minimal crimp

• straight load paths

As a result, UD materials retain a much higher percentage of the original tow’s performance and are suitable for:

• aerospace structures

• sporting equipment

• wind turbine blades

• drones and UAV components

 5. Spread Tow Fabric: Boosting Woven Strength and Lightweight Performance

Spread Tow Fabric is an advanced form of woven carbon fiber fabric designed to reduce crimp and improve fiber utilization:

How it works: carbon fiber tow is flattened and spread into thin, wide tapes before weaving

Advantages:

• • Fibers remain more straight → higher tensile efficiency

  • Reduced crimp → closer to UD performance in the load direction

  • Lightweight → fewer layers or lower fabric weight needed for the same strength

Applications: aerospace, high-end sports equipment, drones, and other lightweight composite structures

Spread Tow fabric is essentially a bridge between conventional woven fabric and UD tapes, offering better strength and stiffness than regular woven fabrics while retaining drapability and handling.

6. Summary: Tow Strength ≠ Fabric Strength

Understanding the difference between tow and woven fabric strength is essential in composite design.

✔ Tow provides maximum fiber strength
—because fibers are perfectly straight.

✔ Woven fabric reduces strength
—due to crimp, misalignment, and yarn interaction.

✔ UD materials retain the highest structural performance
—making them suitable for high-load, directional applications.

✔ Spread Tow fabrics combine the advantages of woven and UD materials
—reducing crimp and improving strength while maintaining drapability and lightweight design.

Choosing the right form of carbon fiber depends on your design priorities:
strength, stiffness, drapability, appearance, impact resistance, or lightweight performance.
There is no “best” form—only the best choice for your application.

Conclution

If you are working on a composite project and want guidance on:

• selecting the right carbon fiber form (tow, UD, or woven),

• understanding mechanical performance differences,

• or choosing materials for structural vs. aesthetic applications,

our technical team is happy to help.

👉 Contact us to get free material recommendations, datasheets, or custom fabric options for your project.
We are here to support your development with practical, engineering-driven advice.