Carbon Fiber Types

One of the most distinctive aspects of carbon fiber is the wide range of variations available. Each type offers specific characteristics, giving engineers a broad set of options when selecting the right material for a project.

There are several ways to categorize the different carbon fiber fabrics that exist.

In this article, we’ll explore the different types of carbon fiber and the properties that set them apart. When we refer to carbon fiber, we often mean a carbon-fiber composite—fiber combined with resin and cured. However, covering every possible composite configuration would make this article far too long, so we will focus exclusively on the types of raw carbon fiber, without considering resin systems.

Classification by Precursor Material

One of the most common ways to categorize carbon fibers is by the precursor from which they are produced. Today, two main precursor families dominate the industry.

Polyacrylonitrile (PAN)

PAN is the dominant precursor, accounting for roughly 90% of commercial carbon fibers. It is valued for its high carbon yield and excellent mechanical performance, which have made it the industry standard. PAN can be used as a homopolymer or a copolymer, often with additives that enhance processing and improve final fiber properties.

Pitch

Pitch-based carbon fibers are produced from petroleum- or coal-derived asphalt. They are mainly used when extremely high performance is required, as this precursor allows the production of fibers with very high modulus and exceptional thermal stability. While less common than PAN-based fibers, pitch-derived fibers excel in applications demanding the highest stiffness levels.

Rayon

Rayon was the first precursor used to produce carbon fibers in the 1950s and 1960s. It originates from a cellulosic source, typically dissolving pulp. Although it has largely been replaced due to its lower carbon yield and higher cost, it remains historically significant as the origin of carbon-fiber technology.

Plain weave carbon fiber fabric. It’s not only about aesthetics, every type of carbon fiber fabric has specific mechanical characteristics. Photo credit: Hadhuey.

Classification by Mechanical Properties

The two primary mechanical properties used to distinguish one carbon fiber from another are tensile strength and tensile modulus. Tensile strength is the maximum force a material can withstand while being pulled or stretched before breaking or becoming permanently deformed.Tensile modulus measures a material’s stiffness—its resistance to stretching or deforming under tension.

These metrics are essential for achieving the desired mechanical performance and can vary widely between fiber types. A common classification system groups fibers according to their elastic modulus, resulting in five categories.

Low Elastic Modulus

• Tensile modulus ≤ 200 GPa
• Tensile strength ≤ 3500 MPa

Standard Elastic Modulus

• Tensile modulus: 200–275 GPa
• Tensile strength: 2500–5000 MPa

Intermediate Elastic Modulus

• Tensile modulus: 275–350 GPa
• Tensile strength: 3500–8000 MPa

High Elastic Modulus

• Tensile modulus: 350–600 GPa
• Tensile strength: 2500–5000 MPa

Ultra-High Elastic Modulus

• Tensile modulus: 600–950 GPa
• Tensile strength: 2500–4000 MPa

Classification by Form

Another essential factor when choosing a carbon fiber is its form, since this determines how it can be used. Because carbon fiber is anisotropic, the orientation of its filaments greatly influences the material’s mechanical behavior.

Unidirectional Tape

An arrangement of continuous fibers aligned in the same direction. This provides extremely high tensile strength along that orientation and allows engineers to tailor mechanical performance based on fiber direction and the number of layers used.

Fabric Forms

Carbon-fiber fabrics are created by interlacing fibers, just like any textile. Different weave patterns result in different properties. These are the three most common types:

Plain Weave

Plain weave interlaces fibers in an alternating over-under sequence, forming a simple checkerboard-like pattern. It offers balanced strength in multiple directions, excellent dimensional stability, and easy handling—ideal for flat or gently curved surfaces. However, it is not the best option for highly complex geometries.

Twill Weave

Twill weave typically appears in 2×2 or 4×4 patterns. In a 2×2 twill, each tow passes over two and under two; a 4×4 follows the same principle with four. This produces the fabric’s characteristic diagonal pattern. Twill is more pliable and drapes better over complex shapes while maintaining good stability, though it requires more careful handling to avoid distortion.

Satin Weave

Satin weaves provide excellent drapability and easily conform to complex contours, though they are less stable than plain or twill weaves. Common variants include 4HS, 5HS, and 8HS, where the tow passes over several tows and under one (3/1, 4/1, and 7/1 respectively). Higher harness numbers improve drape but reduce stability.

Chopped Fiber

With the increasing popularity of forged carbon fiber, another available format is chopped fibers or short strands. This material adapts easily to complex molds, though forged carbon exhibits mechanical behaviors different from traditional continuous-fiber composites. If you want to learn more about the strengths and applications of forged carbon fiber, we recommend this article where we analyze its unique advantages.

Forged carbon fiber partial cover for a Lamborghini engine bay.

Classification by Tow Size

Carbon-fiber filaments are extremely small—typically 5–9 microns in diameter. Before weaving, they are grouped into bundles called tows. A common way to describe fabric weight or thickness is by specifying the number of filaments per tow.

A 3K fabric is made with tows of 3,000 filaments per tow. A 6K fabric is composed by tows with 6,000 filaments per tow, and a 12K fabric contains tows made by 12,000 filaments each. Tow size directly influences fabric appearance, weight, and handling characteristics.

TL;DR

Carbon fibers come in many types, defined mainly by their precursor (PAN, pitch, or rayon), their mechanical performance (from low to ultra-high modulus), their form (unidirectional tape or woven fabrics like plain, twill, and satin), and their tow size (3K, 6K, 12K, etc.). PAN is the standard precursor, pitch is used for the highest-stiffness fibers, and rayon is historically significant. Fabric weave and tow size determine drape, stability, and final part behavior, while chopped fiber enables forged-carbon applications.