Understanding Carbon Fiber Fabrics

Carbon fiber fabrics, akin to traditional textiles like cotton and nylon, are crafted from continuous carbon fiber filaments. These filaments are bundled into tows, classified by the number of filaments they contain (e.g., 3k for 3,000 filaments). Unlike typical fabric threads spun from short fibers, carbon fiber fabric consists of long, continuous filaments. By laminating these fabrics with a resin matrix, strong and lightweight composite materials are produced, suitable for diverse applications from aerospace to sports equipment.

The strength and stiffness of the composite largely depend on the orientation of these fibers, significantly influencing their mechanical and thermal characteristics. Aligning more fibers in the direction of the applied load enhances the material’s properties in that orientation. Thus, a composite with randomly oriented fibers, such as a chopped nonwoven, will generally have lower stiffness compared to a woven fabric with fibers aligned parallel to the load.

Carbon fabric-reinforced polymer composites are extensively utilized in the production of various aeronautical components, such as flaps, ailerons, and landing-gear doors, among other items used in the aviation sector. Beyond aerospace, these composites find applications in several other fields, including residential building, maritime, automotive, and sports industries.

The term “carbon fiber fabric” broadly encompasses various forms of textiles made from carbon fibers and are categorized based on their weaving or arrangement patterns, including woven, non-woven, and unidirectional arrangements, each offering unique properties and applications.

Types of Carbon Fiber Fabrics

  • Unidirectional Carbon Fiber: In this form, all carbon fibers run in the same direction. It offers high strength in the direction of the fiber alignment but requires layering in various orientations to achieve multidirectional strength.
  • Woven Carbon Fiber: This is the most common type and is made by weaving carbon fibers in various patterns (like plain, twill, or satin), resulting in a fabric that is strong in two dimensions and has a distinctive aesthetic appearance.
  • Non-Woven Carbon Fiber: This type involves randomly orienting the carbon fibers or aligning them in a mat form without a specific weave. It is used in applications where uniform strength is needed in all directions without the structural requirements of a weave. They offer uniform properties in all directions but generally have lower mechanical properties compared to woven fabrics. However, non-wovens can be engineered to meet specific performance criteria for certain applications, and their isotropic nature can be an advantage in applications requiring uniform properties in all directions.

Unidirectional Carbon Fiber

Unidirectional (UD) carbon fiber fabrics are designed with all fibers aligned in a single, parallel direction, enhancing the strength and stiffness in that specific orientation. This strategic arrangement of fibers is crucial for applications where maximum strength is required along a particular axis, such as in the direction of motion for airplanes. Found in forms like non-woven fabrics, UD prepregs, and unidirectional plies within composites, these materials are integral to manufacturing carbon fiber composite parts for various real-life applications. 

The composition of UD fabrics often involves a significant proportion of carbon fibers aligned in the warp direction, complemented by a resin binder or secondary materials that serve to bind the fibers together. This setup is pivotal for creating UD carbon fiber tapes and fabrics that provide localized or structural reinforcement in a wide array of applications, offering a tailored approach to leveraging carbon fiber’s inherent strengths and properties.

Woven Carbon Fiber Fabric

Woven carbon fiber is a network of interlacing fiber tows. Raw carbon fiber from tows (or yarns) is woven together to make carbon fiber fabrics (or carbon fiber cloth). These varying densities of carbon fiber will determine the strength and, therefore, the final fabric or composite application. 

The carbon fiber tows are identified as ‘warp’ and ‘weft.’ The weft tows (or fillings) are inserted over and under the warp tows, making “weaves.”

Woven carbon fiber can be bi-directional (or bi-axial) or multi-directional. Bidirectional woven carbon fiber has fibers oriented in two different directions, generally in perpendicular warp and weft directions, at 0° and 90°. 

Carbon fiber tows are woven together in horizontal and vertical directions and can, therefore, sufficiently hold the fabric together. However, the edges still need to be kept intact, and can use some binding materials where needed. This type of orientation of carbon fibers gives the resulting fabric or composite a lower overall strength in any one direction but a much more balanced strength in all directions.

Woven carbon fiber fabrics are available in many different patterns, such as plain, twill, and satin weaves, with varying drapability and handleability characteristics. Crimping differs slightly with each weave. A plain weave with higher stiffness will be more flexible and, therefore, less stiff comparatively. 

The drape of the fabric will depend on the weave type (or the interlocking fibers). They can be molded to fit complex curvatures while maintaining their desirable properties. Twill weaves, for example, will be more fragile than plain weaves with more cross-sectioned fibers. But at the same time, twill weave carbon fibers are able to follow contours more effectively than plain weaves.

Woven carbon fibers are then impregnated to create ‘plies’ and are further layered and cured to make ‘composites.’ Woven carbon fiber composites are prepared by infusing these woven fabric lay-ups with compatible resins. 

Woven carbon fiber fabrics are preferred over unidirectional carbon fibers in applications where drapability and convenience of manufacturability are critical. In most structural strengthening applications, woven carbon fiber fabrics are laminated on-site to prepare composites for repairs. Woven reinforcements can withstand tension in all directions while adding a little volume to the original structure and are also preferred due to their waterproofing characteristics. Other high-performance applications of woven carbon fiber are found in the aerospace (fuselage, rudders, etc.), automotive such as motorcycle parts, medical, sports (skis, rackets), marine, and military industries.

Non-woven Carbon Fiber Fabric

In carbon fiber non-wovens, the fibers are randomly distributed in a two-dimensional plane, are not woven together in the traditional sense of textile production, and are only bonded together through the use of a resin, binder, or mechanical interlocking. 

Therefore, the performance of non-wovens tends to be equal in all directions, indicating their isotropic nature. Non-woven fabrics do not undergo the complications of a weaving process and are manufactured by air laying, carding, and meltblasting. However, their performance is difficult to predict because of fluctuations in the properties of randomly distributed carbon fibers. Although they are lightweight, it is not exactly to force them out of their shape

Non-woven carbon fiber fabrics are used in applications where uniform strength across all directions is needed or where the fabric will be combined with other materials to form a composite material. 

The described fabric forms, including wovens, non-wovens, and unidirectional (UD) types, are available either as ‘dry’ materials or as resin-impregnated (prepreg) materials. These prepreg sheets can then be precisely aligned, stacked, and exposed to heat and pressure, a process that triggers a chemical reaction resulting in the curing and hardening of the composite material.

Fairmat offers recycled CFRP Chips, available in both unidirectional and bidirectional forms, representing a leap forward in material design, offering product designers and engineers a sustainable, high-performance option. These Chips are made entirely from recycled carbon fiber composite, aligning with modern demands for eco-friendly materials without sacrificing the mechanical properties essential for high-stakes applications.

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