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Carbon Fiber Manufacturing Methods

Carbon fiber is a high-performance material with a wide range of uses in manufacturing. It is lightweight with high stiffness and tensile strength, and low thermal expansion. This makes it a good choice for use in products that need to be both sturdy and portable. There are many carbon fiber manufacturing methods, and each has its advantages and disadvantages. This post will discuss the four most common methods: wet layup, pultrusion, prepreg layup, and vacuum-assisted resin transfer molding (VARTM).

Common Carbon Fiber Manufacturing Methods

Wet Layup

In this method, carbon fibers are laid onto a mold, wetted with resin, and rolled or squeegeed to remove excess resin. The layup can be left open or a vacuum bag applied. It is then cured under room temperature or with heat and pressure to create a carbon fiber composite part. This method is commonly used for smaller volume and complex, difficult-to-mold parts.

Advantages:

  • A simple and versatile method that can be used to create parts of any size or shape.
  • Relatively low-cost, making it a good option for prototyping or small-scale production.
  • A flexible process facilitates the production of hard-to-make parts.

Disadvantages:

  • Not as efficient as other carbon fiber composite manufacturing methods, making it less suitable for large-scale production.
  • Requires skill and experience in the layup process.

Pultrusion

Pultrusion involves pulling carbon fibers through a thermoset resin bath and then through a heated die. This process aligns the carbon fibers axially and wets them with resin, creating a strong and lightweight product. Pultrusion is typically used for the production of long, straight parts such as beams, strips, or tubing.

Advantages:

  • Well suited for the production of long, straight parts.
  • A relatively efficient method, making it suitable for large-scale production.
  • Pultruded products have high bending strength and a high strength-to-weight ratio.

Disadvantages:

  • Limited to straight parts
  • Pultruded parts have low transverse strength due to the fiber orientation and can be crushed or split by a side load.

Prepreg Lay-Up

Prepreg is carbon fiber wetted with resin and partially cured, so it has the consistency of tar paper. It is cured under heat and pressure. Parts made from prepreg are strong and lightweight with higher stiffness and strength and are well suited for use in a variety of high-end applications. Prepreg lay-up is normally used for the production of flat parts such as panels or sheets, or parts with cylindrical curvature because prepreg material will not drape well over compound curvatures.

Advantages:

  • Well suited for the production of flat parts, or tubes.
  • A relatively efficient method, making it suitable for large-scale production.

Disadvantages:

  • Not well suited for the production of parts with complex shapes.
  • Prepreg is difficult to drape on a tool with compound curvature.

Vacuum-Assisted Resin Transfer Molding (VARTM) 

Manufacturing carbon fiber components with vacuum-assisted resin transfer molding (VARTM) involves placing the carbon fiber material on a tool under a vacuum bag, pulling a vacuum on the bag,  transferring the resin by vacuum into the fiber, and curing the composite under heat and pressure. This process results in strong and lightweight parts that are well suited for use in a variety of applications. VARTM is best used for the production of parts with complex geometry, such as sailboat hulls or motorcycle farings because the process allows time to carefully lay the carbon fiber in the tool before mixing and applying the resin.

Flat parts such as large sheets and plates can be molded less expensively via resin transfer, but the surface finish is not as beautiful. The individual carbon fiber tows have a flattened appearance where the texture of the individual fibers is less visible.

Advantages:

  • A preferred method to produce parts with complex geometry or very large parts.

Disadvantages:

  • A complex setup with more tooling and materials is required.
  • Not efficient for smaller simpler parts.

Choosing a Carbon Fiber Manufacturing Process

In conclusion, when choosing a carbon fiber manufacturing process it is important to weigh the pros and cons of each process. The best manufacturing method for a particular application will depend on factors such as the size and geometry of the part, the quantity to be produced, and the desired properties of the finished product, such as high tensile strength.

Working with a qualified firm that has extensive knowledge in carbon fiber manufacturing methods is imperative when embarking on a project. Element 6 is a leading expert in wet layup, pultrusion, prepreg lay-up, and VARTM, in addition to vacuum bagging, matched tooling, and other non-traditional proprietary methods.

For more information or to request a quote on a custom carbon fiber manufacturing project, please send us an email or give us a call at 315-252-2559.