Carbon Fiber Composites: How Are They Made?
Carbon fiber, epoxy, or another kind of resin, and sometimes metal, are used to create carbon fiber composites. The necessary qualities and intended usage heavily influence how they are created. Depending on the needs, they can be produced as unidirectional, bidirectional, or quasi-isotropic materials in various forms and sizes. Filament winding, pultrusion, matching tooling, resin transfer, and autoclave processing are all involved in carbon fiber parts manufacturing.
In this blog post, we’ll explain carbon fiber composites and briefly go over how they’re made.
Carbon Fiber Composites: What Are They?
Carbon fiber is a stranded material made up of thousands of tiny graphite fibers. It is made of a lightweight yet very strong material. Carbon fiber composites are a great production material for many components because they have around 60% the strength and stiffness of steel at 20% the density and roughly 1.7 times the strength and stiffness of aluminum at 56% the density. Because of their high stiffness and strength-to-weight ratios, as well as the ability to adjust physical qualities in certain places and orientations inside a product, carbon fiber composites are the material of choice for engineers and designers when it comes to demanding applications.
The Advantages of Carbon Fiber
The advantages of carbon fiber composites are many. They could be stronger than other materials, which is one advantage. Additional advantages of carbon fiber include:
- High tensile strength to weight
- High stiffness to weight
- X-ray translucency
- Low thermal expansion
- High chemical resistance
The Making of Carbon Fiber
Carbon fiber is a chemical-mechanical composite. Long fibers are extracted and heated without oxygen to avoid burning. This produces carbonization, removing non-carbon atoms.
The fibers are heated in specialized atmospheres, producing chemical interactions between molecules and converting them into carbides that strengthen and increase conductivity. Process details vary by product’s quality and purpose. After this procedure, the fibers can be used in sportswear, equipment, and vehicle components.
Processes for Fabricating Different Carbon Fiber Composites
Multiple techniques can make carbon fiber components. Some procedures, like injection molding, work with various materials, while others focus on carbon fiber composites. Process choice depends on composite materials, component design, and application. Budget and volume should also be considered. Most carbon fiber fabrication includes molding the composite into the final shape. Molding tools and complexity vary.
Open Molding
Fiberglass composites are typically made via open molding. Hand layup or spray-up can be used for open molding, spraying catalyzed resin and chopped fibers into the mold simultaneously during the spray-up process.
Hand Layup and Vacuum Bagging
Hand layup includes hand-laminating dry carbon fiber cloth or prepreg composites onto a mold. Dry fabric is coated with resin between each ply, then debulked using hand rollers or vacuum-bagging. Debulking eliminates air trapped between layers that can produce voids and weaken the part.
Resin-Infused Carbon Fiber Fabrication
While the spray-up procedure reduces VOCs, rising restrictions in the US and EU limit worker exposure to dangerous air pollutants. Faster manufacturing has led to more automated carbon fiber fabrication techniques. Several resin-infused carbon manufacturing methods exist.
Resin-transfer molding (RTM) uses a metal or composite two-part, closed mold. Close the mold after adding dry reinforcement. Measure blended low-viscosity resin is poured into the mold using injection ports.
Vacuum-assisted resin transfer molding (VARTM) draws resin into the mold without pressure. This technique doesn’t need high pressure or heat. VARTM’s low-cost tooling allows for the creation of larger, more complicated components.
High-Volume Molding Techniques
Compression molding is a high-volume thermoset molding technique often used for large-scale production runs. Usually, this method makes use of expensive but reliable metal tools. On a series of steel dies, sheet molding compound (SMC), a composite material generally consisting of chopped fibers layered between sheets of thick resin paste, is pressed. The SMC is assembled on a heated mold after it is prepared for molding, after which it is closed and clamped, and high pressure is then applied. The SMC flows to fill the mold cavity as the material’s viscosity decreases.
Injection molding is perhaps the fastest, highest-pressure, lowest-volume, closed molding technique. Thermoplastics are the materials with which it is most often employed, although automated injection molding of bulk molding compounds (BMC) has grown in popularity over time. During the BMC injection molding process, a ram or screw-type plunger pushes a set amount of material into a heated, closed mold.
There are several other high-volume molding techniques for making carbon that combine these two processes or other related techniques. Pultrusion, automated fiber placement (AFP), tube rolling, filament winding, automated tape laying, and automated tape laying (ATL) are other high-volume molding methods.
Additive Manufacturing
A 3D object is produced automatically by additive manufacturing, often known as 3D printing, from many 2D cross-sectional layers. Computer-aided drafting (CAD) solid models are the foundation of all additive manufacturing processes. The model is then cut into thin 2D cross-sectional patterns using special software. The software tells the 3D printer how to stack the 2D slices to make a real 3D object.
Depending on the features of the 3D printer, various materials are now used in 3D printing. Stereolithography (SLA), fused deposition modeling (FDM), selective laser sintering (SLS), digital light processing (DLP), and PolyJet printing are examples of additive manufacturing techniques that are often used today. The best option for fabricating carbon fiber is FDM since it is the technique most often used for fiber-reinforced plastics. No matter what technique is used, 3D printing is often used to make prototype tools. This makes a part easy to check for shape, fit, and sometimes testing.
The number of components that need to be made, your spending limit, and your parts’ use will ultimately play a significant role in determining the optimal carbon fiber production process for your project. While certain carbon fiber fabrication techniques can be done on your own, others require the engagement of a qualified carbon fiber fabricator. When you understand the different ways carbon can be made, it’s easier to choose the best method for your application.
Conclusion
Carbon fiber composites are a great material for making many of the parts that carbon fiber manufacturing companies use. This is because they can have different physical properties depending on where the carbon fibers are placed in the finished product. How each part is made depends on how stiff or strong it needs to be, and in the end, this process comes down to how the finished product will be used.
