Carbon prepreg refers to carbon fibers (in unidirectional lamina or woven forms) that are pre-impregnated with a polymer resin, usually epoxy. The term "prepreg" originates from "pre-impregnated." Prepregs are available in standard widths ranging from 3 to 50 inches (76 to 1270 mm). Depending on whether the polymer matrix is thermoset or thermoplastic, prepregs are stored either in a refrigerator or at room temperature. Composite structures can be formed by manually or mechanically laying prepregs in different orientations. Subsequently, parts are manufactured through vacuum bagging and curing processes under high pressure and temperature.

^{Carbon fabric and resin}

Carbon prepregs are widely used in high-performance composite applications. Due to their superior mechanical properties and ease of production, they are preferred in critical industries such as aerospace, automotive, and defense. However, their cost and storage requirements limit their use to specific applications.

Carbon Prepreg Manufacturing

^{Resin Impregnation of Carbon Fibers}

A series of fibers is passed through a resin bath. Afterward, the resin-impregnated fiber structure is heated to promote the curing reaction (transitioning from phase A to phase B). Thermoset resins have three phases: A, B, and C. Resins are manufactured in phase A, where the resin can be solid or liquid but can flow when heated. Phase B is the intermediate stage during which prepreg is produced with thermoset resin, facilitating the easy handling of composite layers like graphite/epoxy. Phase C is the final stage of the thermoset resin reaction, occurring during the curing process of composite layers to produce parts.

Heat and pressure are applied during phase B to partially cure the resin, resulting in a tacky prepreg that can still be processed. Once cured in phase C, the process becomes irreversible, creating a hardened, insoluble structure. Phase B prepreg is wound onto a roll, and a release film is applied to prevent prepregs from sticking together during storage.

Structure of Carbon Prepreg

• Fiber: Carbon fiber serves as the primary load-bearing material. The fibers can be arranged in woven fabrics or unidirectional tapes.
• Resin: Thermoset resins such as epoxy, phenolic, or others are used. The resin is uniformly pre-applied to the fibers.

Usage of Carbon Prepreg

Prepreg material is placed into molds and arranged to match the desired shape. It is then cured (hardened) in an autoclave or a pressurized oven. During this process, heat and pressure are applied to complete the polymerization of the resin, resulting in an extremely durable composite structure.

Features and Advantages of Carbon Prepreg

• High Strength and Stiffness: Combines the natural strength of carbon fiber with the binding properties of the resin.
• Homogeneity: Pre-applied resin ensures consistent mechanical properties during production.
• Ready to Use: Prepreg eliminates the need for resin mixing or fiber arrangement during manufacturing, simplifying the process.
• Precision: High precision in resin ratio, fiber density, and layer arrangement.
• Superior Mechanical Performance: Offers high strength, stiffness, and durability.
• Time-Saving: Speeds up the production process as no resin mixing or application is required.