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Carbon fiber rovings are a highly cost-effective resource for creating preforms. The reason for this is the fact that they are the least costly raw material and significantly reduce the amount of resources wasted during preforming. In addition, carbon allows for the creation of composite parts featuring structural integrity superior to steel at roughly a fifth of the weight. To effectively use these fibers for preforming, it is necessary to include a matrix material for binding. While pure rovings need to be injected with epoxy after being shaped, prepreg composites make this additional step entirely unnecessary, resulting in a quicker and more precise manufacturing process.
The proper Binding
Carbon, fiberglass or basalt filaments do not adhere to each other naturally, which is why it is absolutely necessary to employ some form of adhesive compound when using fiber materials to create layups. Epoxy is perhaps the most frequently used adhesive binder in industrial manufacture. After shaping the composite, this binder is then injected between the shaped fiber layers and heat-treated. This creates a chemical reaction which causes the binder material to harden into the preform shape.
Prepreg fibers are already pre-impregnated with resin. This has several advantages over the injection procedure, including:
- More precise shaping of the preform
- Shaping into forms too complex for injection molding
- Easy storage of prepreg composites for quick access later
Because of these advantages, prepregs are often more convenient for shaping and curing, allowing for faster application and reducing the time necessary for the production of high volumes of preforms by eliminating the time required for epoxy injection.
How to handle Prepreg Materials
Since prepreg fibers are already saturated with resin, the actual chemical reaction that turns the binder into solid polymer has already begun. Any additional energy in the form of heat, pressure or radiation will accelerate the process. For this reason, prepreg and towpreg products cannot be stored indefinitely. To prevent them from hardening prematurely, it is generally recommended to only store them at low temperatures.
This makes prepreg composite ideally suited for creating quick and cost-effective complex shapes with a pre-determined amount of material, making long storage unnecessary.
Prepreg Composites allow for easier Planning and Layup
Pre-impregnated fibers have the distinct advantage of being able to shape layups, which can then be cured directly by simply applying heat. The advantages of this system are self-evident – prepreg layups can be cured and shaped without the need for the elaborate and time-consuming additional step of injecting epoxy resins.
Pre-impregnated composite materials cannot be used with all manufacturing processes for which non-impregnated materials can be used. However, the patented Compositence manufacturing process is able to apply pure rovings as well as prepregs.
This has the effect of simplifying the manufacturing process significantly. An appropriate amount of materials can be acquired prior to layup, requiring neither the purchase of an additional amount of resin nor the additional step of combining the two elements during manufacture. This makes manufacture using prepregs noticeably easier to plan for as well, as prepreg fibers constitute a slightly larger investment into the more costly raw material, while significantly decreasing the amount of material wasted during the process of combining fibers and resin during preforming.
Saving Time and Money while preforming complex shapes
Prepreg fiber is a fundamental resource for industrial-scale Automated Fiber Placement processes. By having rovings pre-impregnated, preform manufacturers can save time and costs, leading to higher production turnout. Additionally, the highly cost-efficient patented Compositence manufacturing process can use prepregs as well as pure rovings and thus allows for extreme flexibility.