Pre-impregnated materials (prepregs) are utilized in high-performance applications when weight and mechanical properties are top priority. Manufacturers from the aerospace, transportation, and sustainable energy industries benefit from pre-impregnated material properties. Advanced fibers such as carbon fiber and aramid with high-quality epoxy resins are the most common materials used in prepreg structures. By combining these two materials together, the finalized reinforced structure will encapsulate properties from the initial independent materials.
“Prepreg” is the common term for a reinforcing fabric which has been pre-impregnated with a resin system. This resin system (typically epoxy) already includes the proper curing agent. As a result, the prepreg is ready to lay into the mold without the addition of any more resin. In order for the laminate to cure, it is necessary to use a combination of pressure and heat.
Prepregs Made from Thermoplastic or Thermoset Resin
Prepregs are typically used by experienced fabricators who are interested in minimizing the weight on their part. Typical applications include aerospace, racing, sporting goods, pressure vessels, and commercial products.
Generally, prepregs are used by fabricators who have experience with hand layup and vacuum bagging. Although it is possible for a beginner to tackle prepreg to avoid the pitfalls of hand layup, it is typically not done.
Thermoplastic Resin: Most commonly used to produce bottles, packaging containers, toys, appliances, electronics housings, automotive interiors, and much more. The addition of glass and carbon fiber allows for a much higher strength and reinforcement. An advantage of utilizing thermoplastic resins is the ability to reheat and reform the material numerous times.
Thermoset Resin: Most commonly used for sealed products due to its high resistance to deformation. Thermoset resins allow for an improvement of the mechanical properties of the composite by providing a higher resistance to harsh chemicals, extreme temperatures, and an overall improvement of integrity.
Removal of Excess Resin from Prepreg Reinforcement
One of the most advantageous aspects of replacing inefficient materials with prepregs is that the manufacturing process produces far less waste. The resin impregnation process precisely controls the fiber-to-resin ratio as well as ply thickness. After the fabric has been injected with the resin, excess materials are removed from the structure. During this time, the reinforcement undergoes partial curing, which is known as the B-Stage.
Prepreg Curing with Low and High Temperatures
Another added benefit of developing prepreg reinforcements is that these structures require less time for curing. As the B-stage of the process initiates, prepregs require refrigerated storage in order to cure. After a short period in refrigerated storage, the curing process is then activated by applying heat and pressure from heating tools such as an autoclave. Thermoset and thermoplastic prepregs create durable, lightweight composite structures suitable for an array of applications.