The benefits of prepregs
Prepregs are nowadays widely used in areas were high quality properties are requested due to the wide range of advantages the operator can achieve with them. Prepregs are produced via machines which means the quality is stable, traceable and repeatable. Especially a stable and repeatable quality is necessary whenever the part design is very sensitive regarding key quality parameters like fiber volume content. With prepregs you achieve the best balance between fiber / resin ratio and the most optimum fiber volume content. Another key benefit of prepregs is the combination of resin and fibers where operators can apply these layers in one step. The workload will be reduce by far compared to infusion process for example where fibers need to be placed first and injected with resin in a second step.
Areas of prepreg application
Prepregs are used in the aerospace industry, where the demand for carbon fiber continues to increase. Especially carbon fiber prepregs have been used in the airframe of the Airbus fleet for more than 20 years. Prepregs are also used in the automotive industry, for medical applications such as orthotics and prosthetics, and in rotor blades of wind turbines. In electrical engineering, prepregs are deployed as an intermediate layer in multilayer circuit boards and as insulating material for electrical machines and transformers.
Prepreg matrix systems
The matrix or resin systems of a prepreg are distinguished according to their hardening temperature and the type of resin. The curing temperature greatly influences the glass transition temperature and thus the operating temperature of the complete part. The matrix consists of a mixture of resin, hardener, and in some cases additives like accelerators and particle toughening. Due to the fact that the matrix is reactive, most of the prepregs needs to be stored at frozen conditions to keep their shelf life. To start the reaction between the resin and the hardener, temperature is applied within an autoclave, press or oven to the system. At a certain temperature the cross-linking between the resin and hardener part starts which will end up in a fully cured system after a certain time.
Prepreg resins types
Several resin types are available today on the market. Epoxy resins due to their good cost/performance balance are most widely used. Further systems like Phenolics, Bismaleimide, Cyanate Ester and Polyimide are also commonly available.