Preimpregnation

Preimpregnation, often shortened to "prepreg," refers to a composite material manufacturing process where reinforcing fibers are pre-impregnated with a resin matrix. This means the fibers, such as carbon fiber, glass fiber, or aramid fiber, are already coated with a partially cured resin system, typically a thermoset like epoxy. The resin is usually applied in a liquid or semi-solid state and then partially cured to a B-stage, making it tacky but not fully hardened.

The prepreg material is then supplied in sheets or tapes, often protected by backing paper or film to prevent premature curing and sticking. Manufacturers cut these prepreg sheets to precise shapes and lay them up onto a mold surface. The layered structure is then consolidated, often under heat and pressure in an autoclave or oven, to complete the curing process of the resin. This allows for controlled fiber orientation and high fiber volume fractions, leading to superior mechanical properties. Prepreg technology is widely used in industries requiring high-performance lightweight structures, such as aerospace, automotive, and sporting goods.