What is prepreg and how is it used in composite manufacturing?

Prepreg is fiber reinforcement pre-impregnated with resin matrix. Composition: Reinforcement - Carbon, glass, or aramid fibers in unidirectional tape or woven fabric; Matrix - Typically epoxy (aerospace) or BMI (higher temperature), partially cured (B-staged). Advantages: Consistent fiber-resin ratio, Controlled properties, Cleaner layup process, and High-quality laminates. Processing: Store frozen (-18C) to prevent cure advancement, Thaw before use, Layup on mold per ply schedule, Vacuum bag, and Autoclave cure (temperature + pressure, typically 180C, 100 psi). Characteristics: Out-time limit (working life at room temperature), Tack (stickiness for layup), and Drape (conformability to complex shapes). Types: Unidirectional tape (highest properties, efficient layup), Woven fabric (drapeable, impact resistant), and Spread tow (thin plies, reduced weight). Prepreg is the dominant form for aerospace composite primary structure. Quality control includes fiber areal weight, resin content, and tack/drape testing.