What are composite materials and why are they used in aircraft?

Composite materials combine two or more constituent materials (typically fiber reinforcement in a polymer matrix) to achieve properties superior to individual components. In aircraft, carbon fiber reinforced polymer (CFRP) is most common. Advantages include: high strength-to-weight ratio (30-40% lighter than aluminum for equal strength), excellent fatigue resistance, corrosion immunity, ability to tailor directional properties, and complex shape manufacturing. The Boeing 787 and Airbus A350 use over 50% composites by weight in their structures.