Which materials are commonly used for airframe structural members?

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Airframe structural members need to be light yet very strong, with good stiffness, damage tolerance, and durability in service. Modern aircraft achieve this mainly with aluminum alloys, titanium, and composite materials like carbon fiber-reinforced polymers. Aluminum alloys are used widely because they blend light weight with adequate strength and formability, plus corrosion resistance when protected, making them ideal for skins, frames, and rib structures assembled by rivets or bonding. Titanium offers even higher strength-to-weight and excellent high-temperature and corrosion resistance, so it’s chosen for parts exposed to higher loads or temperatures, such as certain fittings, fasteners, and sections near the engine or under high stress. Composites, especially carbon fiber-reinforced polymers, deliver very high strength and stiffness at a fraction of the weight and have excellent fatigue performance; they’re used in primary structures to save weight, but require different manufacturing, inspection, and repair approaches and carry higher material costs. Wood and canvas were common in early aircraft but are not representative of modern airframes due to limited strength, durability, and damage tolerance. Ceramics and glass fibers are brittle and not suitable for primary load-bearing airframe members. Plastic laminates exist in some applications but are not the sole basis for modern airframe structures.