COMMON METALLIC MATERIALS

Figure 1-20.—Engine torque creates torsional stress in aircraft fuselages. Figure 1-21.—Bending action occurring during carrier landing. An aircraft requires materials that must be both light and strong. Early aircraft were made of wood. Lightweight metal alloys with a strength greater than wood were developed and used on later aircraft. Materials currently used in aircraft construction maybe classified as either metallic or nonmetallic. COMMON METALLIC MATERIALS The most common metals in aircraft construction are aluminum, magnesium, titanium, steel, and their alloys. Aluminum alloy is widely used in modern aircraft construction. It is vital to the aviation industry because the alloy has a high strength-to-weight ratio. Aluminum alloys are corrosion-resistant and com- paratively easy to fabricate. The outstanding character- istic of aluminum is its lightweight. Magnesium, the world’s lightest structural metal, is a silvery-white material weighing only two-thirds as much as aluminum. Magnesium is used in the manufacture of helicopters. Magnesium’s low resistance to corrosion has limited its use in con- ventional aircraft. Titanium is a lightweight, strong, corrosion- resistant metal. It was discovered years ago, but only recently has it been made suitable for use in aircraft. Recent developments make titanium ideal for applications where aluminum alloys are too weak and stainless steel is too heavy. In addition, titanium is unaffected by long exposure to seawater and marine atmosphere. An alloy is composed of two or more metals. The metal present in the alloy in the largest portion is called 1-21