9.6 : Composite Bodies

A composite body is a body made up of multiple parts, connected to form a larger, unified object. Each part has its own weight and center of gravity, which must be considered to determine the center of gravity of the composite body. In cases where the density or specific weight is constant, the center of gravity coincides with the centroid.

Composite bodies have widespread applications in mechanical engineering, from automobiles to aircraft to rockets. For example, an automobile wheel comprises a rim and spokes connected to form a single unit. Calculating its center of gravity requires knowledge about the individual parts' weights and center of gravity locations. Similarly, an aircraft wing may consist of multiple components, such as ribbing and spars, which can also be considered composite bodies. Once these parts have been accounted for, a calculation can be done to determine the aerodynamic center, which affects how the wing performs in flight. Another application is in rockets, where composite materials are used for fuel tanks due to their lighter weight compared to other options. By determining the center of gravity accurately, engineers can reduce vibration and enhance stability during launch.