Composite materials are pervasive throughout our world and include both natural and man-made composites. For example, in nature, wood is a composite consisting of wood fibers (cellulose) bound together by a matrix of lignin. Composite materials have been used by mankind for thousands of years; many of the sun-dried mud brick buildings of the earliest known civilization in Mesopotamia at Sumer were reinforced with straw as early as 4900 B.C. However, with the advent of high-strength man-made fibers and the tremendous advances in polymer chemistry during the twentieth century, in many instances composite materials now can be made that offer advantages comparable to those of competing materials. The advantages of these advanced composites are many, including lighter weight, the ability to tailor composites for optimum strength and stiffness, improved fatigue life, corrosion resistance, and, with good design practice, reduced assembly costs due to fewer detail parts and fasteners.