Composites as Biomaterials

Composite materials are those that contain two or more distinct constituent materials or phases, on a microscopic or macroscopic size scale. The term “composite” is usually reserved for those materials in which the distinct phases are separated on a scale larger than the atomic, and in which properties such as the elastic modulus are significantly altered in comparison with those of a homogeneous material. Accordingly, fiberglass and other reinforced plastics as well as bone are viewed as composite materials, but alloys such as brass or metals such as steel with carbide particles are not. Natural biological materials tend to be composites; these are discussed in Chapter 9. Natural composites include bone, wood, dentin, cartilage, and skin. Natural foams include lung, cancellous bone, and wood. Natural composites often exhibit hierarchical structures in which particulate, porous, and fibrous structural features are seen on different length scales. In this chapter, composite material fundamentals and applications in biomaterials are explored.