Introduction

Structural materials can be divided into four basic categories: metals, polymers, ceramics, and composites. Composites, which consist of two or more separate materials combined in a structural unit, are typically made from various combinations of the other three materials. In the early days of modern man-made composite materials, the constituents were typically macroscopic. As composites technology advanced over the last few decades, the constituent materials, particularly the reinforcement materials, steadily decreased in size. Most recently, there has been considerable interest in “nanocomposites” having nanometer-sized reinforcements such as carbon nanoparticles, nanofibers, and nanotubes, because of the extraordinary properties of these materials.