Introduction

The first chapter introduces the major concept of composite material, i.e., the combination of different components, to obtain in total much better properties than a single component for itself. The focus is on fiber-reinforced composites where a single layer has unidirectionally aligned reinforcing fibers. The second part of this chapter introduces the concept of reference numbers, which are commonly used to predict and characterize the properties of composites depending on their composition. The common approaches are related to the volume, mass, or relative density.