A composite material is a material in which two or more materials are combined to form physically and chemically different phases to express more effective functions. According to the structure of the reinforcing material, it is divided into fibrous composite, particulate composite, and polymer composite, metal composite, and ceramic composite according to the reinforcing material (matrix).
In the sense of mixing two or more materials, it can be compared to an alloy material. As shown in the table, an alloy material is a chemical mixture, in which the properties of the existing material are destroyed, new crystals are formed, and the microstructure is homogeneous, while a composite material is a mechanical mixture, in which the existing material is preserved and has its own mechanical properties. In addition, the microstructure is relatively inhomogeneous. These composites are a mixture of the properties of both materials, which allows for flexibility in material design.
| Alloy Materials | Composite materials | |
| Mixing | Chemical Mixing | Mechanical Mixing |
| Features | Existing material disappears | Existing substance is preserved |
| Microstructure | Homogeneous | Relatively inhomogeneous |