The most common multifunctional composite material itself is not only a structural material but also has other functions. For example, the fuselage of the stealth aircraft is made of carbon fiber or silicon carbide fiber reinforced epoxy resin and ferrite filler, especially the composite with honeycomb sandwich, which is itself a lightweight and high-strength structural material. Once the electromagnetic wave (radar wave) hits the fuselage. Absorb part of the surface layer first and make the penetrating wave scatter and absorb several times in the interlayer to avoid radar search and achieve stealth: multi-functional composite materials came into being with the requirements of military high-tech, and have gradually turned to civilian use, such as the water reservoir of solar heater, which is made of composite materials with waterproof structure and radiation heat absorption. [1]
