Properties of composite materials

Fiber reinforced materials are the most widely used and used in composites. It is characterized by small specific gravity, large specific strength and specific modulus. For example, the composite material of carbon fiber and epoxy resin has a specific strength and specific modulus several times larger than that of steel and aluminum alloy, and also has excellent chemical stability, antifriction and wear resistance, self-lubrication, heat resistance, fatigue resistance, creep resistance, noise elimination, electrical insulation and other properties. The composite of graphite fiber and resin can obtain materials with thermal expansion coefficient almost equal to zero. Another characteristic of fiber reinforced materials is anisotropy, so the arrangement of fibers can be designed according to the strength requirements of different parts of the parts. The aluminum matrix composites reinforced with carbon fiber and silicon carbide fiber can still maintain sufficient strength and modulus at 500 ℃. The composite of silicon carbide fiber and titanium can not only improve the heat resistance of titanium, but also wear resistance, and can be used as engine fan blades. The service temperature of silicon carbide fiber and ceramic composite can reach 1500 ℃, which is much higher than that of superalloy turbine blade (1100 ℃). Carbon fiber reinforced carbon, graphite fiber reinforced carbon or graphite fiber reinforced graphite constitute ablative materials and have been used in spacecraft, rocket missiles and nuclear reactors. Due to its low density, non-metallic matrix composites can reduce weight, improve speed and save energy when used in automobiles and aircraft. The composite sheet spring made of carbon fiber and glass fiber has the same stiffness and bearing capacity as the steel sheet spring with more than 5 times the weight.