First of all, the strength and stiffness of composite materials are significantly improved by the introduction of reinforcing materials. For example, carbon fiber reinforced plastic (CFRP) is famous for its high specific strength and high specific stiffness, and is widely used in airplane wings and racing car bodies. In these composites, high-strength fibers as reinforcing phase can effectively bear external forces, while the matrix plays the role of fixing and protecting the fibers, so as to optimize the overall performance.

Secondly, the composite material has good fatigue resistance. Traditional metal materials are prone to fatigue cracks under cyclic loading, while composite materials can effectively prevent crack propagation and improve the service life of materials because of their multiphase structure and anisotropic characteristics. For example, the blades of wind turbines are mostly made of glass fiber composite materials, which not only reduces the weight, but also significantly improves its reliability under long-term alternating loads.
　　In addition, the design flexibility of composite materials is also an important factor to improve the mechanical properties. The directional optimization of material properties can be realized by reasonably selecting the types, proportions and layering methods of matrix and reinforced materials. This designability enables the composite materials to be customized according to different application requirements, so as to obtain the best mechanical performance in a specific direction.

Finally, the composite material also has excellent corrosion resistance and wear resistance, which is especially important in harsh environment. Compared with traditional metal materials, it is easy to be oxidized and corroded. Composite materials can maintain stable mechanical properties in humid, high-temperature or chemical corrosive environments and prolong the service life of equipment.
　　To sum up, composite materials show significant advantages in improving material strength, stiffness, fatigue resistance and durability through their unique structural composition and designability. With the continuous progress of materials science and engineering technology, composite materials will play an irreplaceable role in more fields and provide strong support for the development of modern industry.