1. The thermal expansion of plastic raw materials, the coefficient of linear expansion is much larger than that of metal;
2. The stiffness of general plastic raw materials is an order of magnitude lower than that of metal;
3. The mechanical properties of plastic raw materials will be significantly reduced under prolonged heating;
4. General plastic raw materials will be permanently deformed under long-term stress at room temperature and under a stress lower than its yield strength;
5. Plastic materials are very sensitive to notch damage;
6. The mechanical properties of plastic raw materials are usually much lower than those of metals, but the specific strength and specific modulus of some composite materials are higher than those of metals. If the product design is reasonable, it will be more advantageous;
7. Generally, the mechanical properties of reinforced plastic raw materials are anisotropic;
8. Some plastic materials will absorb moisture and cause changes in size and performance;
9. Some plastics are flammable;
10. The fatigue data of plastic raw materials is still very small, and it needs to be considered according to the requirements of use.
