With the acceleration of urbanization and the balance and protection of population, resources, and environment, governments at all levels have increased their investment in urban infrastructure year by year. In combination with the needs of advanced science and technology, the varieties and specifications of pipes and fittings are continuously enriched. With the continuous increase and the continuous improvement of quality, especially the development of plastic pipes, FRP Pipe is one of them.
FRP Pipe also encounters these common problems when it is used:
1. Low stiffness and strength. The elastic modulus of FRP is twice as large as that of wood, but 10 times smaller than steel (E=2.1×106). Therefore, it is often insufficient in rigidity and easy to deform in the product structure. When FRP is used in water, especially in salt water for a long time, due to salt water. The penetration and the swelling of the FRP will significantly reduce the strength of the FRP and eventually lead to damage.
2. FRP Pipe also undergoes “corrosion”, but the difference from the corrosion phenomenon of ordinary carbon steel is that the “corrosion” of FRP Pipe is manifested by the deterioration of the material, and the performance of FRP Pipe after water absorption, swelling, and aging. The drop is the corrosion category of FRP. For FRP Pipe, the water absorption and even the wall thickness are slightly increased, but the FRP Pipe material and properties have been seriously attenuated, even to the extent that it is unusable.
3. The thermal expansion coefficient of FRP is large. The coefficient of thermal expansion of FRP is much higher than that of carbon steel (about two orders of magnitude higher). In long-distance FRP Pipe in areas with large temperature difference, the damage of FRP Pipe caused by thermal expansion and contraction caused by temperature difference must be considered.
4, long-term temperature resistance is poor. Generally, FRP cannot be used for a long time at a high temperature. The strength of general-purpose polyester FRP is obviously lower at 50 °C, and the strength of general-purpose epoxy FRP is above 60 °C.
5. Aging phenomenon. Aging is a common defect of plastics. FRP is no exception. It is easy to cause performance degradation under the influence of ultraviolet light, wind, rain, snow, chemical medium, and mechanical stress.
6. The interlaminar shear strength is low. The interlaminar shear strength is borne by the resin and is therefore very low.
7. Construction quality. Another key issue with FRP Pipe is the processing of field interface. At present, the interface quality problem is very prominent in China's FRP construction projects, especially for long-distance pipelines, the number of interfaces is large, and the quality of interface processing directly affects the quality of the entire project.
