Q: 15 years ago, people wondered if SMC materials can compare with the strength of ductile iron?

A: When so-called SMC manhole cover first appeared on the market, there were manhole covers with DMC and reinforced steel bars on the Chinese market. In China, India, and Central African countries, this kind of manhole cover was molded by a few scrap steel bars inside and waste medium-alkali glass fiber and garbage red resin on the outside. Manhole cover, no matter how thick the internal steel bar is, the two materials cannot be combined, and they will be separated after long-term rolling by vehicles, and the steel bar will rust after being wet. The medium-alkali glass fiber will be alkalized after encountering acidic rainwater, and holes will appear on the surface of the manhole cover. SMC is made of alkali-free long glass fiber into a balanced sheet through professional equipment, bonded with high-end resin, and formed in a mold under high temperature and high pressure. The same material is not subject to various stress and thermal expansion changes due to changes in external temperature. The special glass fiber, process and structural design make SMC manhole covers have super-strength load-bearing capacity, and their cost performance exceeds that of ductile iron. Cast iron is easy to steal and makes impact sounds when vehicles pass by. The surface of cast iron needs to have a layer of anti-rust treatment, whereas SMC manhole covers can be produced in any color without fading.

During the construction of SMC manhole cover, the manhole built by the worker must not be larger than clear opening of the manhole cover , in other worlds, the minimum size of the manhole cover base cannot be built into an irregular manhole, which is easy to cause damage to the base. The requirements are much higher than those of cast iron. Cast iron is called smelting chemical forming, while SMC is physical forming by glass fiber molding, and the stress deformations are different chemistry.

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