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What is Molded Manhole Cover?

What is molded Manhole Cover?
The molded manhole cover is formed by adding the molding compound to the steel bar under a certain temperature and pressure. The manhole cover is made of short fibers (30-50mm short fiber forming composite material has a strength of only 20-30% of continuous fiber), and the bottom cover structure is slab bottom rib, which is caused by the reinforcement material and the manhole cover structure. The bearing capacity of the manhole cover is seriously insufficient, and only steel bars can be added to increase the load.
The addition of steel bars has two major defects: 1 rust on the surface of the steel bar, which often leads to poor bonding of the material interface (if the interface of the composite material is not well combined, it will not produce 1+1>2 effect); Metal materials, SMC/BMC are non-metallic materials, and the two materials differ in thermal expansion coefficient. At different temperatures (early, medium, late, winter, summer), the material interface will form stress, and repeated rolling of the vehicle will cause the steel bar to detach from the SMC/BMC, which will eventually lead to the loss of bearing capacity of the manhole cover. The ability depends on the compounding process and conditions of use in the production process, perhaps 2-3 years, maybe longer). Advantages: A, anti-theft; B, exquisite appearance; Disadvantages: A, insufficient carrying capacity; B, due to the addition of steel bars, the interface will be detached, resulting in loss of carrying capacity.

composite manhole cover
The composite composite manhole cover is made of unsaturated polyester resin as the base material, and the glass fiber is used as the reinforcing material, supplemented by a certain rigid material. The structure of the bottom of the pot is adopted, and the bottom tensile material is evenly stressed; the material is divided into upper and lower layers, and the upper part is made of wear-resistant and aging-resistant materials, and the product has a long service life. The lower part is reinforced with continuous glass fiber, which allows the manhole cover to have sufficient load carrying capacity without any reinforcement. It is a material manhole cover with better comprehensive performance in several composite manhole covers. Advantages: A, anti-theft; B, high carrying capacity; C, beautiful appearance. Disadvantages: A, the surface hardness is high, and the brittleness is slightly higher; B, the price is slightly higher.
Molded manhole cover: It is made of unsaturated resin as the basic material, using 30-50mm short fiber and steel bar as reinforcing material, using calcium carbonate as filling material and pressing at a certain temperature. Since the steel bar is a metal material and the BMC is an organic material, the thermal expansion coefficient of the BMC is twice that of the steel bar, and the interface of the BMC is not firmly bonded when the steel plate is rusted. When the temperature changes, the steel bar and the BMC material are changed. The interface will form stress, and the repeated rolling of the vehicle will cause the steel bar to separate from the BMC interface, and finally the cover will lose its bearing capacity. And the surface is a mixture of BMC and calcium carbonate materials, and thus the wear resistance is poor.
Glass fiber reinforced composite manhole cover: The structure of the bottom of the glass is adopted from the structure (uniform bearing). Compared with the ribbed type (concentrated bearing), the area of the bottom is increased by several times. Secondly, the layer is reinforced and layered. Interlocking, uniform force, therefore, the structure makes the product bearing capacity stronger; from the material aspect, the wear layer uses multi-color quartz sand as wear-resistant material and adds stabilizer, so that the service life of the product is doubled; The use of continuous reinforcing fiber skeleton ensures high load-bearing capacity of the product, while other composite manhole covers do not use fiber reinforcement, even if fiber reinforcement is used, short fibers (short fiber strength is only 20%-30% of continuous fiber). When the strength is not enough, it has to be compensated by steel bars. The whole material of the product is organic material. Different reinforcing materials are used in different parts of the manhole cover, which avoids the separation and shedding phenomenon of other composite materials due to the use of reinforcing materials such as steel bars. The layered composite process is adopted to meet the requirements of institutional innovation and material innovation, and different reinforcing materials are used in different parts of the manhole cover to separate and fall off the different parts of the manhole cover using different reinforcing materials.

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