| 摘要 |
Some previously proposed lids or covers for utility vaults are made from concrete, polymer concrete and cast iron to withstand loads. A drawback of these cover types is that they are quite heavy. Due to their weight, they are difficult to remove for repair, maintenance or adding additional services. Utility vault and pit cover lids are also made of plastic but these have limited application for use in areas where they are subjected to less load. The problem with plastic lids is that because they cannot withstand substantial loads, they have limited applicability and plastic lids provide less coefficient of friction when wet versus polymer covers. A method of manufacturing a fiber reinforced composite material lid for an utility vault includes mixing an unsaturated polyester thermosetting matrix in to a resin paste, compounding the resin paste into a fiber reinforced composite material, maturing the compounded fiber reinforced composite material, cutting the matured compound into a charge pattern, molding the charge pattern in a mold cavity of a heated mold under low pressure to form the lid, the molding step including pushing fibers in the charge pattern away from a surface of hte lid to create a resin rich textured surface, and cooling and machining the lid. The mold includes a cavity die and a core die having a shear angle for interfacing the core die within the cavity die and a steam pot for heating the cavity die and the core die, wherein the lid is molded between the cavity die and the core die and removed from the mold by a lid ejection mechanism. |
