tailieunhanh - Composites Manufacturing - Materials, Product, and Process Engineering Part 7

Tham khảo tài liệu 'composites manufacturing - materials, product, and process engineering part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | is not as crucial spray-up is the more suitable option. Bathtubs swimming pools boat hulls storage tanks duct and air handling equipment and fur- niture components such as seatings are some of the commercial uses of this process. Basic Raw Materials The reinforcement material for this process is glass fiber rovings which are chopped to a length of 10 to 40 mm and then applied on the mold. For improved mechanical properties a combination of fabric layers and chopped fiber layers is used. The most common material type is E-glass but carbon and Kevlar rovings can also be used. Continuous strand mat fabric and various types of core materials are embedded by hand whenever required. The weight fraction of reinforcement in this process is typically 20 to 40 of the total weight of the part. The most common resin system used for the spray-up process is generalpurpose or DCDP polyester. Isophthalic polyester and vinylesters are also used in this process. Fast-reacting resins with a pot life of 30 to 40 min are typically used. The resin often contains a significant amount of filler. The most common fillers are calcium carbonate and aluminum trihydrate materials. In filled resin systems fillers replace some of the reinforcements 5 to 25 filler is used by weight. Tooling Requirements The mold used in this process is identical to that used in the wet lay-up process. Male and female molds are used depending on the application. Tubs and showers utilize male molds whereas boat hulls and decks utilize female molds. To make bathtubs FRP molds are used. The method used to make the mold is described in Section . Making of the Part The processing steps used in the spray-up process are very similar to those in the wet lay-up process. In this process the release agent is first applied to the mold and then a layer of gel coat is applied. The gel coat is left for 2 hr until it hardens. Once the gel coat hardens a spraygun is used to deposit the fiber resin .