ABSTRACT
Thermoset resins are very conducive to processing, as their viscosity is reasonably low to allow easy impregnation of the empty spaces between the fiber preforms. The earliest composites manufacturing concentrated on processes such as wet hand lay-up, which is an open mold process. This process employed a one-sided male or female mold, in which a layer of resin, called the gel coat, is applied on the mold surface. The gel coat is usually about 0.5 mm in thickness, has good environmental resistance and produces a smooth and pigmented surface that covers the fiber preform. To manufacture a composite, a measured amount of the thermoset resin is poured over the gel-coated surface. The fiber preform is placed on top of the liquid resin and pressed by a hand-held roller. The resin percolates through the fibrous network due to the application of the pressure as shown in Figure 8.1.
