ABSTRACT
Compression molding is one of the oldest composite manufacturing processes and is now widely used for making Polymer Matrix Composite (PMC) parts using sheet molding compounds (SMCs) and bulk molding compounds (BMCs) as the starting material. This chapter describes SMCs and BMCs. It also discusses the compression molding process, flow and cure characteristics, and other topics related to it. SMC is a continuous sheet of ready-to-mold material containing fibers and mineral fillers dispersed in a highly viscous, but uncured thermosetting resin. The principal steps in the production of an SMC sheet include mixing, compounding, compaction, and maturation. BMC is also a ready-to-mold short fiber-reinforced thermoset used for compression molding and injection molding. The flow pattern of the SMC material during compression molding is a key factor in determining the quality of the molded part. It determines not only the extent of mold filling, but also the defects that may be caused by uneven or interrupted flow.
