Sheet molding compound (SMC) is a combination of uncured thermoset resins, fillers, additives and long glass fibers, in sheet form, that is used to make glass reinforced plastic (GRP) products. It is formed into products by compression molding. Compression molding involves placing a sheet of SMC onto a heated mold, then forcing it into the mold cavities using a heated plug. Heat from the plug and mold softens the SMC and allows it to flow into the mold cavities. After a few seconds, the heat begins to cure the SMC, which solidifies and hardens.
These materials are usually formulated to meet performance requirements of the part to be molded. SMC is ideal for large structural components due to its high strength-to-weight ratio, thermal resistance, good mechanical and electrical properties, decreased shrinkage, sink marks and warpage. SMC offers additional benefits in part design allowing localized rib reinforcement and bosses for fastening attachments and sub-assemblies. Significant tooling investment and overall component cost savings result from part consolidation. With the same coefficient of thermal expansion as Steel and excellent corrosion resistance, SMC is an ideal alternative to Steel and can be used in the same fluctuating temperature environments. The main benefit however is a typical 25% weight reduction achieved at similar strength to Steel.
Various types of SMC sheets and parts with different applications such as automotive, flame retardants, food grades and etc., are being designed and manufactured by the companies in this industrial group.