The fibre reinforced plastics can be manufactured using a wide range or production methods. Open casting techniques, such as hand lay-up processes, are often used by small companies or for very limited part series. Open laminating techniques require intensive manual labour resulting in high part costs and low output. For high volume series, closed casting processes are advantageous with respect to production technology, production costs, end product properties, and environmental compatibility. The most commonly used closed casting processes are compression moulding, resin infusion (RI), and resin transfer moulding (RTM).
The most important compression moulding techniques is based on SMC (sheet moulding compounds). SMC can, however, only be used for large volume applications where the high mould and machine related costs can be justified.
Resin transfer moulding (RTM resin injection) represents an approach that is technically and economically advantageous for production volumes between those of open casting and SMC. Further, RTM can also be used for sandwich constructions.