

Microwave Curing of Long Fiber Reinforced Composites for Resin Transfer Moulding
Abstract
In the present work, microwave radiation has been employed in order to polymerize the resin of long fibre reinforced composites [1]. The research carried out in microwave processing [2] contributes to the following benefits to the composite processing: • Multi-functional polyester, vinyl-ester and epoxy resins suitable for RTM process and microwave curing have been modified. The determination of the dielectric function of the resin and the assessment on microwave susceptors suitable to enhance the curing time is included. They have low viscosity for optimal filling of the mould. After the filling process was completed, a three dimensional microwave system is applied to start the curing of the resin. The curing is an exothermic reaction, so that the microwave only initiated the curing. • This innovative microwave system in connection with a temperature control system ensures a homogenous heating and therefore optimal curing of the resin. The microwave system is developed with the help of simulation software for the microwave field and resulting heating. • The degree of polymerisation of the resin is increased by microwave radiation and the polymerisation degree was close to 100% with a reduction in curing time. Because of the very high degree of polymerisation the styrene emission, particularly during demoulding, can be decreased more than 80%, compared to open mould processes. Process parameters were also studied and compared to the traditional heating process. A cost effective method for composites manufacturing by RTM has been developed. A scaleable microwave system adapted to RTM is being developed for homogenous heating and therefore curing of composite parts. Only the combination of the developed resins and the microwave system with a temperature control ensured a homogenous processing of the part.